John P. Chastain

Enhanced solid-liquid separation of dairy manure with natural flocculants.

The aim of this study was to determine the effectiveness of natural flocculants to reduce solids and nutrient loads in dairy cow wastewater using solid-liquid separation; chitosan was used as a model. Its use efficiency and optimum application rate were determined using flushed dairy cow manure of varied strengths - 0.4%, 0.8%, 1.6%, and 3.2% total solids (TS) content. Treatments consisted of nine rates of chitosan. The flocculated manure was dewatered using 1-mm and 0.25-mm screens. Separation by screening alone was not effective; average efficiencies were about 60% for total suspended solids (TSS), 22% for total Kjeldahl nitrogen (TKN), and 26% for total phosphorus (TP). Mixing with chitosan before screening substantially increased separation. At optimum chitosan rate (0.5g/L for the highest strength effluent), separation efficiencies were >95% for TSS, >73% for TKN, and >54% for TP. The results of this study indicate that natural flocculants such as chitosan are useful for the solid-liquid separation treatment of livestock wastewater.

EFFECTIVENESS OF LIQUID-SOLID SEPARATION FOR TREATMENT OF FLUSHED DAIRY MANURE: A CASE STUDY

Sunny Day Farm was the home of the highest producing registered Jersey herd in the world at the time this study was conducted. The cows are housed in a freestall barn and manure is removed from the barn using a flush system. The manure treatment system on this farm includes the following components in series: an inclined stationary screen separator, a two–chambered settling basin, and a lagoon. Samples were taken to quantify the performance of the existing manure treatment system. The inclined stationary screen separator removed 60.9% of the total solids, 62.8% of the volatile solids, 49.2% of the TKN, 52.2% of the organic–N, and 53.1% of the total P. The complete on–farm manure treatment system removed 93.0% of the TS, 95.6% of the VS, 74.0% of the TKN, 91.1% of the organic–N, and 86.1% of the total P. In addition, settling experiments were carried out with flushed manure (unscreened) and effluent from the mechanical separator (screened) to determine how well settling of dairy manure could be enhanced with a polymer (PAM) and aluminum sulfate. Addition of 250 to 400 mg PAM/L to screened and unscreened dairy manure significantly increased the removal of total and volatile solids, organic–N, total P, Cu, and Zn. The optimum amount of PAM to add was 300 mg/L for screened and unscreened manure. Settling of flushed dairy manure for 60 min following an application of 300 mg PAM/L removed 76.1% of the TS, 80.3% of the VS, 80.8% of the COD, 45.7% of the TKN, 72.3% of the organic–N, and 61.8% of the total P. The largest amount of TKN and total P was removed by a two–stage separation process that combined the stationary inclined screen separator followed by gravity settling with a polymer or aluminum sulfate. Enhancing the gravity stage with 300 mg PAM/L removed 71.1% of the TKN and 86.0% of the P. Application of 3,194 mg alum/L removed 71.1% of the TKN and 99.6% of the total P.

Removal of Solids and Major Plant Nutrients from Swine Manure Using a Screw Press Separator

A screw press separator was temporarily installed on a commercial swine farm in Horry County, South Carolina. The separator had a 0.5 mm screen and was operated with a single 40 kg weight on each pressure plate arm. Prediction equations were developed from the data to describe the removal of total solids (TS), total volatile solids (VS), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammonium nitrogen (NH4 –N), organic nitrogen (organic–N), and total phosphorus (TP). Separated solids were analyzed to determine the percent total solids and the concentration of major plant nutrients. The concentration of total potassium (TK) in the separator influent and effluent was the same within measurement error. The removal of TS, VS, N, and P was found to vary significantly with the TS concentration of the influent manure. Therefore, building management and the methods used to implement the machine in the manure handling system would have a significant impact on separator performance. The prediction equations were used to calculate separator performance for a typical pit–recharge swine building based on observed characteristics on the cooperator’s farm. The screw press would be capable of removing 14.9% of the TS, 19.6% of the VS, 34.9% of the COD, 9.2% of the TKN, 16.0% of the organic–N, and 14.8% of the TP from the manure added by housed swine.

Using Broiler Litter as an Energy Source: Energy Content and Ash Composition

Broiler farms produce large amounts of litter that is typically spread on nearby cropland or is sold to other farmers for use as a fertilizer substitute. Burning litter biomass to provide energy for space heating in broiler houses or for off-site electric generation has been viewed as an attractive alternative to land application and a source of renewable energy. A large litter sample was obtained from a commercial broiler farm following clean-out to evaluate the energy content, ash yield, and characteristics of ash following combustion. Litter ash was evaluated as a possible lime substitute and fertilizer. The energy content of the broiler litter was 14,425 kJ/kgDM and had an ash content of 24.7% dry basis. Broiler litter ash contained large amounts of Ca and a pH of 11.6, however the calcium carbonate equivalency (CCE) was only 32.4% on a dry basis. It was determined that broiler litter ash should not be used as a liming agent since it would result in excessive application of P2O5, K2O, Cu, Zn, and Na. Small applications of litter ash, on the order of 2 t/ha or less, can provide the P or K needs of a crop and can serve as a source of key micronutrients without application of large amounts of Zn, Cu, or Na. A 1-MW litter fueled electric power plant would provide enough P2O5 in litter ash to fertilize only 1600 ha at a rate of 100 kg P2O5/ha. It was also estimated that only 59% of the electrical generating capacity would be available for use by the distribution system over and above the electricity required by the broiler houses that supply litter to the plant. The amount of litter produced on broiler farms is theoretically adequate to provide enough heat to eliminate the purchase of propane for space heating but is limited by heating system efficiency. The amount of land needed to accommodate the ash from an on-farm litter furnace was estimated to be about 20 ha per broiler house. Many technical and economic obstacles need to be overcome to see large scale use of litter as a source of biomass fuel.

Geotextile Filtration Performance for Lagoon Sludges and Liquid Animal Manures Dewatering

Maintenance and control of liquid levels in anaerobic lagoons and storage ponds is enhanced by pretreatment with liquid-solid separation or periodic removal of accumulated sludges. Until local disposal or nutrient recycling options become available, sludges can be contained, dewatered, and stored using geotextile filtration. A geotextile filtration testing method termed a hanging-bag test was used to treat dairy lagoon sludge, swine lagoon sludge, liquid dairy manure, and liquid swine manure. Hanging-bag performance was evaluated by: (1) determining solids and plant nutrient mass retention efficiencies (MRE), (2) quantifying the overall volume reduction, and (3) characterizing the dewatered manure. After three fill-dewater cycles, geotextile filtration performed similarly for the sludges, retaining an average 87.6% of total solids (TS), 58.4% of total ammoniacal nitrogen (TAN), and 86.7% total phosphorous (TP). Geotextile filtration was also effective in dewatering and concentrating the sludges; by highly concentrating the retained solids, it reduced the total influent sludge volume requiring disposal to less than 18.5%. Despite relatively high MRE values for liquid swine manure (70.2% of TS, 65.1% of TAN, and 75.7% of TP), geotextile filtration was ineffective as a primary liquid-solid separation, with 60.3% of the total influent volume remaining. For liquid dairy manure (TS = 0.71%), geotextile filtration reduced the total influent volume to less than 1%, concentrated the solids and nutrients in the dewatered material 16 to 21 times greater than the influent, and retained 38.4% of TS, 25.8% of TAN, and 45.0% of TP, making this an effective liquid-solid separation technique.

Using Poultry Litter to Fertilize Longleaf Pine Plantations for Enhanced Straw Production

Longleaf pinestraw is high-quality landscape mulch that is in large demand in many urban and suburban areas of the Southeastern United States. In many cases, the annual income from pinestraw production is just as important to forestland owners as the value of the standing timber.

CORRELATION EQUATIONS TO PREDICT THE SOLIDS AND PLANT NUTRIENT REMOVAL EFFICIENCIES FOR GRAVITY SETTLING OF SWINE MANURE

Experiments were performed to determine the amount of TS, TSS, VS, VSS, COD, TKN, organic- N, total-P, organic-P, and total- K that can be removed from liquid swine manure by settling for 60 minutes. The experiments were conducted using manure samples taken from buildings on three different swine farms. All experiments were replicated 3 times. The swine farms included two pitrecharge manure-handling systems and one flush facility. Significant regression equations were developed from the data that allow the prediction of solids and nutrient content of the influent and effluent manure and removal efficiencies over a TS range of 1730 to 23,850 mg/L. The effects of primary treatment on the ratio of available N to P2O5 in the effluent and the impact on the design of further treatment processes will be discussed. These data provide needed information to allow engineers to more precisely design gravity settling structures for primary treatment of swine manure.

AMMONIA VOLATILIZATION LOSSES FOLLOWING IRRIGATION OF LIQUID SWINE MANURE IN COMMERCIAL PINE PLANTATIONS

Ammonia volatilization was measured after land application of liquid swine manure in a commercial pine forest in South Carolina. Three wind tunnels were constructed and used to measure ammonia volatilization after application. The fraction of ammonia lost as percent of TAN applied was fitted to the function ( ) Kt e a - Y - = 1 . The function represented the data with parameter a, the potential volatilization loss, and parameter K, a rate constant. The total amount of NH3-N lost after irrigation of liquid swine manure varied from 0.38% to 3.6% of the TAN applied. The total ammonia lost was found to correlate significantly (R2 = 0.950) with the mass of TAN applied per m2 per application depth (g TAN/ m2-mm) and with the total solids content of the manure. The average rate constant, K, for liquid swine manure applications with mean air temperature below 30 °C was 0.0125 min-1. At mean air temperatures of 32 °C, the rate constant increased to 0.0337 min- 1 and was significantly different from other application events. Ammonia losses following irrigation of liquid swine manure were on the same order of magnitude as losses reported for other land application studies in which the manure was immediately incorporated.

Field Evaluation of a Two-Stage Liquid-Solid Separation System at a California Dairy

A two-stage mechanical separation system was installed on a large dairy farm near Tulare, California to reduce loading on the settling ponds and lagoon and to produce solids to be used as freestall bedding. The system included two inclined screens operated in series. The first separator used a 0.508 mm (0.020 in) screen followed by a low-pressure screw press to provide additional dewatering and a perforated stacking conveyor to stack the residual solids. The second separator was fitted with a 0.254 mm (0.010 in) screen and additional drying occurred on a perforated stacking conveyor. The two-stage system removed 59.7% of the total solids (TS), 65.7% of the volatile solids (VS), but only 22.8% to 34.8% of important major and minor plant nutrients (N, P, Ca, Mg, S). Removal by the first separator accounted for most of the solids and plant nutrient removal. The effluent from the separation system was still rich in valuable plant nutrients and 68.8% of the solids were VS. Therefore, the methane producing potential of the system effluent was still significant. The residue from the first separator had a C:N of 26.6 and would be a valuable substrate for composting. The residue from the second separator had a lower C:N (20.5), but contained a higher concentration of plant nutrients. Residue from the first separator was dried in open lots during the dry season prior to being stored in windrows. The moisture content was reduced from 77.3% to 9.2% prior to use as freestall bedding. Both N and C were lost from the residue during drying and storage.

Estimation of Sludge Accumulation in Lagoons

The results of several studies of sludge accumulation in swine manure treatment lagoons have indicated that the sludge accumulation estimation method provided by ANSI/ASAE EP403.3 (ASAE Standards, 2004) is inadequate for modern swine facilities. This paper describes the development of a new sludge accumulation model based on basic treatment and mass balance principles that will allow the model to be implemented for all animal species in a variety of situations. Model parameters include the addition of total and volatile solids, organic bedding, excess feed wastage, and soil. Physical and biological treatment is described by settling characteristics, the volatile solids destruction rate, and the sludge storage period. Model predictions were compared with all available data and the values in the current standard. It was determined that the model agreed with the majority of the available data within the uncertainty in the model parameters. In the course of the study, additional problems with the current standard were uncovered. The current standard includes two sludge accumulation rates for poultry lagoons - one for layers and the other for pullets. Statistical analysis of the original data indicated that such a distinction was not justified. The sludge accumulation rate for dairy lagoons in the current standard was also found to be in error. The contributions of organic bedding and soil tracked into animal housing facilities by cows were ignored. Furthermore, the current standard does not provide the practicing engineer a method to account for these contributions to lagoon sludge accumulation, or for the influence of primary manure treatment. It was concluded that using constant sludge accumulation rates is not adequate for lagoon design for modern animal production facilities. The new model overcomes this problem by providing a simple, flexible method that allows the practicing engineer to implement site-specific data, and professional judgment.