urban landscape irrigation with recycled wastewater: water quality and salinity issues yaling qian...

Urban Landscape Irrigation with Recycled Urban Landscape Irrigation with Recycled Wastewater: Wastewater:

Water Quality and Salinity IssuesWater Quality and Salinity Issues

Yaling Qian

Colorado State University

Water ReuseWater Reuse

In dry and highly populated In dry and highly populated metropolitan areas, where water is a metropolitan areas, where water is a limited natural resource, water reuse limited natural resource, water reuse is a viable means of coping with is a viable means of coping with potable water shortages. potable water shortages.

Without doubt, water reuse for Without doubt, water reuse for landscape irrigation will increase in landscape irrigation will increase in the future.the future.

Benefits of Recycle Water Benefits of Recycle Water IrrigationIrrigation

Water conservation;Water conservation; Always available;Always available; Water reclamation;Water reclamation; Nutrient recycling.Nutrient recycling.

Water Source for Golf Courses in Water Source for Golf Courses in Colorado - Colorado - In 2000In 2000

Potable Water 11%

Well Water 18%

Reclaimed Wastewater

10%

Surface Water 61%

Using recycled wastewater for landscape irrigation in Colorado Using recycled wastewater for landscape irrigation in Colorado started in the 1960’s to irrigate golf courses.started in the 1960’s to irrigate golf courses.

Water Source for Golf Course in Water Source for Golf Course in Colorado: Colorado: In 2002In 2002

Potable Water 12%

Well Water 16%

Recycled Wastewater

20%

Surface Water 52%

Water reuse practice has increased dramatically recently.Water reuse practice has increased dramatically recently.

Successful Recycled Wastewater Reuse CasesSuccessful Recycled Wastewater Reuse Cases

Olympic Club Castle Pine International

ChallengesChallenges

Sodicity and salinity problems;Sodicity and salinity problems;

Residential use of water typically adds about 200-400 Residential use of water typically adds about 200-400

mg/L of dissolved salts. Those salts have relatively high mg/L of dissolved salts. Those salts have relatively high

Na content that remain after wastewater treatment. Na content that remain after wastewater treatment. Nutrient issues;Nutrient issues; Groundwater quality.Groundwater quality.

ParameterParameter UnitUnit Value Value

Salt loadSalt load

Total dissolved salts (TDS)Total dissolved salts (TDS) ppm or mg/Lppm or mg/L 540540 0.448 lb/100 gal0.448 lb/100 gal

Electrical conductivity (EC)Electrical conductivity (EC) dS/m or mmho/cmdS/m or mmho/cm 0.840.84

SodiumSodium ppm or mg/Lppm or mg/L 9999

CalciumCalcium ppm or mg/Lppm or mg/L 6161

MagnesiumMagnesium ppm or mg/Lppm or mg/L 1515

Sodium adsorption ratioSodium adsorption ratio 3.13.1

Adjusted SARAdjusted SAR 5.05.0

BicarbonateBicarbonate ppm or mg/Lppm or mg/L 112112

ChlorideChloride ppm or mg/Lppm or mg/L 9595

BoronBoron

NitrogenNitrogen

ppm or mg/Lppm or mg/L

ppm or mg/Lppm or mg/L

0.230.23

10.310.3

PhosphorusPhosphorus ppm or mg/Lppm or mg/L 0.80.8

Water QualityWater Quality

Effects of salinity on landscape plantsEffects of salinity on landscape plants

Physiological drought:Physiological drought:

PPlants cannot take up enough water due lants cannot take up enough water due to salts.to salts.

Turf Injury Turf Injury

Salinity caution levels in irrigation water: Salinity caution levels in irrigation water:

EC > 0.75 mmho/cm EC > 0.75 mmho/cm

or or

TDS > 500 ppm.TDS > 500 ppm.

Turf Injury Turf Injury Salinity problems are functions of:Salinity problems are functions of: soil type, soil type, management, management, shallow water table will reduce shallow water table will reduce

leaching and introduce salts to the leaching and introduce salts to the root zone,root zone,

salinity of irrigation water.salinity of irrigation water.

Susceptible sites for salt accumulation: Shallow water table,High clay content,Poorly drained sites,Compacted sites.

To reduce salt accumulation in To reduce salt accumulation in the soilthe soil

Improve irrigation uniformity;

Improve drainage;

Leach and flush periodically.

ParameterParameter RWWRWW

Total dissolved salts (ppm)Total dissolved salts (ppm) 514514

Conductivity (dS/m)Conductivity (dS/m) 0.840.84

Sodium (ppm)Sodium (ppm) 9999

Calcium (ppm)Calcium (ppm) 6161

Magnesium (ppm)Magnesium (ppm) 1515

Sodium adsorption ratio (SAR)Sodium adsorption ratio (SAR) 3.13.1


Sodium absorption ratio Sodium absorption ratio (SAR)(SAR)

[Na][Na]

SAR = [Ca]+[Mg]/2SAR = [Ca]+[Mg]/2

Sodium Sodium Effect on Effect on Soil StructureSoil Structure

Sodium ProblemsSodium Problems

Sodium permeability hazard: Sodium permeability hazard:

High SAR (> 12) can induce soil structure High SAR (> 12) can induce soil structure deterioration, including soil sealing, deterioration, including soil sealing, crusting, and reduced water penetration.crusting, and reduced water penetration.

For fine textured soil and heavy traffic For fine textured soil and heavy traffic areas, irrigation water SAR as low as 6-9 areas, irrigation water SAR as low as 6-9 can cause problems.can cause problems.

Sodium Management Sodium Management

I. Chemical amendments of water and soil

Water TreatmentsWater Treatments

Calcium nitrate;Calcium nitrate;

Gypsum (calcium sulfate);Gypsum (calcium sulfate);

Calcium chloride;Calcium chloride;

Soil TreatmentsSoil Treatments

Lime + sulfuric acid injection;Lime + sulfuric acid injection;

GypsumGypsum

Calcium nitrateCalcium nitrate

Calcium chlorideCalcium chloride









Bicarbonate (ppm)Bicarbonate (ppm) 112112


Adjusted SAR: Adjusted by considering bicarbonate, carbonate, and the water’s total salinity, in addition to water’s calcium, magnesium, and sodium content.

Bicarbonate and Adjusted SARBicarbonate and Adjusted SAR

• Bicarbonate can combine with Ca++ and Mg++ to precipitate them out and increase the water SAR;

• Bicarbonate can also raise water pH to undesirable levels;

• If recycled wastewater has high bicarbonate (> 120 mg/L), it is recommended that SAR be adjusted to consider bicarbonate content in the water - SARadj.

To reduce bicarbonate in To reduce bicarbonate in irrigation water irrigation water

Acidification of irrigation water (to 6.5 –7.0 Acidification of irrigation water (to 6.5 –7.0 pH) is effective in converting bicarbonate to pH) is effective in converting bicarbonate to COCO22 and H and H22O. O.










Chloride (ppm)Chloride (ppm) 9595


Boron (ppm)Boron (ppm) 0.230.23


Specific ion toxicities/problemsSpecific ion toxicities/problems

Trees are more sensitive to salts Trees are more sensitive to salts especially sodium and chloride are especially sodium and chloride are sprayed directly onto plant leaves sprayed directly onto plant leaves through irrigation water. through irrigation water.

If irrigation water is applied to roots If irrigation water is applied to roots rather than leaves, plant tolerance level rather than leaves, plant tolerance level to Cl and Na will increase.to Cl and Na will increase.

B is usually absorbed by roots.B is usually absorbed by roots.

Use low angle nozzle to reduce leaf ion Use low angle nozzle to reduce leaf ion toxicity on trees and shrubs.toxicity on trees and shrubs.

Declines of conifer trees have been observed under prolonged use of RWW

Mineral Concentration Mineral Concentration in Ponderosa Pine Needlesin Ponderosa Pine Needles

ParametersParameters Surface Water Surface Water

IrrigationIrrigation

Recycled WaterRecycled Water

IrrigationIrrigation

Firing (0-100%)Firing (0-100%) 3.17****3.17**** 33.5833.58

BB 35.69***35.69*** 50.2750.27

KK 22982298 21282128

NaNa 237****237**** 27502750

K/NaK/Na 9.7****9.7**** 0.80.8

ClCl 13831383 32483248

*, ***, **** Significant at P0.05, 0.001, and 0.0001 respectively.

Pine needle burn and NaPine needle burn and Na++ in the needles in the needles

y = 0.0096x + 4.6998

R2 = 0.7661

0

10

20

30

40

50

60

0 1000 2000 3000 4000 5000 6000

Sodium Concentration in needles (ppm)

Le

af

firi

ng

(0

-10

0%

sc

ale

)










Chloride (ppm)Chloride (ppm) 9595

Boron (ppm)Boron (ppm)

Nitrogen (ppm)Nitrogen (ppm)

0.230.23

10.310.3

Phosphorus (ppm)Phosphorus (ppm) 0.80.8


Nutrients in Irrigation PondNutrients in Irrigation Pond

Test recycled wastewater on regular basis, and calculate N and P input via irrigation. These amounts of N and P should be deducted from the fertilization program.

Increased nutrient content will increase algae Increased nutrient content will increase algae population in irrigation ponds, which will result in population in irrigation ponds, which will result in secondary problems, such as decreased clarity and secondary problems, such as decreased clarity and aesthetic appearance. Some algal metabolites are aesthetic appearance. Some algal metabolites are toxic. toxic.

Irrigation pond maintenance level will increase, Irrigation pond maintenance level will increase, needing additional aeration and chemical needing additional aeration and chemical modification. modification.

To make water reuse a success:To make water reuse a success:

Support water reuse;Support water reuse; Recognize that reused water and fresh water Recognize that reused water and fresh water

are not of equal value and quality;are not of equal value and quality; Yes, we can manage aesthetic appealing Yes, we can manage aesthetic appealing

landscapes, but hidden costs exist.landscapes, but hidden costs exist.

What should be done to manage landscapes What should be done to manage landscapes receiving recycled wastewater?receiving recycled wastewater?

IrrigationIrrigation Regularly monitor water quality.

More vigorous aeration in irrigation pond;

Improve irrigation uniformity;

Irrigate based on ET with additional periodic leaching and flushing;

Improve drainage;

Conversion to low angle nozzles to reduce leaf damage of trees.

What should be done to manage landscapes What should be done to manage landscapes

receiving recycled wastewater?receiving recycled wastewater? Compaction controlCompaction control

More intensive cultivation programs (deep aeration and water injection) to maintain oxygen diffusion and water movement;

More vigorous traffic control.


receiving recycled wastewater?receiving recycled wastewater? Fertilization and AmendmentsFertilization and Amendments

Reduce N and P fertilization;

Fertilize to alleviate nutrient imbalance;

Additional chemical amendments to displace Na;

Add to soil

Add to water

Leaching to remove excess Na after soil amendment treatment;


receiving recycled wastewater?receiving recycled wastewater? Plant SelectionPlant Selection

Replace with more salt tolerant species and cultivars.

Deciduous Woody Plants Deciduous Woody Plants Salinity ToleranceSalinity Tolerance

Pear Pear Cottonwood Cottonwood Siberian Elm Siberian Elm Green Ash Green Ash

Red Maple Red Maple Amur MapleAmur MapleLittleleaf LindenLittleleaf Linden

High

Low

Cool Season TurfgrassesCool Season Turfgrasses

AlkaligrassAlkaligrass

Creeping bentgrassCreeping bentgrassTall fescueTall fescueFine fescuesFine fescues

Perennial ryegrassPerennial ryegrass

Kentucky bluegrass Kentucky bluegrass

High

Low

Related Research at CSURelated Research at CSU

Management Options for Mitigating Sodium Management Options for Mitigating Sodium Stress in Effluent Irrigated Turfgrass SystemsStress in Effluent Irrigated Turfgrass Systems

Research Project at CSU

Sponsored by the City of Westminster, Denver Water,Plum Creek Water Authority, and Castle Pine Golf Club

Treatments: Treatments:

1 2 3 4 5 6 7

Treatment GypsumCalcium chloride Humate

Mycorrhizae (VAM)

Humate

+ Gypsum

VAM +

Gypsum Control

Application Rate

50 lb/ 1000 ft2

1qt/ 1000 ft2

15 lb/ 1000 ft2 1.4 lb/1000 ft2 1 + 3 1 + 4

No amendment

Preliminary FindingsPreliminary Findings

Soil texture is playing a dominant role; Soil texture is playing a dominant role; Mycorrhizae treatment did not help to reduce Mycorrhizae treatment did not help to reduce

sodium problems and improve turf quality, but sodium problems and improve turf quality, but enhanced soil redox status;enhanced soil redox status;

Gypsum (CaSOGypsum (CaSO44) treatment enhanced leaching of ) treatment enhanced leaching of

Na, but did not improve turfgrass quality; Na, but did not improve turfgrass quality; Calcium chloride treatment helped to reduce Na Calcium chloride treatment helped to reduce Na

accumulation and increased turf quality in both accumulation and increased turf quality in both greenhouse and field studies. greenhouse and field studies.

Warren et al. Warren et al. (2005)(2005)

Development and Selection of Development and Selection of Salt Tolerant PlantsSalt Tolerant Plants

Sponsored by US Golf Association

New saltgrass nursery at Colorado State Univ. that contains 3000+ accessions and progenies

Four acres of saltgrass plots at CSU (containing 250 accessions and progenies.)

Selecting Conifers Trees For Landscapes Selecting Conifers Trees For Landscapes

With Recycled Wastewater IrrigationWith Recycled Wastewater Irrigation

Sponsored by Denver Water

urban landscape irrigation with recycled wastewater: water quality and salinity issues yaling qian...

Documents

water quality slide

salinity of irrigation

water source

water reuse practice

shallow water table

potable water shortages

reduced water penetration

sodium ppm