Use of Reclaimed Water and Sludge in Food Crop Production (1996) / Chapter Skim
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2 Municipal Wasterwater, Sewage Sludge, and Agriculture
2 Municipal Wasterwater, Sewage Sludge, and Agriculture
Pages 17-44
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From page 17... ...
By the turn of the century, there were about a dozen sewage farms in the United States. However, the need for a reliable outlet for wastewater was not entirely compatible with the seasonal nature of nutrient and water requirements of crop production.
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From page 18... ...
per capita per day of municipal wastewater is generated (Solley et al., 1993~. Municipal wastewater treatment plants (otherwise known as publicly-owned treatment works or "POTWs")
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From page 19... ...
With advances in wastewater treatment technology, wastewater effluents can achieve consistently high quality and are increasingly reclaimed for reuse. The value of reclaimed water in crop irrigation has long been recognized, particularly where fresh water resources are limited (Webster, 1954; Mertz, 1956; Sepp, 1971~.
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20 The Use of Reclaimed Water and Sludge in Food Crop Production TABLE 2. ~ Composition of Secondary Treated Municipal Wastewater Effluents arid irrigation Water Secondary Effluents Irrigation Water Parameter RangeTypical Colorado Riverb Quality CriteriaC Total Solids U425 U NA Total Dissolved Solids 200-1300400 668.0 <2000 pH 6.8-7.77.0 7.9 6.5-8.4 Biochemical Oxygen Demand 2-50 25 U NA Chemical Oxygen Demand 25-100 70 U NA Total Nitrogen 10-30 20 U <30 Ammonia Nitrogen 0.1-25 10 U NA Nitrate Nitrogen 1-20 8 0.1-1.2 NA Total Phosphorus 5-40 10 <0.02 NA Chloride 50-500 75 55-77 < 350 Sodium 50-400 100 71-97 <70 Potassium 10-30 15 4-6 NA Calcium 25-100 50 66-163 NA Magnesium 10-50 20 23-28 NA Boron 0.3-2.5 0.5 0.10-0.54 < 3.0 Cadmium (ug/L)
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From page 21... ...
and toxic organic chemicals has been addressed for a variety of end uses of reclaimed wastewater, but they have not been regulated for purposes of agricultural irrigation. As mentioned, concentrations of trace elements in wastewater effluents that have undergone secondary or higher levels of treatment are normally within existing guidelines for irrigation water quality criteria (see Chapter 4 for a discussion of trace elements and organic chemicals)
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From page 22... ...
Many of these toxic chemicals are removed from the wastewater and concentrated into the sewage sludge by the wastewater treatment process. Sewage sludge also contains human pathogens, although it can be treated to significantly reduce the number of pathogens present.
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From page 23... ...
The World Health Organization is also investigating ways to develop human health-related chemical guidelines for using treated municipal wastewater effluents and sewage sludge in agriculture production (Chang, et al., 1993~. Since the late 1970s and early 1980s, source control and industrial wastewater pretreatment programs have been initiated to limit the discharge of industrial pollutants into municipal sewers.
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From page 24... ...
IRRIGATION WITH RECLAIMED WATER Crop Irrigation The nation encompasses 930.8 million hectares (2,300 million acres) of land, of which 125 million hectares (309 million acres)
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From page 25... ...
In 1990, crop irrigation accounted for 518 million m3/day (137,000 million gal/day) of water or 41 percent of all fresh water withdrawn for all uses from well and surface water (Solley et al., 19931.
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From page 26... ...
26 Me Use of Reclaimed Water aru' Sludge in Food Crop Productior' TABLE 2.5 Metal Concentrations in Studges (in mg/kg dry weight) at Two Philadelphia Wastewater Treatment Plants in Response to Pretreatment Programs Year Cd Cu Pb Ni Zn Southwest 1974 31 825 1,540 100 3,043 1976 27 1,110 2,710 103 2,650 1977 27 1,400 2,170 185 3,940 1978 16 1,020 1,800 275 4,050 1980 18 986 740 98 2,780 1981 25 971 562 117 2,300 1982 20 940 1,030 113 2,440 1983 12.5 736 421 79 1,700 1984 14.3 1,140 427 111 1,830 1985 15.0 880 373 80 1,730 Northeast 1974 108 1,610 2,270 391 5,391 1976 97 2,240 2,570 372 5,070 1977 71 2,320 2,680 459 3,920 1978 57 1,240 1,620 319 5,910 1980 26 1,210 728 275 3,890 1982 14 985 423 185 2,570 1983 10.9 1,020 351 130 2,110 1984 12.4 1,200 360 130 1,980 1985 17.3 1,270 382 187 2,100 Note: Source identification began in 1976.
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From page 27... ...
74.7* Chlorodane 16 0 6.4 Dieldrin 16 4 6.4 Heptachlor 16 0 6.4 Hexachlorobenzene 16 0 155 Hexachlorobutadiene 5 0 23 Lindane 16 0 6.4 Dimethylnitrosamine 5 0 57 PCB's N/A N/A -- Toxaphene 16 0 6.4 Trichloroethene 84 1 8139 DDD/DDE/DDT N/A N/A -- Trace Elements (mg/kg, values in O denote composited means by mans in NSSS)
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28 The Use of Reclaimed Water and Sedge in Food Crop Production Other food (23.58%) Other crops (6.36%)
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From page 29... ...
in California, agricultural irrigation accounts for approximately 63 percent of the total volume of reclaimed water (California State Water Resources Control Board, 19901. Even so, only 5 percent of California's reclaimed water irrigates land used to grow crops classified for human consumption (Figure 2.4, EPA, 1992~.
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From page 30... ...
Distribution of irrigated acreage In the conterminous United States, 1987 ~ ~ ~ .
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From page 31... ...
In all other regions, the amount of water required by irrigation far exceeds the volume of wastewater produced (Solley, et al., 19931. Water conveyance is a significant cost of a water reuse project and even in the semi-arid and arid western states, the distance between generators and potential users of reclaimed water will determine its feasibility.
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From page 32... ...
Therefore, both water shortage and waste disposal are driving forces for the use of reclaimed wastewater, and the dominance of one over the other will depend on local conditions. A recent survey of water reuse projects in California indicated that two thirds of the projects were initiated exclusively for water supply purposes.
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From page 33... ...
These rates are considerably less than the amortized unit cost for developing and maintaining a water reclamation facility. If the farmers currently obtain irrigation water at low prices, they are not expected to pay more for using reclaimed water.
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USE OF SEWAGE SLUDGE IN AGRICULTURE Potential Role of Sewage Sludge In Crop Production Based on estimates of the amount of solids produced in typical primary and secondary wastewater treatment processes (Metcalf and Eddy, 1991) , the national production of sewage sludge is approximately 7 million metric tons/year.
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From page 35... ...
If wastewater treatment authorities in urban centers cannot overcome the variety of obstacles to use sludge within reasonable transportation distances, they face the consequences of long distance transportation and its associated costs. These geographical and economical constraints on land application create uncertainty over how much of the nation's sewage sludge will be applied on cropland in the long run.
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From page 36... ...
36 The Use of Reclaimed Water aru' Sedge in Food Crop Production TABLE 2.9 Amount of Cropland Required to Accommodate In-state Sludge Applications at Agronomic Rates Sludge Cropland Producedb RequiredCCroplandd Percent of Populationa (thousands of (thousands of(thousands of State State (millions) metric tons)
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From page 37... ...
bSludge production estimates assume 75 % of population is sewered and produces .073 kg of sludge per person per day. CState cropland required if all sludge produced in-state were to be applied at agronomic rates using the assumption of 4 percent available nitrogen dry weight and an application rate of 100 kilograms per hectare per year.
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From page 38... ...
Thus far, the research indicates that old-field ecosystems are ecologically safe and economically viable sites for sludge disposal (Mary and Barrett, 1984; Carson and Barrett, 1988; Levine et al., 1989; and Brewer
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From page 39... ...
The chemical composition of most treated effluents is within the range defined by accepted irrigation water quality criteria and is comparable to that of water commonly used in crop and landscaping irrigation. At present, treated municipal wastewater probably accounts for much less than one percent of national irrigation water requirements, and it is likely that the level of agricultural use will not significantly increase.
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From page 40... ...
1985. Municipal wastewater: treatment and reclaimed water characteristics in Irrigation with reclaimed municipal wastewater, a guidance manual, G
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From page 41... ...
1995. Impacts of Municipal Wastewater Treatment: A Retrospective Analysis.
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From page 42... ...
California State Water Pollution Control Board Publication No. 15, Sacramento: California State Water Pollution Control Board.
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From page 43... ...
1985. Trngation with Reclaimed Municipal Wastewater A Guidance Manual.
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From page 44... ...
1985. Irrigation water quality criteria in Irrigation with Reclaimed Municipal Wastewater, A Guidance Manual, G
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