Table 1 Manure Characteristics of Dairy Cattle

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Weight of dairy cattle (lbs)a 150 250 500 1000 1400

Daily production (lbs/day) Daily production (gallons/day) Total solids (lbs/day) Volatile solids (lbs/day) BOD5 (lbs/day) Nitrogen (lbs/day) Phosphate (lbs/day) Potash (lbs/day)_

flowing onto an animal feeding operation, and other materials polluted by livestock [1,35]. Livestock and poultry wastes can be categorized as solid, semisolid, and liquid wastes. Solid waste contains more than 20% solids, such as bedding and waste feed. Waste is deemed semisolid if it has 10-20% solids. Liquid waste has less than 10% solids. For systems designed to transfer wastes by pumping, the optimum liquid waste contains less than 4% solids.

Both quantity and quality of livestock waste can vary significantly from farm to farm; they are also greatly dependent on animal species, age, ration, and production systems. Tables 1 and 2 show the characteristics for dairy cattle, sheep, horse, and poultry species. Typical waste parameters of dairy, swine, and chicken are listed in Table 3. The impact of age, species, ration, and production system are as follows:

• Animal age. Manure from mature animals is not as biologically stable as that from younger ones. The larger an animal, the more manure it produces (Table 1). A rough estimate of the amount of manure produced per day is 8% of the animal's body weight.

• Animal species. Livestock manure characteristics can differ greatly among animal species. For example, since nonruminant animals cannot digest high-cellulose feed, they can produce relatively more manure than ruminant animals.

Table 2 Manure Characteristics of Sheep, Horse and Poultry.

Poultry

Table 2 Manure Characteristics of Sheep, Horse and Poultry.

Poultry

Animal species

Sheep Horses Layers Broilers

Size of animal (lbs)

100

1000

4

2

Daily production (lbs/day)

4.0

45

0.21

0.14

Daily production (gallons/day)

0.46

5.63

0.027

0.018

Total solids (lbs/day)

1.00

9.4

0.053

0.036

Volatile solids (lbs/day)

0.85

7.5

0.037

0.025

BOD5 (lbs/day)

0.09

0.014

0.0023

Water Content (%)

75

79.5

74.8

74.8

Nitrogen (lbs/day)

0.045

0.27

0.0029

0.0024

Phosphate (lbs/day)

0.015

0.105

0.0025

0.00123

Potash (lbs/day)

0.039

0.205

0.0014

0.0009

Table 3 Typical Wastewater Parameters of Dairy, Cattle, Swine, and Chicken

Parameter

Dairy manure Swine manure Chicken manure

Table 3 Typical Wastewater Parameters of Dairy, Cattle, Swine, and Chicken

Parameter

Dairy manure Swine manure Chicken manure

BOD5 (mg/L)

14,000

28,000

36,000

DM (%)

10

10

18

TS (mg/L)

100,000

9,800

180,000

Total nitrogen (mg/L)

3,800

4,600

1,090

Total phosphorus (mg/L)

800

1,600

940

Note: DM, dry matter.

Note: DM, dry matter.

• Ration. Diet affects the characteristics of the manure. Digestibility, protein, and fiber content of rations are important factors. For instance, cattle fed high-concentrate rations do not produce as much manure as cattle fed high-roughage rations.

• Production system. The production system affects whether the manure is solid, semisolid, or liquid. For example, if large amounts of bedding are used, the manure will be more solid. On the other hand, if a flush-type handling system is used, the manure will be more liquid due to the manure being diluted by the flush water.

Manufacturing plants producing different products will in turn produce different amounts and types of wastes. For instance, the average waste volume coefficients for the dairy industry in general, and cheese producers in particular, were 2.43 and 3.14m3 wastewater/ton milk processed, respectively [8].

Three main crop nutrients—nitrogen, phosphorus, and potassium—and the dry matter (DM) content are the most important in livestock manure due to their great environmental impact on rivers and estuaries [9].

Nitrogen is a major concern in livestock and poultry manure. It exists in the forms of organic nitrogen, ammonia, nitrite, and nitrate. Total Kjeldahl nitrogen (TKN) includes organic nitrogen and ammonia.

Manure degradation is a source of nitrogen oxides (NOx), contributing to accumulation of greenhouse gases. Volatilization of ammonia (NH3) can causes "acid rain," which acidifies soils and woodlands. It was reported that animal sources in Western Europe are responsible for 50% of the acid precipitation. Emissions of nitrous oxide (N2O) during the nitrification-denitrification cycle can contribute to ozone depletion [1,5,10].

Application of manure as a fertilizer can result in excessive quantities of nitrogen, which may contaminate ground or surface waters through surface runoff and leaching. Ammonia can be oxidized to nitrite and then to nitrate, which depletes dissolved oxygen (DO) in the water and thus causes toxicity to fish and other living organisms in surface waters [2-5].

Nitrate leaching is considered another major concern to livestock farms today. The transformation of nitrogen is illustrated in Figure 2. Nitrogen enters to the waters by runoff, erosion, leaching, and volatilization (e.g., NH3). The amount may be significant. Normally, the nitrogen loss is 31-50%, 60-70%, and 75% for poultry, cattle, and swine, respectively. In all manure land application operations, about 13% available manure nitrogen exceeds crop system need. Nitrogen conversion in manure can also be a source of odors. Ammonia may become a health hazard affecting the performance, morbidity, and mortality of the animals and poultry. In drinking water, nitrate concentrations above 10 ppm are a health threat to humans, particularly infants [2-5,11].

Phosphorus is another key element in livestock and poultry waste. The typical phosphorus lost is about 15%. In all manure land application operations, about 25% available manure phosphorus exceeds crop system need. In other words, phosphorus is over-applied. Unlike nitrogen, excess phosphorus in manure does not leach through the soil into the groundwater. It is

Volatilisation (NH3l COjH VOC„ fiti)

Volatilisation (NH3l COjH VOC„ fiti)

Water ptriluttnn (leaching, iUTface mil oil", 6tc) and salid wajic

Water ptriluttnn (leaching, iUTface mil oil", 6tc) and salid wajic

Figure 2 Transformation of pollutants released to the environment.

not toxic and has minimal environmental impact. However, its presence could cause additional consumption of alum in drinking water treatment if it precipitates with aluminum ions (Al +). Phosphorus is a nutrient that limits biological activity in most of the clear water lakes, reservoirs, and streams. Hydrogen, oxygen, carbon dioxide (CO2), and nitrogen of sufficient quantities are naturally present in the water environment to support the growth of algae and plants. Insufficient phosphorus in most inland water bodies keeps the clear water lakes and streams from being congested with plant growth. If concentration of phosphorus exceeds a critical value, acceleration of eutrophication will be observed. As a result, the DO can be depleted, which can cause the death of aquatic species and release of toxins from the blue-green algae. These consequences in turn can increase the treatment costs of drinking water. Advanced eutrophication can also reduce aquatic wildlife populations and species diversity by lowering DO and increasing the 5-day biochemical oxygen demand (BOD).

Potassium is a crop nutrient that is found in livestock manure in significant amounts. Potassium is the main cation within cells in plants. It plays an important role in guard cell operation and functions as a cofactor for some enzymes. Potassium is a limiting plant nutrient as plants have a higher demand for it. Potassium deficiency is particularly common on heavily cropped land. As a result, addition of potassium fertilizers is necessary for the maintenance of soil fertility. Potassium also plays a key role in control of the balance of electrical potentials across cell membranes in human beings and is involved in nerve impulses [11]. It can contribute to the salinity of manure, which in turn may change the salinity in both surface and subsurface waters contaminated by the manure. Fertility of the soil may be reduced if potassium content is too high.

In manure waste, solids, organic matter, pathogens, salts, trace elements, odorous compounds, antibiotics, as well as pesticides and hormones, play important roles in water pollution.

The sources of solids include animal manure, spilled feed, bedding and litter materials, hair, feathers, and corpses. Solids measured as dry matter (DM), total suspended solids (TSS) or total solids (TS), are the mass of solids, as a percentage of the overall mass of diluted livestock manure. Solids may be measured as total dissolved solids (TDS). The presence of the solids can result in high turbidity of waters; they can also act as adsorption sites for metals and other contaminates.

Manure contains a high organic content. Its wastewater normally has a BOD5 of 10,000-50,000 mg/L. Such high contamination levels can significantly reduce the DO in the waters due to biochemical reactions, which can be harmful to fish and other aquatic organisms. The reactions can also change the natural acidity of water, also harmful to aquatic life [1,6].

Salts from livestock waste, such as calcium, magnesium, sodium, potassium, chloride, sulfate, carbonate, bicarbonate, and nitrite, can be released to the water environment. They result from undigested feed. Higher accumulation of the salts can deteriorate soil structure, lower permeability, contaminate surface and ground waters, and reduce crop yields. Trace elements in the salts, such as arsenic, copper, lead, boron, molybdenum, mercury, and nickel are also important because of their higher toxicity [2-4].

Livestock manure contains a significant amount of pathogens including bacteria, viruses, protozoa, and parasites. They enter the waters through various pathways. The obvious species are the protozoa Cryptosporidium parvum and Giardia species, and bacteria Escherichia coli and Salmonella species. They are normally associated with health-related problems, such as food-borne disease. They may be able to survive and remain infectious for a long period of time. These negative effects can render waters unsuitable for consumption or recreational purposes [2-5,12].

Antibiotics, pesticides, and hormones are used in livestock production, and are eventually released to the aqueous environment. Use of antibiotics can cause their presence in waters as well as the development of antibiotic-resistant pathogens. Pesticide and hormones can result in various long-term environmental problems, especially through the food chains [6,11].

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