Extraordinary estuary

Mapping the Hudson Estuary's submerged lands, JW Ladd et al.

PCBs in the Hudson River: Role of sediments, EA Garvey et al.

Hudson River restoration: Role of natural resources trustees, TM Brosnan et al.

Ecosystem indicators for Lake Ontario, F Luckey et al.

Effect of lower chlorine dosage at Buffalo WWTP, KN Irvine et al.

Livestock waste management and lake rehabilitation, CB Lind

President's message

Executive director's message

Plant profiles
   Southtowns STP
   Big Sisters STP
   Lacawana STP
   Holland TP

People and places

Spring 2002 — Vol. 32, No. 1

Applying alum with a “houskeeper”—a machine that removes caked chicken manure and leaves bedding

Agricultural and urban activities often promote the addition of phosphorus, a nutrient, to streams and lakes. Several techniques are available to mitigate such additions including nutrient inactivation, alternative disposal techniques, and dietary modifications to reduce total P in manure. Similarly, phosphorus binding can rehabilitate lakes and streams affected by excessive P.

Mobility of phosphorus

Poultry manure and spent bedding material or litter has been used for crop fertilizer because of its nitrogen value. The phosphorus content of the manure is roughly one-third to one-half of the numeric value of the nitrogen value. That is 26-73 lb N/ton and 7-37 lb P/ton for broiler and caged layer manures and litter (Zublena et al. 1996). Crops need many times more nitrogen than P. The soil can become saturated with P and classified as “eutrophic” at >75 mg P/kg soil (Lind 1997). The P binding capacity of the soil depends on many factors including iron, aluminum, and calcium concentrations; pH; oxygen levels; other ligands and moisture.

The P in excess of crop requirements and not bound in soil can enter surface and subsurface waters through runoff and percolation. This P, either inorganic like dicalcium phosphate or organically bound, is largely soluble and immediately available as an algae nutrient. A large input of P to surface waters results from erosion of the P-laden soil.

The chemistry of the receiving water affects the rate and mechanisms of the release of P from the soil particles. The more loosely sorbed P will be released as bio-available P. The consequence is degradation of surface water supplies, fisheries, and allegedly toxic algae blooms (Shreve et al. 1995).

Livestock and phosphorus

Chicken house for broilers, Springdale, Arkansas

The poultry grower can reap economic benefits from the technologies for nutrient inactivation and interception with aluminum sulfate (alum). The benefits stem from reduced levels of ammonia volatilization with reduced pH and moisture in litter. Litter amendment programs have demonstrated binding of phosphorus and minimization or elimination of atmospheric ammonia emissions; both improve the environment. Various litter amendments have been marketed for odor control over the past two decades. The major classifications have been acids, enzymes, and adsorbents. The objective is reduction or elimination of the evolution of ammonia.

Ammonia in excess of 25 ppm in the poultry house air is harmful to chicks as well as workers. The chicks can become blind and are susceptible to diseases that can kill them or make them unusable as food. Enzymes and adsorbents have met with very limited success and are not in widespread commercial use. They do nothing for P control.

Aluminum sulfate has been employed for reduction of litter pH for the past few years (Moore and Miller 1994). By the hydrolysis reaction each mole of alum produces six moles of acid to buffer the high-pH chicken waste. The end product is aluminum hydroxide, an antacid. It is far more long-lived than sodium bisulfate, producing the desired low pH (4 - 6) for 14-21 days. A benefit of lowering the litter pH is that the environment is less hospitable to vermin, insects, and pathogenic bacteria (Worley et al. 1999, Worley et al. 2000).

Furthermore, the aluminum binds the phosphorus as an insoluble aluminum phosphate. Thus, when the litter is used as a crop fertilizer, the runoff P is unavailable as a nutrient to support large algae populations in surface water. The loss of nitrogen through volatilization of ammonia is reduced making the litter more valuable as a fertilizer. The grower gets a larger healthier and more valuable bird, and the environment suffers less soluble reactive phosphorus and gaseous ammonia.

Aluminum phosphate is the least soluble precipitate of the three common cations used for P control—iron, aluminum and calcium (Stumm and Morgan 1981). It is insoluble between pH 2 and 9 (USEPA), well within the range of soils and surface waters. The presence of organic material, wood fiber (bedding material as well as plant debris), silica, unreacted P in receiving waters and soils, and hydrolysis will essentially remove the bulk of monomeric or polymeric aluminum species present in the waste.

Turkey tiller with spray rig, Willmar, Minnesota

Other techniques involve P interception by binding the P in eutrophic soils. The use of water treatment residuals—predominantly aluminum and/or iron hydroxides—as soil amendments reduce the soluble reactive P in runoff (Haustein et al. 1998, Peters and Basta 1996). Moreover, the high hydroxide content buffers the soil against the effects of acid rain (Novak et al. 1995, Bugbee and Frink 1985) with no significant release of primary metal coagulant (Fe or Al) or heavy metals.

Web extra: Click here for information on Poultry litter production and nutrient value (opens new browser window).

Nutrient reduction strategies

The farmer has optional strategies for nutrient reduction, inactivation, or interception to address phosphorus runoff. Each option offers strengths and weaknesses:

• Alternative manure disposal systems such as incineration, pelletizing, gassification, and composting
• Dietary modifications such as High Available Phosphorus Corn (HAP), enzymes and feed additives to improve nutrient uptake by the birds allowing for lower concentration in manure
• Phosphorus binding by metal salts such as calcium and aluminum that reduce the soluble bioavailable fraction of the P in manure.

Incineration is really a volume reduction technology. The phosphorus is not converted to an insoluble form; so the ash is still a disposal/reuse issue. Moreover, air pollution needs to be assessed. Composting also reduces the manure and litter to a more usable form, but the soluble P remains. Pelletizing to a more easily transported fertilizer allows the waste to be shipped more economically to areas with nutrient deficient soils. Gassification and energy recovery produce a solid fertilizer that, like pellets, can be transported greater distances.

Dietary modifications were touted as one of the most effective approaches to reduce the amount of phosphorus in poultry manure. Feeding birds enzymes like phytase made more of the phosphorus digestible, and thus less P was needed in the ration the birds received. The reality appears to be that the amount of total phosphorus is reduced in the manure, but the soluble fraction is higher. The net effect is more P in the runoff (Moore et al. 2000).

Table 2 shows the difference in the fractions and types of phosphorus in litter and runoff for normal ration (“Normal”) high-available P corn (HAP Corn), phytase feed additive (Phytase) and a HAP + phytase ration.
 
Table 1. Effect of diet modification on soluble P in litter

Ration	Total P (mg/L)	Soluble P (mg/L)	Soluble/total (%)
Normal	111	8	7.2
HAP corn	84	14	16.7
Phytase	66	18	27.2
HAP + phytase	56	4.7	8.4

Feed additives and pelletizing are P control technologies. They do not address the evolution of ammonia from the growing of livestock. Composting actually increases soluble P and produces more ammonia. Reagents that reduce the litter pH, however, are effective. Aluminum sulfate reduces the pH, absorbs litter moisture, and ties up soluble phosphorus in an insoluble non-bioavailable form.

Web extra: Click here for information on Phosphorus binding (opens new browser window).

Agronomic benefits

Application of dry alum with water fog

Reports from the application of alum to houses raising millions of birds confirm that bird health and performance improve. Control of phosphorus runoff will increase the cost of doing business for the livestock producer. Each of the runoff control strategies is a new practice. The use of aluminum sulfate as a litter additive to control soluble phosphorus runoff has benefits:

• Reduced mortality
allows the farmer to sell more birds with fewer to dispose of
• Reduced condemnations
due to healthier birds give the grower a larger payment for birds accepted to the processing plants and saves money at the processing plant in rejected carcass disposal
• Improved feed conversion
means the bird gains weight faster with less feed consumed
• Higher nitrogen content
of the litter adds value as fertilizer
• Lower ammonia
levels in poultry houses are safer for animals.

Lake and stream management

USEPA conducted the earliest whole lake nutrient inactivation program in the U.S. in 1970. Most lake rehabilitation programs using chemical nutrient inactivation are supervised by a Federal or state agency. Since then dozens of water bodies, from ponds less than one acre to lakes of thousand of acres, have been successfully restored.

Mitigating phosphorus runoff is a part of long-term environmental protection. For waters that are eutrophic from inputs of phosphorus, in-lake nutrient inactivation is one part of lake rehabilitation. These actions should be implemented together with nonpoint source pollution prevention practices.

The principle is identical to the phosphorus binding in animal waste management—tie up the phosphorus in a form that algae cannot rapidly assimilate. Algae have no roots and, therefore, must rely on soluble nutrients; that is, particulate forms of phosphorus must chemically or biologically solubilize. In lakes with a substantial input of suspended solids, the burial rate of the particulate P may exceed the rate at which the P is resolubilized. Thus, the binding and interception of soluble P can be the major influence in restoring the lake.

Aluminum compounds have the most widespread use for in-lake treatment, but iron and calcium compounds are also effective. Iron is best when accompanied by an aeration system to prevent the release of ferrous phosphates. Calcium salts typically raise the pH of the lake too high. They are not used except for special applications such as calcium nitrite for sediment treatment.

Both iron sulfate and aluminum sulfate consume alkalinity in the water by means of hydrolysis. In low pH or poorly buffered water, care must be taken to avoid depressing the pH and shocking the biota. In these instances, an alum to sodium aluminate addition rate of 2:1v/v provides excellent P binding and maintains circumneutral pH values in the receiving water (Eberhardt 1997).

Feed lot lagoon

Precipitation of phosphorus

The use of chemical precipitants is well established to restore water bodies affected by nutrients. Chemical coagulation and clarification are important means of nutrient inactivation and management in surface waters. The precipitation and removal of the phosphorus from the water column and subsequent deposition and sealing in sediments has a 30-yr history of lake restoration when used in conjunction with sound watershed management practices. High quality recreational waters are only part of the benefit. Providing a safe and reliable potable water supply, free from objectionable tastes and odors caused by uncontrolled algae growth, is the major impetus in many areas.

Microbial proliferation will manifest as an increase in the NOM (natural organic matter) or TOC (total organic carbon) level in the lake or reservoir. The NOM may include disinfection by-product precursors (DBP) and taste- and odor-producing chemicals. The DBPs are suspected carcinogens, and algal toxins have been implicated in a variety of health effects in humans and animals. Algal toxins are on USEPA's Candidate Contaminant List for potential inclusion in the drinking water regulations.

These organic compounds are often very difficult to remove by conventional activated carbon adsorption and oxidation; they must be coagulated from the water at significant extra expense. .Bd Far less expensive is the nutrient management to intercept the nutrients before they fertilize massive blooms. Taste- and odor-causing compounds often do not respond to adsorbents and oxidants like powdered activated carbon and ozone. So, coagulants are one of the most important chemicals fed to purify drinking water supplies and manage the quality of the source waters.

The application of the precipitants is straightforward. Specialized applicators use Global Positioning Systems to ensure minimal overlap or missed spots. New technology allows operators to navigate the application vessel to within a fraction of a meter to where they left off. This important feature makes sure that just enough precipitant is used.

Newer vessels have two distinct chemical storage and addition systems so that chemicals for buffering or other treatments can be simultaneously injected minimizing the interruption of normal lake activity. The common products, alum, ferric sulfate, and sodium aluminate are liquid chemicals that react essentially instantaneously. Normal lake activity often continues around the application boat.

The following table offers the stoichiometric requirements on a weight basis to remove one unit of phosphorus and the typical commercial products used as phosphorus binding agents.
 
Table 2. Chemicals used in phosphorus inactivation —
Theoretical metal: Phosphorus requirements.

Metal	Metal:P requirement	Chemical forms available
Aluminum (Al3+)	0.87:1	Alum, aluminum chloride, sodium aluminate, PACl, ACH
Ferric iron (Fe3+)	1.8:1	Ferric sulfate, ferric chloride
Ferrous iron (Fe2+)	3.2:1	Ferrous sulfate, ferrous chloride pickle liquor, copperas
Calcium (Ca2+)	1.93:1	Lime, quicklime, calcium oxide, calcium chloride, calcium sulfate

Storm water treatment

Another technology for lake rehabilitation is continuous injection of alum to flowing storm water. Urban and suburban runoff is as nutrient-laden as agricultural runoff. With one approach, flow sensors dose alum to the storm water in proportion to volume. In poorly buffered waters, pH sensors adjust the pH with caustic soda. This has been successfully employed in Florida, New Jersey and elsewhere for over 10 years. Florida has over thirty such installations.

Aside from the benefit of fewer algae choking the lakes and an improvement in water quality, the rate of sedimentation is dramatically reduced. The addition of alum creates aluminum hydroxide and aluminum phosphate precipitants that settle as solids to the bottom of the lake. This thin layer acts to seal soluble phosphorus in the sediments, keeping it from resuspending as a nutrient. The layer of solids works its way into the bottom mud and becomes an integral part of the sediment. Lakes not receiving treated storm water have massive amounts of algae growth that deposits as thick layers of smelly sediment.

Beef feed lot lagoon treatment and D.A.F. discharge

The cost of these systems varies based on water quality, volume to be treated, cost of land, and construction. Lake Ella, Florida was one of the first such systems. The cost including sewers to collect the runoff was around $200,000. Alum costs were less than $40 per million gal treated (Harper and Herr 1999).

Summary

Since 1970 shallow lakes, deep lakes, mixed lakes, and stratified lakes have been treated for water column and sediment nutrient inactivation. Nutrient binding with aluminum sulfate is not a panacea, but it is an effective component of lake and river rehabilitation. It provides these advantages:

• Nutrient diversion and interception
• Nonpoint source nutrient management
• Animal waste management
• Urban storm water treatment
• Macrophyte management
• Fisheries management
• Nutrient inactivation

Phosphorus binding and nutrient inactivation of animal wastes can be an integral part of watershed management. It is simple and employs familiar chemistry and common chemicals. Controlling the influx of soluble phosphorus and inactivating the nutrients already in the sediments and water column can be effective in rehabilitating eutrophic lakes and rivers.
 
Click here for References (opens new browser window).
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Christopher B. Lind is the director of environmental products and services at General Chemical Corporation in New Jersey. Phone 973-515-1861.