Turning problems into assets: protecting coastal resources with

constructed wetlands

Prof. Ron CarrollAssoc. DeanDirector-Science, River Basin CenterOdum School of EcologyUniversity of Georgia-Athens

Principal Collaborators

• Laurie Fowler: international water law and policy, UGA

• Prof. David Gattie: Environmental Engineering, UGA

• Dr. Dianne Sanzone: Research Head, Energy and Environment, Batelle Labs

• Prof. Manuel Spinola: Ecologist, National Univ. of Costa Rica

•Prof. William Tolner: Environmental Engineering, UGA

Problem Statement

The coastal zone is at the receiving end of excess nitrogen and phosphorus causing fish kills and human health risk from…

• blooms of toxic algae

• dead zones due to depleted oxygen

The sources of these excess nutrients are storm water run off, sewage and septic systems, irrigation with fertilizers, all of which also contaminate the coastal zone with

• pathogens• pesticides• other toxic chemicals

Due to high nitrogen and phosphorus

…in wastewater from sewage, septic systems, livestock , and fertilizer run off with irrigation

“Dead zones” shown in red are a worldwide problem, especially along densely populated coastal zones

Coastal pollution from these non-point sources will likely get worse in the U.S. because more than half the nation’s population lives in coastal counties and these counties generally experience the highest growth rates.

We need a better solution…..

According to the American Society of Civil Engineers (2009) our wastewater treatment systems should receive a grade no better than D-.

“Many systems have reached the end of their useful design lives. Older systems are plagued by chronic overflows during major rainstorms ….and are bringing about the discharge of raw sewage into U.S. surface waters.”

To be successful the “solution” must be…

• broadly effective at meeting water quality standards

• affordable and cost-effective to build and manage

• resilient to environmental change

To be successful the “solution” must be…

• adaptable to new conditions

• scalable to meet demands from growing populations

• accepted by the community

Continued

Constructed treatment wetlands meet these

conditions

How they work: the surface flow design

Shallow zone Deep pools

Constructed wetlands with alternating shallow aerobic and deep anaerobic cells and sized properly….

• reduce N and P below TMDL standards for swimmable streams• increase dissolved oxygen and greatly decrease organic carbon• eliminate pathogenic bacteria and viruses

Constructed wetlands are often seen as a community asset

For example, the constructed wetlands of Clayton County, Georgia are listed among the top five birding spots in the mid-Atlantic

Attractive flowering plants can be used to increase the aesthetics of the wetland

Overview of Panhandle Treatment Wetlands in Jonesboro GA. Our principal research site.

Panhandle wetlands consist of two sequences of 8 treatment cells and one sequence of 6 cells. Each cell is about 15m wide by 30m long and divided into two deep pool areas, separated by a shallow area with dense cattails.

The design allows a comparison of treatment effectiveness along a transect.

Jenny Pahl at first treatment cell. Complete coverage by duckweed indicates high nitrogen levels…but no mosquitoes

Duckweed benefits

• accumulates heavy metals• stores nitrogen (as protein)• fast growth (doubling time in days)• metabolites strongly inhibit mosquito larval development

Note the very large number of baby duckweed waiting for new space.

By cell 3 or 4 nitrate nitrogen, ammonia N and phosphorus are at or below TMDL limits for swimmable streams

N-fixing Azolla (red) in bottom pondindicates low levels of effluent nitrogen

Pathogenic, disease causing, bacteria and viruses are eliminated when the flow rate through the wetland is greater than three days. Generally, flow rates are much longer in constructed wetlands.

Pseudomonas auruginosa,a human respiratory pathogen sometimes foundIn wetlands.

Cañas wetland project

A developing country feasibility study

Cañas, Costa Rica, Project Teams

University of Georgia • Two ecology faculty plus students• Two environmental engineering faculty plus students• Two environmental design faculty plus students

EARTH university, Costa Rica• Two environmental sciences faculty plus students

National University of Costa Rica• Two conservation ecologists plus students

Cañas, Costa Rica, is a small town representative of other towns in the seasonally dry Pacific side of Central America.

Like all towns in this region, waste water is poorly treated, if at all.

The Cañas River runs through the town and empties its polluted waters into the head of the Gulf of Nicoya, a major domestic and export fisheries resource.

We have initiated a feasibility study of low cost options for cleaning and reusing Cañas waste water while producing value-added market assets.

These assets include

• Methane from anaerobic waste stabilization ponds

• Biomass stock for renewable energy (ethanol or methane) from constructed wetlands.

Waste stabilization (or oxidation) lagoons are the only sewage treatment facilities

Drainage ditch empties into the Cañas River

Circle encompasses area for constructed wetland. Cañas river is to the right.

Downstream tilapia farm. Nutrient rich effluent also contains male hormone ( synthetic androgen).

The large amount of biomass produced in constructed wetlands is a source of renewable energy.

Cattails and ethanol

Cattails play an important functional role in contributing to restoration of water quality by taking up N and P and providing surface area for microbial degradation of organic carbon and destruction of pathogens.

But, because their growth is so prolific, they must be periodically cut or burned to maintain flow and prevent stagnant areas that would breed mosquitoes.

We propose harvesting cattails to meet management objectives and, importantly, to produce significant revenue.

To accomplish this, the wetlands must be designed to allow harvesting without disrupting their function.

Parallel wetlands allow one to be drained and harvested while the other continues to function.

Our constructed wetland design for the Sewanee Utility District on the Cumberland Plateau, Tennessee. Similar parallel wetlands would be designed for the Cañas project.

To get a sense of the revenue potential from harvesting cattails and fermenting them into ethanol, we can make a comparison to average ethanol yields from Iowa corn.

Ethanol from Iowa corn100 acres yields 32,364 gal.*

* Must add fertilizer, pesticides and fossil fuel

Ethanol from southeastern cattails in constructed wetlands….100 acres yields approximately 102,287 gal., three times the yield of Iowa corn.*

* Without fertilizer, pesticides or fossil fuel

At $2.40 per gallon (20ll market price), 100 acres of constructed wetland cattails in the southeastern U.S.

produces $245,487 gross revenue.

THE TAKE HOME MESSAGES…..

WITH THE RIGHT DESIGN AND MANAGEMENT, CONSTRUCTED WETLANDS….

• ARE BROADLY EFFECTIVE AT REMOVING EXCESS NUTRIENTS, AS MUCH AS HALF TON OF NITROGEN

• AND DESTROYING PATHOGENS, PHARMACEUTICALS, AND MANY TOXIC CHEMICALS

• RESTORE OXYGEN AND REDUCE ORGANIC MATTER IN THE TREATED WASTE WATER

• DO NOT CREATE MOSQUITO PROBLEMS

• ARE SEEN AS AN AMMENITY BY THE COMMUNITY

• ARE RELATIVELY AFFORDABLE AND EASY TO MANAGE

• CAN PRODUCE SIGNIFICANT REVENUE FROM ETHANOL AND SOMETIMES FROM METHANE

Constructed wetlands (con’t)

THROUGH THEIR EFFECTIVE IMPROVEMENT OF WATER QUALITY, CONSTRUCTED WETLANDS CAN PROVIDE SIGNIFICANT PROTECTION OF COASTAL WATERS.

THE STRONG ASSETS THAT ARE GENERATED THROUGH COMMUNITY SUPPORT AND BIOMASS RENEWABLE ENERGY HELP ENSURE THE LONG TERM VIABILITY OF THE WETLANDS AND THEIR PROTECTIVE ROLE.