1

Chapter One: Introduction

Figure 1.1: Villanova University Constructed Stormwater Wetland (View from Upstream/Inlet Looking Downstream/Outlet)

1.1 Introduction

The primary purpose of the present study is to analyze the pollutant removal efficiency o

the Villanova University Constructed Stormwater Wetland (CSW) during both times of baseflow

and storm events. This research analyzes the presence of a trend in the pollutant removal

efficiencies throughout the different seasons of the year as well as in the removal efficienci

between the different pollutants. Additionally, while not part of this present research, the data

collected and analyzed add to the body of nutrient data for this CSW. A secondary aspect of the

study is the investigation of plant effects on the removals. Factors that impact nutrient removal

include the flow path, retention time, plant density and plant type. The Villanova University

CSW has a Phragmites australis invasion problem. Although P. austra

f

es

lis is very efficient at

moving nutrients, control regimes are used to remove P. australis from the CSW in order to

ival of the native plants. This poses a question: If P. australis is

re

allow for the continued surv

2

effective at removing pollutants, why should it be removed from the CSW? A second

component of the present study, a plot study, aims to answer this question. The plot study is a

series of plots within the CSW with different plant types. As flow moves through each plot,

as surface water and groundwater, nutrients may be removed through physical, chemical and

biological action. Another question addressed in the plot study is: Are nutrients removed

through the plots? To answer these questions, the study will test the hypothesis of: A species

diverse CSW is more effective at removing pollutants than a P. australis dominated CSW. If th

studies show that native plants are just as or more effective at pollutant removal than P. austral

then P. australis control programs would be more substantiated, and the goal of maintaining a

species diverse CSW will receive an even larger desire for realization.

1.2 General Background

The objective o

both

e

is,

f the present study is to examine the nutrient removal efficiency of a

d Wetlands

rest

m

ars time will be analyzed in order to assess the functioning and seasonal performance

f a ma

ivil

rmwater

artnership (VUSP) in 2002. The mission of the VUSP is to foster the developing

omprehensive stormwater management field as well as aide the formation of public and private

partnerships through research on stormwater Best Management Practices (BMPs), directed

studies, technology transfer and education. The VUSP manages a collective research effort on a

functioning CSW. Constructed stormwater wetlands (CSWs) are designed to remove pollutants

from stormwater runoff via a variety of mechanisms: plant uptake, microbial breakdown of

pollutants, retention, settling and soil adsorption (Metropolitan Council, Constructe

Stormwater Wetlands, 2001). CSWs have low operating and maintenance costs, and they are

also aesthetically pleasing (EPA, Constructed Treatment Wetlands, 2004). The CSW of inte

is a green infrastructure located on the campus of Villanova University (Figure 1.1). Previous

studies have been performed on this CSW addressing the removal efficiencies during times of

storm events and baseflow (Rea, 2004; Woodruff, 2005). Both storm and baseflow events fro

over a ye

o ture CSW. The pollutants of interest in the removal studies are: total nitrogen, total

phosphorus, total orthophosphate, total chloride, total suspended solids, and total dissolved

solids.

The Pennsylvania Department of Environmental Protection and the Department of C

and Environmental Engineering of Villanova University created the Villanova Urban Sto

P

c

3

variety of stormwater BMPs both on and in the vicinity of Villanova Universitys campus in

Villanova, Pennsylvania (VUSP Mission, 2008); one such BMP is the Villanova University

CSW.

The Villanova University CSW was retrofitted from an existing dry detention basin

(Figure 1.2) in October of 1999 with an EPA 319 Program grant from the Pennsylvania DEP

(Stormwater Wetland Project Report, 2008). This detention basin acted more like a detention

pond, which treated stormwater flows from both the main and west campuses of Villanova

University, totaling an approximate total drainage area of 56.6 acres (Woodruff, 2005).

Figure 1.2: Original Dry Detention Basin (Rea, 2004; Stormwater Wetland Project Report, 2008)

Water quality considerations were not taken into account in the original design of the dry

detention basin (Figure 1.3). Th

e basin was designed with the intended purpose of reducing and

managing stormwater runoff flows from Villanovas campus. Runoff entered the basin from two

inlet pipes and sheet flow from a parking lot. (EPA, Section 319 Success Stories, 2007) The dry

detention basin was constructed with an outlet structure designed to pass the 25, 50 and 100-year

storms (Woodruff, 20 basin dry during

periods of non-storm events. However, it was discovered that even though the basin would

05). It was built with a 12 inch underdrain that kept the

4

remain dry, there was baseflow throughout the year in the underdrain, even during the summer

ce of the baseflow may be from a series of natural springs. The constant

baseflo ter

1999 drought; the sour

w made the site an ideal location for the creation of a stormwater wetland. (Stormwa

Wetland Project Report, 2008)

Figure 1.3: Plan of Original Dry Detention Basin (Stormwater Wetland Project Report, 2008; Woodruff, 2005)

1.3 Site Retrofitting

The design concepts presented in the Pennsylvania Handbook of Best Management

Practices for Developing Areas (Pennsylvania Association of Conservation Districts, 1998) were

used during the retrofitting of the dry detention basin into the CSW. The retrofit of the dry

detention basin concentrated on retaining small storms while simultaneously not violating the

original stormwater peak flow controls mandated by law (EPA, Section 319 Success Stories,

2007). The CSW maintained the basins ability to moderate the two to 100-year storms, but it

also became a water quality treatment facility (Woodruff, 2005). The underdrain of the basin

was removed in order to allow for baseflow, wh h is a critical part of the CSW, to flow

throughout the ba dering wetland

ic

sin. Earthen materials were shaped into berms to create a mean

5

channel in order to in bay was created in

order to allow for suspended particles to settle ou the water column. (Stormwater Wetland

In addition, the CSW was planted with a diverse selection of native

crease flow path distance (Figure 1.4). A sediment fore

t of

Project Report, 2008)

wetland plants (EPA, Section 319 Success Stories, 2007).

Figure 1.4: Design Plan for the Villanova University CSW (Stormwater Wetland Project Report, 2008; Woodruff, 2005)

1.4 Site Description

The Villanova University CSW receives stormwater runoff from a 57 acre watershed;

approximately 32 acres of impervious surfaces such as parking lots, dormitories, school

buildings, railroads, highways and housing areas; approximately 16 acres of semipervious

rfaces, such as lawns; approximately seven acres of the watershed is made of pervious surfaces

such as trees; approximately one acre of the watershed consists of the CSW itself (Jones, 2008).

The CSW consists of two inlets, a sediment forebay, a meandering channel and an outlet

structure.

su

6

ke up the inlet

tructure

nal to the

reten

lined with wetland plants, which help to increase roughness and promote friction between the

water flow and land, thus Wetland Project

Report, 2008) Low velocities allow

g Channel Flow Path 04; St Wetlan rt, 20

The inlet structure of the original dry detention basin was not altered during the

retrofitting of the site into the current CSW (Figure 1.4). Two main inlet pipes ma

structure of the CSW.

The sediment forebay was an addition during the retrofit of the dry detention basin

(Figure 1.4). The main purpose of the sediment forebay is to capture the sediment loads and

prevent them from exiting the CSW (Davis, 1995). It was placed offline from the outlet s

to aid in the prevention of resuspension.

The meandering channels were created during the retrofit of the dry detention basin

(Figure 1.5). The ability of a CSW to efficiently remove pollutants is directly proportio

tion time of the water. In order to increase the waters retention time, meandering channels

were created to extend the flow path of water through the CSW. The meandering channels were

constructed with a minimal channel slope to allow for low velocities. The channels were also

creating low water flow velocities. (Stormwater

an increase in the retention time of water in the CSW, which

increases the pollutant removal efficiency. (Kadlec, 1995)

Figure 1.5: Meanderin(Rea, 20 ormwater d Project Repo 08)

7

The outlet structure of the original dry detention basin was alter g the construction

of the CSW (Figure 1.4). The outle ned with the purpose of maintaining the existing

flood control functionality while still s ricting low flows. (Stormwater

Wetland Project Report, 2008)

1.5 Wetland Plan

One of the goals in creating CSWs is to generate dense, diverse vegetation that mimics

that of nearby natural wetlands. The wetland plants are the h system as

they provide she t f w ita nt removal.

The plants selected (Table 1.1) are native to the south egion of ania, and their

growing requirem rop ions they w (Figure 1.4).

Table 1.1: Original Wetland Plant List

Common Name Scientific Name Common Name Scientific Name

ed durin

t was desig

upporting the CSW by rest

ts

earts of the wetland eco

lter and habita or organisms as ell as play a v l role in polluta

eastern r

in which

Pennsylv

ere plantedents are app riate to the locat

Sweet Flag Acorus calamus Arrow Arum

Peltandra

virginica

Swamp Milkweed

Asclepias

incarnata Pickerelweed

Ponteteria

cordata

New England Aster

Aster novae-

anglia Lizards Tail Saururus cernus

Blue-Joint Grass

Calamagrostis

canadensis

New York

Ironweed

Vernonia

noveboracensis

Fringed Sedge Carex crinata Smooth Alder Arnus serrulata

Lurid Sedge Carex lurida Red Chokeberry Aronia arbutifolia

Tussock Sedge Carex stricta Buttonbush

Cephalanthus

occidentalis

Blue Flag Iris Iris versicolor Sweet Pepperbush Clethra alnifolia

Cardinal Flower Lobelia cardinalis Silky Dogwood Cornus amomum

Blue Lobelia Lobelia siphilitica Blueberry angustifolium

Lowbush Vaccinium

8

1.5.1 Phragmites australis

Phragmites australis invasion is an ongoing problem in many CSWs, including that of

illanova University. P. australis is an invasive species with a high salinity tolerance that is

ense patches and is effective at removing pollutants from the CSW; however, it

utcom

; a

ngs

e

d its

reproductive rhizomes (Maryland Department of Natural Resources, 2008).

belief

.6 CS

is the part of the CSW discharge, not attributable to direct runoff from precipitation

instead sustained by groundwater and other daily sources of inflow.

.7 Research Objective The objective of this study is to examine the yearly pollutant removal trends seen in the

illanova University CSW. The removal efficiencies of each pollutant are analyzed on a

asonal and yearly basis during both times of baseflow and storm events. A plot study is used

order to gain a more thorough understanding of the differences in pollutant removal

efficiencies between native and invasive plant species. The results of the preliminary plot study

V

able to grow in d

o petes the native plants originally planted and species diversity has thereby decreased. To

maintain a species diverse CSW, it is imperative to control the rapid expansion of P. australis

control regime has been implemented which includes continuous cycles of glyphosate sprayi

and cuttings. Glyphosate, commercially known as Rodeo, is a broad spectrum aquatic herbicid

that is applied to the foliage of actively growing P. australis in order to kill the plant an

1.5.2 Plot Study

A plot study was conducted to compare the pollutant removal efficiencies of native

wetland plants and the invasive P. australis. The preliminary results demonstrate that a native

plant is equally or more efficient at removing nutrients than P. australis, supporting the

that a species diverse CSW is more effective at removing pollutants than a P. australis

dominated CSW. Consequently, these results give validity to a P. australis control plan.

1 W Flow

Direct runoff is overland flow that is caused by excess precipitation which is not stored in

depressions in the ground, intercepted, evaporated, transpired by plants or infiltrated into the

ground (Mays, 2005). The main source for direct runoff is precipitation from storm events.

Baseflow

events, which is

1

V

se

in

9

help to demonstrate the importance of maintaining a species diverse CSW: namely that

preventing the invasion of exotic species helps to increase the efficiency of a CSW as a whole.

Chapter Two has a review of the literatur ent to this study. Chapter Three

delineates the methods used in the present study. Chapters Four and Five review the results and

present a discussion on pollutant fate for storm and baseflow conditions, respectively. Chapter

Six describes the plot study. Chapter Seven presents conclusions and suggestions for future

studies.

e pertin

10

Chapter Two: Literature Review

2.1 Introduction

When the well is dry, we know the worth of water. Benjamin Franklin spoke these

wise words in 1746 in Poor Richards Almanac. Water is an infinitely valuable resource, and

steps must be taken to safeguard it for both ourselves and for future generations. The United

States has already taken many steps to protect its water resources. In 1948, Congress enacte

Federal Water Pollution Control Act, or Clean Water Act. This is the principal law which

governs pollution in the nations waters. In 1972, the Clean Water Act was revised and ame

with various programs for water qualit

d the

nded

y improvement. Many of these programs have thus been

xpanded and are still in use today. Further amendments were made to the Act in 1977, 1981

ment technology advancements, even more revisions might

be mad

e of fill

soil

etland Regulatory Authority, 2004)

2.3 Non

eric

e

and 1987, and with future water treat

e. (Copeland, 2002)

2.2 Regulations of Natural Wetlands

Section 404 of the Clean Water Act instituted a program to regulate the discharg

or dredged material into the waters of the United States. It regulates the depositing of sand,

and other fill materials into natural wetlands. Regulated water activities under this program

include: fill for development, water resource projects, infrastructure development, and mining

projects. Under Section 404, a permit must be received before dredged or fill material may be

discharged into wetlands. In order to receive a permit, one must demonstrate that steps have

been taken to avoid wetland impacts, to minimize the potential impacts on wetlands and to

provide compensation for any remaining unavoidable impacts. One such compensation is the

construction of artificial wetlands for the treatment of nonpoint sources of pollution. (EPA,

W

point Sources of Pollution

Nonpoint sources of pollution are the result of precipitation, land runoff, atmosph

deposition, infiltration, drainage, seepage, or hydrologic modification. As the runoff from

rainfall or melting snow moves across the ground, it collects and carries natural and human-made

pollutants and ultimately deposits them into lakes, rivers, wetlands, coastal waters and

11

groundwater. Section 319 of the Clean Water Act was passed in 1987 to launch a national

program which controls nonpoint sources of water pollution. (EPA, National Managemen

Measures to Protect and Restore Wetlands and Riparian Areas for the Abatement of Nonpo

Source Pollution, 2005) Although it is unrealistic to believe that all nonpoint source pollution

can be eliminated, the EPA recognizes that the use of BMPs is an acceptable method of reducing

nonpoint source pollution, as they are structural or nonstructural methods preventing or r

sediment, nutrients, pesticides and other pollutants from being transported between the land and

surface or ground water (Division of Forestry and Wildlife, Best Management Practices, 200

2.4 Best Management Practices

t

int

educing

7).

ed wetlands, retention systems, detention systems, and alternative outlet

esigns. (Metropolitan Council, Best Management Practices, 2001) These green infrastructures

al life support system - an interconnected network of waterways,

wetland

urces

essential and innovative conservation practice for the twenty-first century

(Bened

d to

n

There are two major types of BMPs: Runoff Pollution Prevention and Stormwater

Treatment. Stormwater Treatment BMPs, as used in this study, are effective in filtering

stormwater, reducing the speed at which stormwater leaves a site, and reducing the volume of

runoff. There are various kinds of Stormwater Treatment BMPs: infiltration systems, filtration

systems, construct

d

are: our nations natur

s, woodlands, wildlife habitats and other natural areas; greenways, parks and other

conservation lands; working farms, ranches and forests; and wilderness and other open spaces

that support native species, maintain natural ecological processes, sustain air and water reso

and contribute to the health and quality of life for Americas communities and people.

(Benedict and McMahon, 2002). Green infrastructure helps to restore and protect ecosystems by

supplying a blueprint for future development that promotes ecological, social and economic

benefits. It is both an

ict and McMahon, 2002).

The focus of this study is CSW BMPs. CSWs are artificial wetland systems designe

maximize the removal of pollutants from runoff through various methods: microbial breakdow

of nutrients, plant uptake, retention, adsorption and settling (Metropolitan Council, Constructed

Wetlands Stormwater Wetlands, 2001). The function and design of CSWs emulates that of

natural wetlands.

12

2.5 Natural Wetlands

A wetland is a region that is covered by shallow water and supports vegetation ad

for life in saturated soil conditions. Wetlands are a habit

apted

at for an extensive variety of plants and

nimals, and they also provide numerous services to mankind. They are dubbed natures

tland plants helps to improve the quality of water as it

flows t t

by storing water during and after a rain event (EPA,

Econom ds

structed Stormwater Wetlands

ir

e runoff and the CSW, the greater the amount of pollutant removal. CSW design

a

kidneys because the filtering action of we

hrough them (National Centre for Tropical Wetland Research, 2001). Wetlands intercep

water runoff and retain excess nutrients and pollutants that come from fertilizers, manure and

municipal sewage.

The dense plant cover of wetlands intercepts overland flow, which helps to protect

against soil erosion and sediment buildup (National Centre for Tropical Wetland Research,

2001). Wetlands act like natural sponges

ic Benefits of Wetlands, 2006). The water storage and retention capacities of wetlan

help to control floods. Wetland vegetation slows the velocity of flood waters and distributes

them in a more evenly fashion over the floodplain. Wetlands that are not filled to capacity with

storage water reduce flood peaks and slowly release floodwaters to downstream areas. The

water retention and storage capacity of wetlands also serve to allow wetlands within and

downstream of urban areas to counteract the increased rate of surface water runoff from

pavement and buildings. (EPA, Flood Protection, 2007)

2.6 Con

Since natural wetland systems are effective at improving water quality and preventing

floods, engineers and scientists construct artificial wetland systems that replicate the functions of

natural wetlands. CSW BMPs use natural processes involving wetland vegetation, soils and the

associated microbial life to improve water quality, support habitat life, increase biological

diversity, attenuate flooding and reduce peak discharges (Metropolitan Council, Constructed

Wetlands Stormwater Wetlands, 2001).

Constructed stormwater wetlands regulate stormwater runoff from a variety of both

impervious and vegetated sources ranging from roadways, parking lots, roofs, construction sites,

golf courses and lawns. CSWs help to intercept pollutants, such as nutrients, road salts, heavy

metals, petroleum, sediments and bacteria, from the stormwater runoff. The longer the contact

time between th

13

aims to create the longest possible flow path in order to maximize the contact of stormwater with

the CSW; this is achieved by providing long flow paths at shallow depths. The

length s,

lizing

stormwater

be delivered in a sheet flow to the remainder of the CSW. Sediment forebays ought to

ast 10% of the CSW volume. Gabions, riprap or berms are used to separate the

remove

e sediments. To allow for this, a concrete bottom is often installed to support this machinery.

avis, 1995)

s to

the surfaces of

of these paths can be increased by adding berms to form meandering channels. (Davi

1995)

Constructed stormwater wetland design also includes a sediment forebay which slows the

stormwater inflow and absorbs its force while reducing peak storm flow volumes and equa

flow to the CSW. The sediment forebay traps heavier sediment loads and prevents them from

entering the rest of the CSW. These heavier sediments, namely sands and gravels, contain a

large amount of the pollutants. Removing them in the forebay helps to reduce the buildup of

sediment in the rest of the CSW, thus extending its life. The forebay also allows for

to

encompass at le

forebay from the rest of the CSW. The forebay must have access for heavy equipment to

th

(D

2.7 Plantings

Dense vegetative growth aides sedimentation and provides sites for microorganism

growth within the CSW. A diverse community of wetland plants is less vulnerable than low

diversity communities to disease and animals. The most diverse and dense plant growth usually

occurs in shallower areas, and more efficient pollutant removal also occurs in these areas.

(Davis, 1995) Plant species should be selected based on how well the CSW site matches their

environmental requirements. Hydroperiod, light conditions, and depth ranges are some factor

be considered. It is also important to use plants which are native to the region in which the CSW

is built. (Metropolitan Council, Constructed Wetlands Stormwater Wetlands, 2001)

2.8 Pollutants

This section will discuss the pollutants evaluated in the present studys analysis.

14

2.8.1 Nitrogen

The most important forms of nitrogen found in CSWs are nitrogen gas (N2), nitrite (N

nitrate (

O2),

NO3-), ammonia (NH3), and ammonium (NH4+). The chemistry of nitrogen removal is

comple

re

it.

position

a

, 1995)

trification rates begin to drop at 6C and become repressed at 10C (Picard et al.,

2005).

its

ntration of nutrients in the plant tissue. The desirable traits of a plant

for nut

r phenomenon because a

majorit

x. CSWs chemically transform nitrogen between its inorganic and organic states through

various mechanisms: volatilization, ammonification, nitrification, nitrate-ammonification,

denitrification, N2 fixation, plant and microbial uptake, ammonia adsorption, organic nitrogen

burial and ANNAMOX (anaerobic ammonia oxidation). Some of these mechanisms require

energy and others release energy that is used by organisms. These nitrogen transformations a

required for CSW ecosystems to function efficiently, and most of these chemical changes are

controlled via the production of catalysts and enzymes by the organisms in which they benef

(Vymazal, 2007)

A significant portion of organic nitrogen is converted to ammonia through decom

and mineralization processes in the CSW. Ammonia is oxidized to nitrate by nitrifying bacteri

in the aerobic process of nitrification; these bacteria grow on wetland vegetation. (Davis

Denitrification converts nitrate into nitrogen gas with the aid of denitrifying bacteria; this gas is

then released into the atmosphere (DeBusk, 1999). Nitrification is inhibited in the colder

months; ni

Some nitrogen is taken up directly by wetland plants and becomes incorporated into the

plant tissue through nitrogen assimilation. This process converts inorganic nitrogen into organic

compounds which serve as the building blocks for cells and tissues. The two most commonly

used forms of nitrogen in assimilation are ammonia and nitrate. They are assimilated through the

roots and shoots of submerged plants. The rate of nutrient uptake by a plant is limited by

growth rate and the conce

rient assimilation include rapid growth, high tissue nutrient content and the ability to

accomplish a high standing crop. (Vymazal, 2007)

Constructed stormwater wetlands are affected by the seasonal cycles of ambient

temperatures and solar radiation. Nutrient uptake is a spring-summe

y of assimilation occurs during the growing season. The CSW nutrient cycle is

continuous as the plant biomass decomposes over the winter, thus releasing nitrogen back into

15

the CSW waters, where they again will be assimilated during the next growing season. (Picard e

al., 2005)

Numerous studies have been conducted to examine the nitrogen removal capabilities of

CSWs. Kadlec (1995) studied nitr

t

ogen removal in surface flow constructed wetlands treating

astewater. Nitrogen was present in various forms throughout the wetlands. Biota utilized both

um, while decomposition processes released organic nitrogen and ammonium

back in 0 g/m2

d

oval

ANZE

ighly portable element in CSWs, and it is involved in numerous

biologi d

d

wetland plants and therefore signifies a major link between organic and inorganic phosphorus

w

nitrate and ammoni

to the water. One turn-over of 3000 g/m2 of biomass at 3% nitrogen represented 9

of nitrogen transfer, which is considerable in comparison with most wastewater nitrogen

loadings. (Kadlec, 1995)

Reinhardt et al. (2006) examined nitrogen fluxes in a small CSW in Switzerland an

found the CSW removed 45 g/m2 of nitrogen per year, which corresponded to a nitrogen rem

efficiency of 27%. Denitrification supplied 94% of the nitrogen removal, while 6% of the

removed nitrogen built up in the sediments. (Reinhardt et al., 2006)

Birch et al. (2004) studied the efficiency of a CSW in removing contaminants from

stormwater in Sydney, Australia. Urban stormwater flowing into Port Jackson in Sydney was

highly contaminated with pollutant nutrients. A CSW treating this stormwater was studied

during rain events by collecting samples from both the inlet and outlet of the CSW. The mean

concentration of total nitrogen (TN) in the inflow to the CSW was 36 times greater than the

CC/ARMCANZ guideline values (0.1-0.5 mg/L N), and the average removal efficiency of

TN was 16%. (Birch et al., 2004)

2.8.2 Phosphorus

Phosphorus is a h

cal and soil-water interchanges. Dissolved phosphorus is present in both organic an

inorganic forms, and it is readily converted between the two. (Davis, 1995) Organic forms of

phosphorus are generally not biologically or chemically reactive in CSWs and are instead

removed when adsorbed by wetland soils. (DeBusk, 1999) Wetland soil is a major sink for

phosphorus, but removal decreases as adsorption sites become occupied. The length of this

removal period depends on the chemical adsorption capacity of the sediments. (Davis, 1995)

Orthophosphate is the only form of phosphorus thought to be used directly by algae an

16

cycling nic

en the plants die in the fall.

Becaus

rates

,

riations of

hosphorus within a cold climate subsurface flow constructed wetland, and the average annual

emoval rate was found to be 46%. Tonderski et al. (2005) modeled the impact of

CSWs

the

removal on a seasonal basis (McCarey et al.,

2004). ase

in CSWs (Vymazal, 2007). Organic phosphorus can also be broken down into inorga

phosphorus through the process of mineralization. This inorganic phosphorus can then be

removed through chemical and biological processes such as plant uptake. (DeBusk, 1999)

Wetland plants uptake soluble reactive phosphorus through leaves, roots and shoots and

convert it into tissue phosphorus. Soluble reactive phosphorus can also be absorbed by wetland

soils and sediments. There are various phosphorus transformations in CSWs: soil accretion,

adsorption, precipitation, plant/microbial uptake, fragmentation and leaching, mineralization, and

burial. (Vymazal, 2007)

Even though the seasonal uptake of phosphorus by plants can be considerable, the

phosphorus is generally recycled back into the CSW annually wh

e of this, long term phosphorus removal by CSWs is limited. (Davis, 1995) Similarly to

nitrogen removal, phosphorus removal in CSWs varies on a seasonal basis. Higher removal

are seen in the growing season while lower removal rates occur in the winter months. However

temperature affects phosphorus removal less than nitrogen removal because phosphorus removal

is dominated more so by sediment adsorption than biological processes. (Picard et al., 2005)

Several studies have examined phosphorus removal in CSWs (McCarey et al., 2004;

Tonderski et al., 2005; Birch et al., 2004). All studies have reported removal efficiencies

between 10 and 46%. McCarey et al. (2004) monitored the spatial and temporal va

p

phosphorus r

on phosphorus retention in southern Sweden and found that the CSWs functioned as sinks

for total phosphorus (TP). The CSWs removed 10 to 31% TP. As previously mentioned, Birch

et al. (2004) studied the phosphorus removal potential of a CSW in Sydney, Australia. The mean

concentration of TP decreased from 0.14 to 0.12 mg/L as the stormwater runoff traveled from

inlet to the outlet, corresponding to an overall reduction of 15%.

Mass balances throughout a year long study period on a subsurface CSW indicated a net

removal of phosphorus in all circumstances except for during the spring season. Its results

demonstrated significant variation in phosphorus

A CSW study in Sweden showed that during the warmest months, there was an incre

in outflow concentrations of phosphorus, suggesting that changes in the TP cycling within the

CSWs were what controlled phosphorus removal during warmer periods. It was hypothesized

17

that phosphorus release from both accumulating solids in the sediment and phytoplankton uptake

was responsible for the outflow concentration increases. (Tonderski et al., 2005)

2.8.3 Solids

Total suspended solids (TSS) are removed in a CSW primarily through sedime

filtration. TSS removal increases as the amount of vegetation and complexity of surfaces within

the CSW increase. Denser vegetative growth promotes longer detention times, which increases

the amount of sedimentation, and thus TSS removal. (Davis, 1995) Vegetation reduces the

turbulence and w

ntation and

ater velocity of the runoff. Sometimes particles flow into the plant stems and

aves, or they stick to the biofilm layers of the plants. Vegetation can shelter the particles from

d it is also possible for aggregates of the suspended solids to be formed through

floccul

wo

ally pass unaltered through CSWs.

(DeBus

ers

A majority of this chloride infiltrated into the wetland and moved laterally to the upland with

le

resuspension, an

ation within the CSW. (Braskerud, 2001)

Braskerud (2001) found that resuspension decreased 40% in four years and became

negligible in a five year old CSW. Birch et al. (2004) found the TSS removal efficiency of a

Sydney CSW to be between 9 and 46% for four high flow events. They also discovered that

significantly higher TSS concentrations were found in the effluent than in the influent during t

extremely high flow events. These two events had TSS removal efficiencies of -98% and -67%.

TSS removal is less efficient during extreme storm events because the retention time of the

particles within the CSW is diminished as resuspension dominates. (Birch et al., 2004)

Total dissolved solids (TDS) are a combination of both inorganic and organic

compounds. Some of these compounds can be biologically or chemically utilized in the CSW.

However, TDS are generally composed of unreactive dissolved compounds that are not removed

in CSWs. TDS are similar to chloride ions because both gener

k, 1999)

2.8.4 Chloride

Studies often show that chloride passes through CSWs unaltered (Carlisle and

Mulamoottil, 1991; Rea, 2004). The main source of chloride comes from road salt, which ent

the CSW in snowmelt runoff. Hayashi et al. (1998) found that snowmelt runoff transported

between 4 and 5 kg/yr of chloride from the upland to a prairie wetland in Saskatchewan, Canada.

18

shallow groundwater. The chloride then moved upward and accumulated near the surface while

water was removed via evapotranspiration. A portion of this chloride mixed w

ith snowmelt

runoff a nal

r.

ownward flow of groundwater to the deep aquifer, but for the most part the chloride

moved through the wetland unchanged. (Hayashi et al., 1998)

ave shown chloride removal within CSWs. Mitchell and Karathanasis

(1995)

es.

necessity for plant physiological processes like the water-

splittin et

t,

ts.

f

nd was again returned to the wetland. This chloride cycle was a continuous and seaso

process, and around 5 kg of chloride were cycled between the upland and wetland each yea

The cycle occurred within 5-6 m of the ground surface. A minor amount of chloride escaped this

cycle in a d

Some studies h

simulated CSWs in a greenhouse study. One CSW had surface flow, and another had

subsurface flow. In a 12 week period, 25% chloride removal was found in the surface flow

wetland. Chloride removal was not influenced by plant species or substrate type, and there was

no apparent time effect. It was theorized that this chloride removal came from plant uptake,

anion exchange within the substrate, and adsorption in the form of metal-chloride complex

No chloride removal was observed in the subsurface flow experiment. This was likely due to the

saturation of the substrate anion exchange capacity or by competition for metals by other ions,

yielding fewer metal-chloride complexes. (Mitchell and Karathanasis, 1995)

Xu et al. (2004) found that T. latifolia and P. australis both took up chloride ions in a

greenhouse study. Chloride is a

g step of photosynthesis, and this might be a reason for its uptake by some plants. (Xu

al., 2004)

2.9 Invasive Species

Roadways supply suitable conditions for the invasion and establishment of exotic species

in CSWs. Roads alter soil density, salt levels, heavy metal levels, temperature, light levels, dus

surface waters, runoff patterns, sedimentation, and nutrient levels in the roadside environmen

Roads also further the dispersal of exotic species through the altering of habitats, stressing o

native species and providing easier movement by wild or human vectors. (Trombulak and

Frissell, 2000) Road construction modifies soils and causes disturbances to flood frequencies.

This stresses the native plants, and they cannot fend off invasive species, making possible the

spread of exotic plants. (Cusic, 2001) These exotic plants often establish colonies along

19

roadsides or in disturbed habitats, and this causes major impacts on the biodiversity of a C

(Trombulak and Frissell, 2000).

Several studies have demonstrated how the salinity from road salts can decrease the

species diversity of a CSW. De-icing salts are generally composed of sodium chloride (NaCl),

but they can also be made of calcium

SW

chloride (CaCl2), potassium chloride (KCl) and magnesium

ant

y

in

ly salt-tolerant and is able to invade a colony of native

plants i

in northeastern Illinois. Marsalek

(2003) to a less

or

e

olonize both high

and low s

arsh

linities

chloride (MgCl2) (Trombulak and Frissell, 2000). Mature plants are generally more salt-toler

than seeds and seedlings, and some plant species are more resilient to salt than others. Road salt

has the capability of influencing the vegetative diversity of a freshwater CSW by substantiall

affecting seedling development and interspecific competitions. (Miklovic and Galatowitsch,

2005) Miklovic and Galatowitsch (2005) examined the effect of the addition of NaCl to a

greenhouse wetland microcosm. Eleven native plants were used in this microcosm. Five NaCl

treatments and two Typha angustifolia (cattail) treatments were assigned to the native plants

the microcosm. T. angustifolia is fair

n a CSW receiving high salt loads. Species diversity decreased in the NaCl treatments,

and it decreased more so in the NaCl and T. angustifolia treatments, suggesting that T.

angustifolia outcompeted the native species in the salt-laden environment. (Miklovic and

Galatowitsch, 2005) Panno et al. (1999) found similar results when T. angustifolia replaced the

native vegetation in a road salt laden fen-wetland complex

also described how road salt discharges caused another CSW ecosystem to shift

desirable species, Typha latifolia.

Phragmites australis is another undesirable salt-tolerant species. Disturbances along

roadways such as ditch digging, the application of de-icing salts, and runoff nitrogen input fav

the invasion of common reed colonies, such as P. australis, both along the roadways and in

CSWs. (Jodoin et al., 2008) Richburg et al. (2001) found that high salt concentrations from road

de-icing salts diminished the species diversity within a Massachusetts wetland. Many of th

native plants were less salt-tolerant than P. australis. P. australis was able to c

salt concentration areas within the wetland, and as a result the native plant colonie

diminished. (Richburg et al., 2001)

P. australis has a wide salinity tolerance and inhabits both freshwater and brackish m

environments. It has the ability to incorporate salts via ion accumulation, and it develops

osmotic regulatory pressure in its rhizomes. P. australis is able to reduce surface soil sa

20

by seizing salts in its belowground tissues. An effect of this is a higher capacity for ammon

adsorption in the soil. (Windham and Lathrop, Jr., 1999)

P. australis is considered to be a wetland invasive species because of its quick

population expansions over the past century and its ability to rapidly dominate marsh plant

communities throughout the United States. P. australis grows in dense patches, and its height,

stem density and detrital accumulation reduce the available light to the marsh surface soil, as

well as reduce the air te

ium

mperature. As a result, the germination and establishment of other plant

species as

ly

produc is

y

e

cies.

ed toxic

oxygen in

ts

competitor for this limiting nutrient because it is able to oxygenate its rhizosphere. Buried

may be inhibited. The low light levels resulting from the biomass accumulation in are

of P. australis can drastically delay the spring thawing of marsh substrates, which further

prevents the establishment of non-P. australis species. (Meyerson et al. 2000)

Meyerson et al. (2000) described how P. australis is easily dispersed in water and

generally settles disturbed sites. P. australis reproduces via a dynamic system of rhizomes and

stolons, and it forms dense monotypic communities (Ailstock et al., 2001). A root can on

e aerial stems, whereas rhizomes produce both aerial stems and underground roots. Th

gives an advantage to P. australis because it is able to utilize the nutrients stored in the

rootstocks, thus starting its growing season in the early spring. (Geller, 1972) P. australis

communities expand peripherally through lateral rhizome growth. The aerial stems formed b

the rhizome buds remaining from the prior years growth are used mainly for photosynthesis and

seed formation. At the end of the growing season, all of the aerial stems die and are restored th

following year through the growth of these pre-existing rhizome buds. The rapid growth rate of

P. australis via seeds, rhizomes and rooted shoots helps to make it an effective invasive spe

(Ailstock et al., 2001)

Windam and Lathrop, Jr. (1999) explained how P. australis uses a Venturi-enhanced

convective throughflow of gases to supply oxygen to its roots and to eliminate accumulat

gases. This enhances the oxygenation of below-ground tissues and increases the release of

into the rhizosphere. P. australis has low internal resistance to air flow suggesting aga

that it has a substantially high potential for root-zone oxygen release, which is consistent with i

ability to grow in deep waters and its deep rhizome and root penetration. (Tanner, 1996)

P. australis dominance might also be aided by the limitation of nitrogen. Under low

redox potentials, plants are restricted in their ability to uptake nitrogen. P. australis is a superior

21

organic nitrogen can be mineralized more quickly in this oxygenated environment, and as a

result, ammonium supply rates increase. Furthermore, slight increases in salinity levels inhibit

nitroge y

alt-

c

nd

.

s

than neighboring short grass communities in a tidal marsh in southern

New Je

lotype

a main reason for this rapid expansion in North America (Jodoin et al., 2008).

League et al. (2006) examined the differences between the native haplotype F and the

. australis in a brackish marsh in Delaware. Shoots from the exotic

strain e

s,

ify

n uptake, reduce the capacity of ammonium adsorption to soils, and limits productivit

due to the energy investments required to exclude salts. However, since P. australis is more s

tolerant than many native wetland plants, its nitrogen uptake is not limited. (Windham and

Lathrop, Jr., 1999) In a study of eight wetland plants in wetland mecocosms, Tanner (1996)

found that P. australis had the highest above-ground tissue concentrations of nitrogen. An

increase in the availability of nitrogen may be another mechanism by which P. australis

continues its successful invasion in wetland communities. (Windham and Lathrop, Jr., 1999)

Dr. Harsh Bais of the University of Delaware refers to P. australis as natural killers

(Wetlands Institute, 2008). Roots of P. australis produce 3,4,5-trihydroxybenzoic acid (galli

acid). This toxin targets tubulin, the structural protein that aids plant roots in maintaining their

cellular integrity. Gallic acid elevates levels of reactive oxygen species (ROS) in plant roots, a

ROS disrupts the root architecture of susceptible plants by damaging the microtubule assembly

Once this happens, susceptible plants die. (Rudrappa et al., 2007) This is one strategy that make

P. australis an effective invasive species.

Windham and Lathrop, Jr. (1999) found that P. australis plots had ten times the live

aboveground biomass

rsey. Interstitial water salinity was also 2% less in the P. australis plots (Windham and

Lathrop, Jr., 1999). In a similar study, Jodoin et al. (2008) reported that over the past fifty years,

the quantity and size of P. australis colonies have expanded substantially along roadsides in

Canada and the United States. The introduction of an exotic genotype of P. australis, hap

M, is thought to be

exotic haplotype M of P

merged from the rhizomes earlier than those from the native strain. Come March, there

were substantially more new shoots of the exotic strain when compared to those of the native

strain. By August, the exotic strain was 30% taller than the native strain, and it also contained

twice the amount of both the leaf and total biomass. The combined factors of greater biomas

longer rhizome internodes, and the earlier surfacing of new shoots from rhizomes help to just

22

the exotic strains advantage over the native strain as well as the means of its invasive nature.

(League et al., 2006)

Saltonsall (2002) found that the native haplotype of P. australis still remains in its

original range throughout North America. However, throughout this range there has been a rapid

expansion of the exotic haplotype M. I

t has replaced native types throughout New England, and

it has b

ductivity

nd Kadlec (2001) found that a greater species

diversity and species richness increased productivity in wetland mesocosms. Larger species

chness increased the amount of above-ground biomass. Each of the five plant species exerted

ifferent effects on above-ground biomass, the recovery of biomass after a disturbance, total

ry of respiration. (Engelhardt and Kadlec, 2001) Because

each in lhardt

s to

m

increased root

produc

een found in a test site in Camden, NJ, which is relatively close to Villanova, PA.

(Saltonsall, 2002)

2.10 Species Diversity

P. australis is the key species planted in CSWs in Europe because of its high pro

and its excellent nutrient removal capabilities. However, in the United States it poses a serious

weed risk. (Tanner, 1996) Preventing the invasion of P. australis is essential because of the

importance of species diversity. Engelhardt a

ri

d

ecosystem respiration and the recove

dividual species had unique and dominant effects on the wetland mesocosms, Enge

and Kadlec (2001) concluded that species diversity is important in order for different specie

fulfill different roles in an ecosystem.

Bouchard et al. (2007) found that an increase in species richness in a wetland mesocos

experiment enhanced belowground biomass and altered root patterns. The positive correlation

between species richness and belowground biomass was coupled with a more comprehensive

deployment of roots into varying soil layers in the highest diversity treatments. This suggested

that interactions among plant groups at higher diversity levels can impose soil resource

partitioning by inducing certain species to root at various and deeper depths. This

tion and increased rooting depth also served to decrease the amount of methane in the

wetland mesocosms. (Bouchard et al., 2007)

23

2.11 Phragmites australis Control

In order to promote species diversity within a CSW, P. australis invasion must be

controlled. Warren et al. (2001) found that mowing lowered the P. australis aboveground

produc

rren et al. (2001), these effects were

short te

in

of

ch is

d

l of the sections. In the first summer following herbicide treatment and cutting, no

plants g econd

pha

.

There were numerous P. australis reed removal effects. The microbial nitrogen demand

ould not compensate for the removal of nitrogen by plant uptake, and therefore an accumulation

tion and increased stem density, but it was ineffective for control. After an herbicide

treatment, the frequency of P. australis decreased and the total live cover was less than eight

percent, leaving mainly heavy litter and dense standing dead stems. After two growing seasons,

P. australis contributed three percent cover to the combined herbicide and mowing treatment

area. However, both of these values of P. australis doubled after four years. Hence, a single

treatment was ineffective for long term P. australis control. Recurring treatments are required to

adequately control the invasive ability of this reed species. (Warren et al., 2001)

Ailstock et al. (2001) demonstrated that a one time herbicide application or herbicide

followed by a burning drastically reduced the abundance of P. australis in nontidal wetlands.

These reductions were then followed by a regrowth of other species, which thereby increased the

species abundance and diversity. In accordance with Wa

rm, and after the third growing season, there was a significant expansion of P. australis

that was not killed in the initial herbicide application. Because of this, additional spot herbicide

applications are required to prevent the long term regrowth of P. australis, as well as to mainta

plant biodiversity. (Ailstock et al., 2001)

Findlay et al. (2003) removed P. australis with a Rodeo herbicide spraying at the end

the growing season followed by a cutting the following spring. They partitioned the CSW into

different sections for comparison before treatment began. One section contained Typha, whi

a common genus replaced by P. australis. One section contained P. australis as a reference an

another section was a P. australis removed area. The plants and biomass were collected and

sampled in al

rew in the treated site and a thick layer of plant litter covered the area. By the s

summer, the litter layer had disappeared, and by the third summer, a patchy regrowth of Ty

and P. australis covered half of the treatment area. Substantiating the findings of Warren et al

(2001) and Ailstock et al. (2001), control was effective in the short term but without continuous

treatment, P. australis grew back. (Findlay et al., 2003)

c

24

of ammonium occurred in the porewater that lasted at least two growing seasons. P. australis

ructure facilitates oxygen transport to the rhizosphere, and since microbial nitrogen demand

epends on the external oxygen supply, the killing of P. australis diminished the microbial

nitrogen demand, thereby increasing the ammonium content in the porewater. Since rhizosphere

oxidation by P. australis is a source of oxygen for nitrification, reed removal would cause a

decrease in nitrate, resulting in a decrease in denitrification. Another negative effect of the P.

australis reed removal was the reduction in nutrient sequestration in the plant biomass. (Findlay

et al., 2003)

Findlay et al. (2003) also found positive effects from the P. australis removal.

Originally, low diversity P. australis occupied the CSW. After reed removal, the species

richness of the CSW increased. When only P. a was present, there was an average of

three species per meter squared; after cutting, the regrowth contained an average of more than

seven species per meter squared. (Findlay et al., 2003)

st

d

ustralis

25

Chapter Three: Methodology

This chapter describes the protocol used in the collection and analysis of samples. The

ntation used in data and sample collection, sampling routine and schedule and

rocedures will be explained in detail.

3.1 Introduction

instrume

laboratory p

3.2 Sampling Sites

The Villanova University CSW is located in Villanova, PA; it borders County Line Road

and is near several academic and maintenance buildings (Figure 3.1). It receives stormwater

runoff from approximately 56.6 acres of campus, 57.2% of which are impervious surfaces

(Jones, 2008). There are three water quality sampling sites within the CSW: the inlet, the

sediment forebay, and the outlet (Figure 3.2). Flow is sampled at two inflow pipes (inlet) and

one outflow pipe (outlet).

Figure 3.1: Location of CSW at Villanova University (Rea, 2004; Stormwater Wetland Project Report, 2008; Woodruff, 2005)

26

1. Inlets

2. Sediment Forebay

3. Outlet

Figure 3.2: Sampling Site Locations within Villanova CSW

Inlet Main consists of a 42 inch pipe that transports flows from Mendel Hall, Tolentine

Hall, John Barry Hall and Falvey Library into the inlet of the Villanova CSW (Figure 3.3). Inlet

West contains a 48 inch pipe that transports flows from the Villanova University School of Law,

the law school parking lot, the nursing school and the West Campus apartments into the inlet of

the CSW, next to Inlet Main (Figure 3.3). While each inlet pipe was sampled individually for

flow, the water quality samples were taken just downstream of the entrance location as a

composite of the two inflows. The remainder of the watershed immediately adjacent to the CSW

enters the system via sheet flow and is not monitored.

The inlet is of significance because its layout changed throughout the study. In the

summer of 2007, construction began on the law school parking lot, located next to the inlet.

Throughout the fall and winter, the parking lot was excavated to allow for construction of the

new law school. Piles of soil became a constant sight in areas adjacent to the CSW. At the inlet

itself, numerous trees and foliage were removed. The grass on the hills leading down to the

CSW was also removed and a stone wall was constructed. Additionally, a flume was installed

in the summer of 2008. All in all, numerous changes occurred during construction that altered

27

the area around the inlet and may have impacted water quality sampling (e.g. erosion and

sedimentation controls, such as silt fences were utilized, although they were occasionally in

disrepair). However, the flow through the inlet pipes was not impacted by the construction as the

flow originated upstream of the construction.

Inlet Main

Inlet West

Figure 3.3: Inlet Main and Inlet West

The second sampling site in the Villanova CSW is the sediment forebay (Figures 3.2,

3.4). The sediment forebay is a pool of water which enables particles to settle out of the water

column. It was offset from the CSW in order to bypass high flows while allowing low flows to

enter the forebay. The offset design also serves to avoid constant turbulence and to prevent the

resuspension of particles. The sediment forebay measures 40 ft by 40 ft by 4 ft; it was originally

thought that the watershed was smaller. The sediment forebay was designed to hold 0.1 inches

of runoff from impervious surfaces and 0.05 inches of runoff from the entire watershed.

(Stormwater Wetland Project Report, 2008; Woodruff 2005) Unlike the inlets, the sediment

forebay does not consist of a pipe that conveys flow, and no flow was monitored. Water quality

samples were collected at the downstream end of the forebay.

28

Figure 3.4: Sediment Forebay

T-shaped weir

15 inch orifice and V-notch weir

Pressure Transducer

Figure 3.5: Outlet Structure

29

The third sampling site of the Villanova CSW is the outlet (Figure 3.2). The outlet

structure consists of a T-shaped weir, which controls the 25 and 50-year storms, and below the

T-shaped weir is a 15 inch orifice (Figure 3.5). A V-notch weir was installed in this orifice in

the fall of 2007 to measure low flows. The sides of the outlet structure each contain rectangular

slits that act as weirs as another control mechanism. The top of the outlet contains an iron grate,

which discharges the 100-year storm. A gabion was constructed in front of the outlet structure at

an elevation to pass the ten-year storm, and a smooth elevated weir was built at the end of the

gabion to allow flow to enter the outlet. Water quality samples were collected directly upstream

of the water flowing into the concrete outlet structure.

3.3 Instrumentation

Flow

The Sigma 950 is a portable flow meter that is self-contained (Figure 3.6) and measures

the average velocity of flow by using an area/velocity bubbler probe in order to measure the

velocity and depth of flow within the two inlet and outlet pipes. The area/velocity probe

contains a small air line that is attached to the Sigma 950. The 950 pumps air bubbles into this

air line and through the pipe, and it then measures the pressure of the air bubble at the release

point while calculating the depth of water from a calibration standard. The probe uses the

Doppler Effect to measure the velocity of the flowing pipe. The Sigma 950 releases a sound

wave from one end of the probe in order to measure the shift in frequency as the wave moves

away with the flow. This shift allows the Sigma 950 to determine the velocity of the flow. The

flow is calculated based on the current level of water and the continuity equation. (Hach, Sigma

950 Flow Meter, 2004) The Sigma 950 for Inlet Main is located in a metal cage behind the St.

Augustine Center and measures the flow at the upstream end of the pipe to avoid backwater

effects. The Sigma 950 for Inlet West is located in a metal lockbox at the inlet of the CSW and

the velocity and depth sensor is located about two feet upstream of the inlet. The Sigma 950 for

the outlet is located in a metal lockbox above the outlet structure, and the sensor is located

downstream of the outlet structure.

30

Figure 3.6: Sigma 950 Flow Meter

The outlet is also equipped with a pressure transducer (Figure 3.5). The pressure exerted

on a submerged object is the sum of the hydrostatic pressure from the depth of water and the

atmospheric pressure. The pressure transducer installed at the outlet is the PS9800 5PSIG, which

is able to measure depths of up to roughly ten feet. The transducers 4-20 mA signal can be read

directly by the Analog Input capabilities available on the outlets American Sigma 950 Flow

Meter. The pressure transducer was calibrated on a monthly basis by submerging it in various

known depths of water. Once the pressure transducer calibration was completed, the depth data

were logged at specified time intervals and then stored on the Sigma 950 for later recovery.

(VUSP Watersheds Laboratory, 2007)

The pressure transducer is used in conjunction with the 90 V-notch weir to calculate

flow during low flow periods at the outlet. The pressure transducer measures the depth upstream

of the weir. The geometry of the V-notch weir makes it capable of accurately measuring both

low and high flows, although it is only intended to measure low flows in this application. The

weir at the outlet (Figure 3.7) was machined from an aluminum plate according to ASTM

standards, and it was securely mounted to the 15 inch orifice of the outlet structure. (VUSP

Watersheds Laboratory, 2007)

31

Figure 3.7: View of V-notch Weir from within the Outlet Structure

The general equation for flow over a V-notch weir is:

21

2

1

*2

tan*2**158

HgCQ d

= )1.3(

Where: Q = flow rate (ft3/s)

g = gravity (ft/s2)

Cd = is the coefficient of discharge (varies)

= angle of V-notch (varies) H = head on weir (ft)

The angle of the V-notch weir ( ) is 90. (VUSP Watersheds Laboratory, 2007)

Precipitation

An external tipping bucket rain gauge (American Sigma Model 2149) is connected to

the Sigma 950 at Inlet West (Figure 3.8). It provides a dry contact closure to the flow meter

(Hach Sigma 950 Flow Meter Instruction Manual, 2004). When 0.04 inches of rain occur in a 25

32

minute time period, the rain gauge signals the Inlet West Sigma 950 that a storm event is

happening. When this happens, the Sigma 950 triggers the Inlet West Sigma 900, an

autosampler, to begin collecting water quality samples.

Figure 3.8: American Sigma Model 2149 Rain Gauge

Water Quality

The Sigma 900 can be programmed to take samples at various time intervals (Figure 3.9).

There are three Sigma 900s at the Villanova CSW which are located at the three water quality

sampling sites: inlet (a composite just downstream of the headwall where Inlet Main and Inlet

West enter the CSW), sediment forebay, and the outlet. When the Sigma 900 at Inlet West is

triggered by the Inlet West Sigma 950, it in turn activates the Sigma 900s at the sediment forebay

and outlet. A four-way splitter is used to directly connect all of the Sigma 900s to the Inlet West

Sigma 950 (VUSP, QA-QC Project Plan, 2008). During the fall of 2007 and winter of 2008, the

Sigma 900s at the sediment forebay and outlet had to be manually triggered because the wiring

connecting them to the inlet was not working. These data lines were repaired on February 25,

2008.

33

Figure 3.9: Sigma 900 Automated Sampler

The Sigma 900s at the inlet, sediment forebay and outlet all had twelve (Model AM.S16)

350 mL sample bottles (Figure 3.10). The sampling regime spanned 36 time intervals. At each

time interval, one sample was taken, and three samples were taken per sample bottle. A

composite of three samples per bottle yielded 12 total composite samples for the sampling

period. Each bottle held three 100 mL samples, yielding 12 total samples of 300 mL each. The

time intervals for these 36 intervals are found in Appendix A. The intervals at the inlet were

shorter than those at the sediment forebay and outlet, ending at hour 36. The interval lengths of

the sediment forebay and outlet were longer than those at the inlet because it took longer for flow

to reach them; past studies (Rea, 2004; Woodruff, 2005) did not always capture the tail of the

storm hydrograph, so exaggerated sampling periods at the sediment forebay and outlet were used

to avoid this problem. Similarly, the sampling period at the outlet (87 hours) was longer than

that at the forebay (82 hours) because it took the longest for flow to reach the outlet.

34

Figure 3.10: Bottle Setup within the Sigma 900

3.4 Sampling Routine

This study consisted of research from both baseflow and storm events. Baseflow was

defined as the flow occurring within the CSW a minimum of 72 hours after a precipitation event.

A storm event was defined as when 0.04 inches of rain occurred in a 25 minute time period. The

rain gauge determined if these parameters were met.

The sampling schedule was divided into four periods: fall (September-November),

winter (December-February), spring (March-May), and summer (June-August). The goal was to

collect three storm events and three baseflow events in each sampling period, although flow was

monitored continuously. Due to instrument malfunction and the lack of precipitation events, this

goal was not always met. The data from each period are compared with each other in order to

analyze the efficiency of the CSW in removing nutrients throughout the year.

3.5 Collection and Analysis Protocol

The samples for the storm events were collected by the Sigma 900s at the inlet, sediment

forebay and outlet. The samples for the baseflow events were collected in person with grab

sample bottles (Nalgene 250 mL). Three grab samples were taken at each of the three water

quality sampling sites. After the samples were taken, they were immediately taken to the

Villanova University Water Resources Laboratory to be analyzed. Both baseflow samples and

storm event water quality samples were tested for the same parameters: total nitrogen, total

phosphorus, total orthophosphate, total chloride, total suspended solids, and total dissolved

35

solids. All collection techniques and laboratory analysis complied with recommended practices

by the manufacturer and an EPA approved QAPP.

3.6 Total Nitrogen and Total Phosphorus

The Hach DR/4000 Spectrophotometer was used to conduct the total nitrogen and total

phosphorus tests. The spectrophotometer measures the amount of light absorbed at specific

wavelengths in order to determine the concentration of a sample. The measured absorbance can

then be related to different chemical parameters. (Dukart, Total P Total N, 2007)

Accurate sample volumes were necessary for determining the correct concentration

samples. TenSette Pipets were therefore used to precisely measure sample volumes. Models

19700-01 (one mL max) and 19700-10 (ten mL max) pipets were used depending on the sample

required. In order to prevent cross-contamination, the tip was changed between each sample.

(Dukart, Total P Total N, 2007)

The Hach DR/4000 uses one inch square glass sample cells. The suggested cleaning and

handling procedures were strictly followed in order to prevent interference from the glassware.

Finger contact was avoided with the clear sides of the cells. The cells were oriented in the one

inch square cell adapter within the sample module, so that the fill marks were facing the user and

the clear sides were facing the lamp. The cells were wiped with a cloth to remove smudges and

fingerprints. The total nitrogen and total phosphorus spectrophotometric analyses were done in

manufacturer prepared digestion vials. The vials were held by the plastic caps in order to avoid

touching the glass vials. The glass vials were again wiped with a cloth before being placed in the

spectrophotometer. After the analysis, the vials were immediately emptied into specified

hazardous waste containers because they were not reusable and were disposed of as described in

the products Material Safety Data Sheet. (Dukart, Total P Total N, 2007)

The total nitrogen and total phosphorous tests require that the samples go through a

digestion period at certain temperatures for 30 minutes (105 C and 150 C, respectively). The Hach COD Reactor Model 45600 was used to warm the samples for the required time periods. It

can hold up to twenty-five 16x100 mm vials, and it has the ability to sustain temperatures up to

150 C. The COD Reactor Model has two modes: 150 C mode and an adjustable temperature

mode. (Dukart, Total P Total N, 2007)

36

3.7 Total Orthophosphate

The Hach DR/4000 Spectrophotometer was used to test total orthophosphate until

January 2008. The total orthophosphate test was carried out in a similar fashion as the total

nitrogen and total phosphorus tests. In January 2008, total orthophosphate began being tested

with Systea technology using EasyChem methodology. In this method, the aqueous sample

containing orthophosphate was mixed with sulfuric acid, ammonium molybdate and antimony

potassium tartrate to form antimony-1, 2-phosphorous molybdenum acid. Then, this complex

was reduced by ascorbic acid to form a blue heteropoly acid (molybdenum blue). The

absorbance of the formed blue complex was measured at 660 or 880 nm, and it was proportional

to the concentration of orthophosphate. (Systea Scientific, Ortho-Phosphate, 2006)

3.8 Total Chloride

Chloride was tested with the High Pressure Liquid Chromatograph (HPLC) until January

2008. The HPLC consists of the following components: a Waters Model 626 HPLC Pump with

IonPac ASII-HC Anion-Exchange Column, a Waters Model 431 Conductivity Detector, a

Waters Model 600s Controller, a Waters Model 717plus Autosampler, a Dionex AMMS III

Eluent Suppressor, Galaxie Chromatography Data System Version 1.7.4.5, IonPac ATC-3 Trap

Column 9x24mm, AG11-HC Guard Column, 4x50mm, and IonPac ASH11-HC Analytical

Column, 4x250mm. (Salas-de la Cruz, 2007)

The HPLC injected small amounts of sample into an anion exchange column that

separated out the present anions. After being separated, the anions were read by a conductivity

detector. The measured conductivities were then plotted and computer software integrated the

area underneath the peaks for each individual anion. The area underneath the chloride peak was

then related back to the calibration standard in order to determine the concentration of chloride in

each sample. (Rea, 2004)

In January 2008, chloride began being tested with Systea. In EasyChem methodology, a thiocyanate ion was liberated from mercuric thiocyanate through the formation of soluble

mercuric chloride. In the presence of a ferric ion, free thiocyanate ion forms a highly colored

ferric complex. The intensity of this complex was measured at 480 nm, and this intensity was

proportional to the chloride concentration. (Systea Scientific, Chloride, 2006)

37

3.9 Total Suspended Solids/Total Dissolved Solids

The term total solids refers to the material residue that is left in a container after a

sample is evaporated and dried in an oven at a defined temperature. Total solids include both

total suspended solids, which are the portion of total solids retained by a filter, and total

dissolved solids, the portion that passes through the filter in water. (Dukart, Total

Suspended/Total Solid/Metals, 2007)

Accurate sample volumes were of extreme importance in determining the correct

concentration of the sample. Each vacuum flask was weighed empty and then reweighed with

the sample. The weight of the empty flask was subtracted from the weight of the flask plus

sample in order to calculate the exact volume passed through the filter. Also, each filter was

weighed both prior to and after filtration/drying in order to determine the mass of suspended

solids. Similarly, each evaporating dish was weighed both prior to and after filtration/drying in

order to determine the mass of the dissolved solids. The concentration of the

suspended/dissolved matter could then be calculated. (Dukart, Total Suspended/Total

Solid/Metals, 2007)

The solid filter papers and the displaced liquid were dried in dishes in ovens set at

approximately 100 C and 250 C, respectively, for at least one hour, or until dry. Desiccators were used to cool the samples without allowing moisture to permeate. (Dukart, Total

Suspended/Total Solid/Metals, 2007)

3.10 Pollutant Concentrations and Detection Limits

The water quality tests used have detection limits for pollutant concentrations. The Hach

total nitrogen test has a lower detection limit of 1.7 mg/L (Hach, 2003); those non-detected

samples falling below this range were given the value of 0.85 mg/L, which was half of the

detection limit. The Hach total phosphorus test has a lower detection limit of 0.06 mg/L (Hach,

2003); those non-detected samples falling below this range were given the value of 0.03 mg/L,

half of the detection limit. The Systea total orthophosphate test has a lower detection limit of

0.01 mg/L (Dukart, 2008); those non-detected samples falling below this range were assigned the

value of 0.005 mg/L. The Systea total chloride test has a lower detection limit of 0.5 mg/L

(Dukart, 2008); no samples fell below this limit. When the calculated total suspended solids and

total dissolved solids values were negative, these samples were assigned the value of 0. Some

38

samples had true total suspended solids values of 0: 10/2/07:WT-BF-I1, 11/6/07:WT-OT-05,

11/15/07:WT-OT-05, WT-OT-06, 1/29/08: WT-OT-04, 4/3/08:WT-IN-05, WT-IN-07,

7/17/08:WT-BF-O1, 7/23/08:WT-OT-08, WT-OT-10, and 8/19/08:WT-BF-O1 (Appendix B).

All storm event and baseflow event pollutant concentrations (mg/L) are found in Appendix B.

Values in bold-faced font are those below the detection limits.

3.11 Data Analysis

Water quality parameters were analyzed in the laboratory and pollutant concentrations

were typically recorded in mg/L. It is also beneficial to look at the pollutant transport by the

mass loading in and out of the Villanova CSW; the mass (M) was calculated using:

M CQ t= (3.2) where, C is concentration, Q is the volumetric flow rate, and t is the time interval. During

storm events, the time interval was five minutes because this was how often the flow rate was

measured by the Sigma 950s. During baseflow events, the average concentration of samples was

assumed representative of the season, the flow was that measured by the respective site Sigma

950 at the time of sampling, and the time interval was three months, representing an entire

sampling season.

Unlike the flow data, water quality samples were not collected every five minutes. In

order to estimate pollutant concentrations and loadings in five minute intervals, a linear

interpolation was performed in between storm sample times using Microsoft Excel.

Interpolating might not characterize random fluctuations, but it does give a good representation

of the total quantity of pollutants moving through the CSW during a storm event (Rea, 2004).

The percent removal of pollutants was calculated using:

% removal= Min-Mout* 100 (3.3)Min

A negative percent removal signifies that there was pollutant loading within the CSW, rather

than removal from the inlet to the outlet. (Wadzuk, 2008)

The Event Mean Concentration (EMC) is a flow weighted average concentration and was

used in the analysis of storm events. The EMC is the total mass (summing the interpolated

incremental masses) divided by the sum of the total flow volume multiplied by the time interval:

39

M

EMCQ t

= (3.4)

The EMC values were typically reported in mg/L. The percent reduction of pollutant EMC was

calculated using:

% reduction= EMC * 100 EMCin (3.5)

where EMC is the change in the EMC values between the inlet and the outlet

(EMC=EMCinlet- EMCoutlet). As the flow (Q) increases, the EMC decreases, and vice versa.

3.12 Plot Study

The location of the plot study was downstream of the sediment forebay and upstream of

the outlet (Figure 3.11). This location was chosen because it is located in the periphery of the

CSW. The periphery is more easily controlled by the glyphosate sprayings, so Phragmites

invasion poses less of a threat. The elevation of the CSW in this area decreases from upstream to

downstream, so water flows through the plots towards the outlet. A baseflow is also present,

which is essential for groundwater sampling. This area of the CSW is also more exposed to the

sun during the winter, so freezing is less of an issue.

Figure 3.11: Location of Plots (Pre-Study)

40

The plots were cleared over a three day period at the end of April 2008. Pitchforks, rakes

and spades were used to loosen up the wetland soil, so that Phragmites rhizomes could be

removed (Figure 3.12). The water was opaque and knee deep, so it was nearly impossible to

remove all of the rhizomes, but a good portion were taken up from the CSW (Figure 3.13).

Figure 3.12: Clearing of the Plots

Figure 3.13: Removed Phragmites Rhizomes

41

A

B

C

Figure 3.14: Cleared Plots

The cleared plots were sectioned off with stakes and rope into six foot by six foot

squares. Two six inch Model 601 Standpipe Piezometers were placed in each plot. Attached to

each piezometer was a 30 inch long, three-quarter inch diameter Schedule 40 PVC pipe. One

piezometer was placed in the upstream end of each plot (inlet), and one piezometer was placed in

the downstream end of each plot (outlet). The inlet piezometer was positioned so that its water

level was higher than that of the outlet piezometer. This was to assure that the groundwater

samples collected flowed through each plot from its inlet to its outlet.

In total, there were four plots. Three of these plots were cleared out in April: control,

sweet flag, and cattail. Because of spatial constraints, these plots were positioned in series

(Figure 3.14). The control plot (Figure 3.14, A) was located in the most upstream position,

nearest to the sediment forebay. It remained clear of plants and was composed of native wetland

soil. The sweet flag (Acorus calamus) plot (Figure 3.14, B) was downstream of the control plot,

and the cattail (Typha latifolia) plot (Figure 3.14, C) was downstream of the sweet flag plot. The

sweet flag plot was positioned in shallower water than the cattail plot because sweet flags

survive better at these depths (Sweet Flag, 2008). The fourth plot, Phragmites, was downstream

of the cattail plot, in the deepest water. Sweet flag reaches an average height of 1-4 feet

(Connecticut Botanical Society, 2008), cattail grows up to 5-10 feet in height (Typha latifolia,

2008), and Phragmites grows up to 12 feet tall (Wisconsin Department of Natural Resources,

2008). Their maximum heights were in accordance with their plot depths. The Phragmites plot

42

was offset from the other three plots to help prevent invasion. A patch of existing Phragmites

was sectioned off (Figure 3.15), and the length of the Phragmites plot from its inlet to its outlet

moved away from the periphery of the CSW because the elevation decreased in this direction,

and more importantly, the water flow followed this course. As a precautionary measure, the Ju

17, 2008 glyphosate spraying was not conducted in the Phragmites plot.

ne

Figure 3.15: Phragmites Plot

May of 2008, plugs of sweet flags and cattails were planted in pots. They were

fertilize g

t in the

(Picture taken on 2008) August 7,

In

d and watered until they became tall enough to be planted in the CSW without bein

submersed. On July 1, 2008, 50 sweet flags and 45 cattails were planted. At this time,

Phragmites and other foliage had grown in densely in areas surrounding the plots, but no

plots themselves. This is evidenced by the control plot which was free of plants, and more

importantly Phragmites (Figure 3.16).

43

Figure 3.16: Control Plot (Picture taken on August 7, 2008)

Most of the sweet flag and cattail plugs reached the surface of the CSW water, and some of them

broke the waters surface. The sweet flag plot (Figure 3.17) and the cattail plot (Figure 3.18)

both grew in biomass during the sampling period of July and August 2008.

Figure 3.17: Sweet Flag Plot (Picture taken on August 7, 2008)

44

Figure 3.18: Cattail Plot (Picture taken on August 7, 2008)

The four plots were sampled on three dates in July and August 2008. Two surface

samples and two groundwater samples were taken from each plot; one surface and one

groundwater sample were taken from the inlet of each plot, and one surface and one groundwater

sample were taken from the outlet of each plot. Surface and groundwater samples were collected

in 50 mL polyethylene bottles. Groundwater samples were taken with half inch diameter, 36

inch long poly weighted bailers. The inlet and outlet surface water samples were taken at the

same time, and the inlet and outlet groundwater samples were taken at the same time in each

plot. It was assumed that the two surface and two groundwater samples were of the same

population and were representative of the baseflow.

The surface and groundwater samples were immediately taken to and tested in the

Villanova University Water Resources Laboratory. The samples were tested for total nitrogen,

total phosphorus, total orthophosphate and total chloride. The same lab testing protocol as

described in Sections 3.6-3.9 was used. Total suspended and dissolved solids were not tested

because it was thought that the sweet flag and cattail plots would not yet be dense enough to

allow for sufficient removal.

45

Chapter Four: Storm Events

4.1 Introduction

This chapter will present and discuss the results from the storm events in the forms of

EMCs, loadings, percent reductions and percent removals. In addition, storm event data are

presented in a variety of pollutographs (found in Appendices C-V). The storm event

concentration pollutographs plot the concentration of each pollutant against t/(t rain event); t/(t

rain event) is the time the sample was taken divided by the time of the total rain event

(Appendices C-F). This was used to non-dimensionalize time, so all of the storms could be

compared efficiently. Four different mass loading pollutographs are used. One set of mass

loading pollutographs plot the loading of the pollutants throughout the sampling period (M)

against t/(t rain event) (Appendices G-J). The second set of mass loading pollutographs plot the

individual loadings at each of the five minute intervals divided by the total loading of the

sampling period (M/(M total)) against t/(t rain event) (Appendices K-N). The third set of mass

loading pollutographs plot the sum of the loading throughout the sampling period (M) against

t/(t sample length) (Appendices O-R); t/t(sample length) is the time of the sample divided by the

time of the total sampling period. Lastly, the fourth set of mass loading pollutographs plot the

sum of the loading at each of the five minute intervals divided by the total sum of the loading

from the entire sampling period (M/(M total)) against t/(t sample length) (Appendices S-V).

Each nutrient will be discussed separately. Individual storm events will be the main focus, but

seasonal storm summaries will also be touched upon.

Thirteen storm events were sampled between October 2007 and July 2008. These storms

ranged in size from 0.17 inches to 3.03 inches and in length from 3.8 hours to 65.9 hours (Table

4.1). Storm length was defined as the time from the beginning of precipitation to the last point of

precipitation before the start of a minimal 24 hour dry period. A new storm occurred after at

least 24 hours of no precipitation. When a new storm occurred during the extent of sampling,

this was classified as a double peaking storm event.

46

Table 4.1: Summary of Rainfall and Storm Length

The total rainfall amount and duration is given. If the storm was double peaking (i.e. a minimum of 24 hours between rainfall events) the amount and duration is given, which is in addition to the initial rainfall amount and duration.

Storm Date

Antecedent Dry Time

(hr) Rainfall (in) Storm

Length (hr)

Dry Time Between Initial and

Double Peaking

Storms (hr)

Double Peaking Storm

Rainfall (in)

Double Peaking Storm

Length (hr) 9-Oct-07 88.75 3.03 58 6-Nov-07 228.5 0.22 8.6

15-Nov-07 24.92 0.63 58 29-Jan-08 264.17 0.25 18.8 25.2 1.67 11.4 13-Feb-08 134.75 2.44 15.8 26-Feb-08 24.83