Anaerobic Lagoon Research Articles

Variability of Anaerobic Animal Waste Lagoon delta15N Source Signatures

High ammonium-N concentrations derived from animal wastes stored and partially treated in earthen anaerobic lagoons at confined feeding facilities can seep to groundwater. δ15N-NH4 + values from +2.0 to +59.1‰ in 13 lagoons complicate identification of lagoon seepage as well as land-applied lagoon effluent in ground and surface waters. The spectrum of δ15N values requires site-specific isotope characterization of the potential source. Feed and fresh manure and urine δ15N values indicate that most N isotopic fractionation occurs after excretion. Lagoon management clearly affects enrichment. δ15N-total Kjeldahl N (TKN) and δ15N-NH4 + within each lagoon were not statistically different. δ15N-NH4 + within the top 1.5 m of the lagoons was spatially uniform (CV [coefficient of variation] < 5%).

The effect of stratification and seasonal variability on the profile of an anaerobic swine waste treatment lagoon

In this study, the characterization of an anaerobic swine waste treatment lagoon from a farrowing operation (∼2000 sows) was carried out to examine the dynamics of the system due to stratification and seasonal variability. Swine waste samples were taken at different depths with a pulley system equipped with a special sampler that allows for sampling exclusively at certain depth. Chemicals and microbial dynamics were monitored throughout a one-year-period. Results showed that nutrient (C, N, P, S) concentrations varied according to stratified lagoon layers and season. Trace minerals (Al, Ca, Fe, and Mg), on the other hand, appeared to be affected more by stratification than seasonal variability. Molecular analysis also showed that microbial community structure appeared to be affected by the stratification and seasonal variability. Based on these data, it is important to consider the effect of stratification and seasonal variability in managing these open lagoons.

Reduction of Salmonella in dairy waste through anaerobic lagoon and constructed wetland

Reduction of Salmonella in dairy waste through anaerobic lagoon and constructed wetland

Optimisation of biogas production from anaerobic digestion of agro-industrial waste streams in Brazil

The important Brazilian agro-industry produces significant amounts of wastewater with high concentrations of biodegradable compounds. A lot can be gained if wastewater treatment would take place using anaerobic reactors instead of the anaerobic lagoons generally used now. Apart from preventing methane emissions to the atmosphere this would permit the use of the biogas as a source of energy. To facilitate implementation of this technology also in small and intermediate sized companies a system requiring only minimal maintenance is needed. The need for maintenance by skilled labour can be reduced using an automated process control system, which is being developed. Cassava (manioc, tapioca) processing wastewater has been treated in a lab scale UASB reactor equipped with an on-line monitoring system, to test a control strategy based mainly on pH control. Good results have been obtained treating not only pre-acidified but also treating raw (diluted) cassava processing wastewater.

Water Quality Improvements of Wastewater from Confined Animal Feeding Operations after Advanced Treatment

Current trends of animal production concentration and new regulations promote the need for environmentally safe alternatives to land application of liquid manure. These technologies must be able to substantially remove nutrients, heavy metals, and emissions of ammonia and odors and disinfect the effluent. A new treatment system was tested full-scale in a 4360-swine farm in North Carolina to demonstrate environmentally superior technology (EST) that could replace traditional anaerobic lagoon treatment. The system combined liquid-solids separation with nitrogen and phosphorus removal processes. Water quality was monitored at three sites: (i) the treatment plant as the raw manure liquid was depurated in the various processes, (ii) the converted lagoon as it was being cleaned up with the treated effluent, and (iii) an adjacent traditional anaerobic lagoon. The treatment plant removed 98% of total suspended solids (TSS), 76% of total solids (TS), 100% of 5-d biochemical oxygen demand (BOD(5)), 98% of total Kjeldahl nitrogen (TKN) and NH(4)-N, 95% of total phosphorus (TP), 99% of Zn, and 99% of Cu. The quality of the liquid in the converted lagoon improved rapidly as cleaner effluent from the plant replaced anaerobic lagoon liquid. The converted lagoon liquid became aerobic (dissolved oxygen, 6.95 mg L(-1); Eh, 342 mv) with the following mean reductions in the second year of the conversion: 73% of TSS, 40% of TS, 77% of BOD(5), 85% of TKN, 92% of NH(4)-N, 38% of TP, 37% of Zn, and 39% of Cu. These findings overall showed that EST can have significant positive impacts on the environment and on the livestock industries.

Greenhouse Gas Balance for Composting Operations

The greenhouse gas (GHG) impact of composting a range of potential feedstocks was evaluated through a review of the existing literature with a focus on methane (CH(4)) avoidance by composting and GHG emissions during composting. The primary carbon credits associated with composting are through CH(4) avoidance when feedstocks are composted instead of landfilled (municipal solid waste and biosolids) or lagooned (animal manures). Methane generation potential is given based on total volatile solids, expected volatile solids destruction, and CH(4) generation from lab and field incubations. For example, a facility that composts an equal mixture of manure, newsprint, and food waste could conserve the equivalent of 3.1 Mg CO(2) per 1 dry Mg of feedstocks composted if feedstocks were diverted from anaerobic storage lagoons and landfills with no gas collection mechanisms. The composting process is a source of GHG emissions from the use of electricity and fossil fuels and through GHG emissions during composting. Greenhouse gas emissions during composting are highest for high-nitrogen materials with high moisture contents. These debits are minimal in comparison to avoidance credits and can be further minimized through the use of higher carbon:nitrogen feedstock mixtures and lower-moisture-content mixtures. Compost end use has the potential to generate carbon credits through avoidance and sequestration of carbon; however, these are highly project specific and need to be quantified on an individual project basis.

Pasture-Based Dairy and Water Hyacinth (Eichornia Crassipes) for Reduced Biological Oxygen Demand in Dairy Discharge Water

Degradation of surface water quality through point and non-point source pollution is a major problem worldwide. Elevated biological oxygen demand (BOD5) in a waterbody results in the depletion of dissolved oxygen and subsequently adversely impacts on aquatic life. Discharge water from a dairy facility is enriched with oxygen-demanding substances such as total nitrogen (TN), total phosphorus (TP) or organic carbon, and has elevated BOD5. Therefore, it is important to have a sufficiently reduced BOD5 concentration in dairy discharge water prior to discharging it to the natural streams or waterways. The authors compared BOD5 in discharge water from confined dairy and pasture-based dairy, and assessed the effectiveness of the water hyacinth (Eichornia crassipes) for BOD5 reduction in dairy discharge water at UL Lafayette Research Farm in Cade, Louisiana. The dairy wastewater treatment system consisted of a first anaerobic lagoon and a second facultative lagoon. From 1985 to 2005, water samples were collected at least once a month by the grab method at the outlet of the facultative lagoon. These were analysed for BOD5, total suspended solids (TSS) and pH as per the compliance requirements of the Louisiana Department of Environmental Quality. In 2003, the second pond was divided into two halves and water hyacinths were introduced into one half of the pond. Water samples were collected for one year in seven sampling events by the grab method from the following four locations: inlet and outlet of the first pond, and each outlet of the divided second pond. Water samples were analysed in the lab for BOD5, TSS, total combustible solids (TCS), TN, nitrate/nitrite-N (NO3/NO2-N) and TP; while pH and temperature were determined in the field. Wastewater inflow data and dairy herd data were obtained from the records. The average BOD5 concentration of discharge water from pasture-based dairy was 28% lower compared with the confined dairy. Water hyacinths reduced BOD5 concentration by 30.2%, TN by 44% and TP by 19.4% compared with the pond without water hyacinths. Pasture-based dairy and the introduction of water hyacinths in the dairy wastewater treatment system show the potential for reducing BOD5 and oxygen-demanding substances, as well as minimizing surface water pollution and related environmental degradation from a dairy operation.

Evaluation of a new fixed-bed digester design utilizing large media for flush dairy manure treatment

A new anaerobic digester design for the treatment of diluted (<2% solids) flush dairy manure was evaluated. The new design was developed as an economic alternative for enhancing the performance of anaerobic lagoon systems in cold weather areas. The digester employed used automobile tires as fixed-bed media to improve bacterial retention. The digester was heated by steam injection and built underground to enhance insulation. The tires were sorted in a unique pattern for improving mixing and uniform temperature distribution. The system was tested on a pilot-scale. The treatment mechanism was explored by mathematical modeling. The observed treatment efficiency of the new design was comparable to that of conventional digesters operating at higher total solids concentrations (>4%). With a hydraulic retention time (HRT) of 17 days, the measured removal rates were 30–50% and 40–60% of TVS and COD, respectively. The new digester maintained longer solids retention time (SRT) as estimated using the model, supported by the observed thick biofilm formation and resistance to hydraulic overload. The model was used to analyze different operation scenarios varying both the organic and hydraulic loads.

Size-fractionation and characterization of landfill leachate and the improvement of Cu2+ adsorption capacity in soil and aged refuse

Leachate was collected from an anaerobic lagoon at Shanghai Laogang refuse landfill, the largest landfill in China, and the sample was separated into six fractions using micro-filtration membranes, followed by ultra-filtration membranes. Several parameters of the samples were measured, including chemical oxygen demand (COD), total organic carbon (TOC), total solids (TS), pH, total phosphate (TP), total nitrogen (TN), fixed solids (FS), NH4+, orthophosphate, color, turbidity, and conductivity. These parameters were then quantitatively correlated with the molecular weight cutoff of the membrane used. Organic matter in the dissolved fraction (MW<1kDa) predominated in the leachate, accounting for 65% of TOC. Thermal infrared spectroscopy was used to characterize the filter residues. Asymmetric and symmetric stretching of methyl and methylene groups, and of functional groups containing nitrogen and oxygen atoms, were observed. In addition, the ability of two different samples to adsorb heavy metals was tested. Cu2+ was chosen as the representative heavy metal in this study, and the samples were soil; aged refuse, which had spent 8 years in a conventional sanitary landfill; and samples of soil and aged refuse treated for 48h with leachate in the ratio of 5g of sample per 50ml of leachate. Cu2+ uptake by the raw soil was approximately 4.60microg/g, while uptake by the leachate-contacted soil and leachate-contacted aged refuse were 5.66 and 5.11microg/g, respectively. These results show that the organic matter in the leachate enhanced the capacity of aqueous solutions to adsorb Cu2+.

Effect of Yeast Culture on Efficiency of Nutrient Utilization for Milk Production and Impact on Fiber Digestibility and Fecal Particle Size

Approximately 260 Holstein cows on a commercial dairy were utilized in a switchback study. Treatments consisted of control or 56 g/d of yeast culture. The objectives of this experiment were to quantify the benefit of yeast culture on 1) efficiency of milk production, and 2) nutrient flows within the dairy system that utilizes a solids separator. Milk yield was recorded every 12 d. Pen feed intakes and refusals were recorded daily. Manure fiber particle size was determined from fecal grab samples via wet sieving. In addition, a mixture of feces plus water was sieved through a screen to replicate a manure solids separator. Cows receiving yeast culture showed numerically greater DMI (0.13 kg/d), an increase (P < 0.001) in BW gain, greater milk fat content (P < 0.02), greater (P < 0.08) milk fat yield, less milk protein content (P < 0.03), and similar milk protein yield (P > 0.05). Milk yields were similar between treatments; however, there was a trend for an increase (P < 0.19) in 3.5% fat corrected milk for cows fed yeast culture. Control cows had numerically lower NDF digestibility. Distribution of fecal particles suggests more manure solids may pass the manure solids separator to the manure lagoon and therefore reduce the amount of manure solids collected with the separator. Yeast culture was shown to impact nutrient use by the animal and affect manure particle partition.

Modeling hydrogen sulfide emissions across the gas–liquid interface of an anaerobic swine waste treatment storage system

Hydrogen sulfide (H 2S) is a colorless gas emitted during decomposition of hog manure that produces an offensive “rotten egg” smell and is considered a toxic manure gas. In the southeastern United States, anaerobic waste treatment lagoons are widely used to store and treat hog excreta at commercial hog farms. Hydrogen sulfide is produced as manure decomposes anaerobically, resulting from the mineralization of organic sulfur compounds as well as the reduction of oxidized inorganic sulfur compounds by sulfur-reducing bacteria. The process of H 2S emissions from anaerobic waste treatment lagoons are investigated utilizing a two-film model with three different modeling approaches: Coupled Mass Transfer with Chemical Reactions Model with the assumption (1) pH remains constant in the liquid film (MTCR Model I) and (2) pH may change throughout the liquid film due to diffusion processes that occur within the film (MTCR Model II); and (3) a Mass Transfer Model which neglects chemical reactions (MTNCR Model) in the gas and liquid films. Results of model predictions are consistent with previous works, which show that flux is largely dependent on the physicochemical lagoon properties including sulfide concentration, pH, and lagoon temperature. Air temperature and low wind velocities (e.g., <3.25 m s −1) have negligible impact on flux. Results also indicate that flux values decrease with increased film thickness. The flux was primarily influenced by variations in the liquid film thickness, signifying that the H 2S flux is driven by liquid-phase parameters. Model results were compared with H 2S flux measurements made at a swine waste treatment storage lagoon in North Carolina using a dynamic emission flux chamber system in order to evaluate model accuracy in calculating lagoon H 2S emissions. The MTCR Model II predicted the highest increase in emission rates as aqueous sulfide concentration was increased. The MTNCR Model showed the highest dependence on pH. All three models showed good agreement in diurnal comparison with flux measurements; however, each model significantly over predicted the measured flux rates. The MTNCR Model estimates were closest to experimental values, predicting 3–35 times the actual measured values.

Microbial decolorization of spentwash: a review.

Spentwash is one of the most complex and cumbersome wastewater with very high BOD, COD and other organic and inorganic toxic constituents. It is dark brown colored and difficult to treat by normal biological process such as activated sludge or anaerobic lagooning. The color is due to the presence of melanoidins, caramels and other polymers. These compounds have anti oxidant properties which render them toxic to microorganisms. Spentwash disposal into the environment is hazardous and has a considerable pollution potential. It affects the aesthetic merit. Its decolorization by physical or chemical methods have been investigated and were found unsuitable. In the recent past, increasing attention has been directed towards utilizing microbial activity for decolorization of spentwash. This review reveals various groups of microorganisms which have potential in spentwash decolorization. The role of enzymes in decolorization and the microbial degradation of individual compounds imparting color to spentwash are also discussed.

Effects of Ionic Strength, Temperature, and pH on Degradation of Selected Antibiotics

Aqueous degradation rates, which include hydrolysis and epimerization, for chlortetracycline (CTC), oxytetracycline (OTC), tetracycline (TET), lincomycin (LNC), sulfachlorpyridazine (SCP), sulfadimethoxine (SDM), sulfathiazole (STZ), trimethoprim (TRM), and tylosin A (TYL) were studied as a function of ionic strength (0.0015, 0.050, or 0.084 mg/L as Na(2)HPO(4)), temperature (7, 22, and 35 degrees C), and pH (2, 5, 7, 9, and 11). Multiple linear regression revealed that ionic strength did not significantly affect (alpha = 0.05) degradation rates for all compounds, but temperature and pH affected rates for CTC, OTC, and TET significantly (alpha = 0.05). Degradation also was observed for TYL at pH 2 and 11. No significant degradation was observed for LNC, SCP, SDM, STZ, TRM, and TYL (pH 5, 7, and 9) under study conditions. Pseudo first-order rate constants, half-lives, and Arrhenius coefficients were calculated where appropriate. In general, hydrolysis rates for CTC, OTC, and TET increased as pH and temperature increased following Arrhenius relationships. Known degradation products were used to confirm that degradation had occurred, but these products were not quantified. Half-lives ranged from less than 6 h up to 9.7 wk for the tetracyclines and for TYL (pH 2 and 11), but no degradation of LIN, the sulfonamides, or TRM was observed during the study period. These results indicate that tetracyclines and TYL at pH 2 and 11 are prone to pH-mediated transformation and hydrolysis in some cases, but not the sulfonamides, LIN nor TRM are inclined to degrade under study conditions. This indicates that with the exception of CTC, OTC, and TET, pH-mediated reactions such as hydrolysis and epimerization are not likely removal mechanisms in surface water, anaerobic swine lagoons, wastewater, and ground water.

Opportunities and challenges of converting biogas from pig farms into renewable energy in developing countries in Asia - a Malaysian experience

To meet the rapid and increased demand for animal protein, intensive poultry and livestock farming units are growing quickly in many developing countries in Asia. To access the markets, such production units are primarily located in peri-urban areas where available land for manure treatment and/or recycling back to the soil is limited, thus leading to serious environmental pollution. Although poultry manure from these farms is readily used as organic fertiliser for the production of cash crops, pig manure is usually washed and discharged, with or without treatment, into nearby streams and rivers. Efficient treatment of wastewater from pig farms with limited land is very expensive as it normally requires some degree of artificial aeration. Although it has long been proven that the biogas produced from the anaerobic lagoons can be converted to reusable fuel for heating and/or the generation of electricity for the farm, the technology has not been well received by farmers because they have easy access to other cheap energy sources. However, due to the opportunity of gaining extra monetary return from carbon credit trading under the initiative of the Kyoto Protocol, many pig farmers are beginning to show interest in this technology. From a recent feasibility study conducted in Malaysia to assess the technical and economic viabilities of converting biogas from pig farms into electricity, the following challenges were identified: (i) the organic content of the wastewater generated from the pig farm was far below that required for the efficient production of biogas; (ii) the high costs required for the modification of the existing farm infrastructures and additional equipment made the project economically unattractive; (iii) the potential amount of electricity generated from such a project does not match the daily fluctuating electricity demand on-farm; (iv) current governmental policies and infrastructural supports to buy back the extra electricity generated from such a project are inadequate; (v) the misconception by farmers that recovery of biogas from an anaerobic lagoon will enhance the efficiency of wastewater treatment and thus improve the quality of their wastewater at endpoint to meet the governmental requirements for discharge; and (vi) the quantum sharing of the carbon fund by farmers and the carbon credit trading company.

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.

Equilibrium Sampling Used to Monitor Malodors in a Swine Waste Lagoon

The concentrations of malodorous compounds in a 0.4-ha anaerobic lagoon that received waste from approximately 2000 sows were monitored during the late summer to late fall of 2006 to gain insight into the factors influencing their concentrations. Selected malodorous compounds were measured by the use of equilibrium samplers consisting of submersible stir plates and stir bar sorbtive sampling with polydimethylsiloxane-coated magnetic stir bars. During the same period, air and water temperatures, suspended solids, total organic carbon and nitrogen content, and wastewater pH were recorded. Concentrations of malodorous compounds were higher at the surface of the lagoon than at the middle or bottom of the lagoon. Skatole concentration, for instance, averaged 54, 24, and 38 microg L(-1) near the surface, in the middle, and at the lowest sampling depths, respectively. While the lagoon was being pumped down during field application of wastewater, concentrations of malodorous compounds fluctuated widely, increased 16-fold as compared with the sampling period before pumping, and continued to increase as fall progressed and temperatures cooled. Suspended solids, volatile suspended solids, and total organic carbon increased near the bottom of the lagoon during this same period. The increases in the concentrations of malodorous compounds in the wastewater during the fall could have been due to a combination of several factors. These factors include reduced degradation by lagoon bacteria, less wind stripping of volatile compounds from the lagoon surface due to lowering of the lagoon surface after crop application, and/or reduced evaporation of malodorous compounds due to falling temperatures.

The Impact of Swine Lagoon Seepage on Shallow Groundwater Quality: Groundwater Remediation Through Lagoon Closure and Pumping

Anaerobic lagoons have been used extensively since about 1960 to temporarily store and partially treat livestock waste from concentrated animal production facilities. An earlier study characterized an unlined swine lagoon located in the Middle Coastal Plain of North Carolina and detected elevated mineral nitrogen concentrations (nitrogen as both nitrate and total ammoniacal nitrogen) 38 m down gradient from the lagoon. As this site was shown to be a potential source of nonpoint-source pollution, further study was needed to characterize the aerial extent of the seepage plume and remediate the contaminated groundwater. Hydrologic and water quality monitoring of the site was conducted from March 1999 to September 2004, a period during which the lagoon went from being semiactive to completely closed out. Analysis of data collected prior to lagoon closure indicated that seepage from the lagoon traveled to a nearby channelized stream. Total ammoniacal nitrogen (TAN = NH3-N + NH4-N) concentrations from monitoring wells installed between the lagoon and the channelized stream averaged 121 mg L-1 of TAN, with the highest concentrations exceeding 170 mg L-1. TAN concentrations in the stream 150 m down gradient from the lagoon ranged from 10 to 25 mg L-1. Monitoring of groundwater levels and subsurface water quality continued following the closure of the lagoon in March 2001, as well as through the installation of a groundwater pumping system and construction of a wetland that received and treated the contaminated groundwater. The average hydraulic gradient decreased from 0.0033 m m-1, prior to the activation of a groundwater pumping system (Mar. 1999 to Jan. 2000) to 0.0010 m m-1 after pumping was initiated (Sept. 2000 to Sept. 2004). Although the direction of groundwater flow was unaffected by the addition of the pumping system and water control structure, the average hydraulic gradient was reduced by 70%. Since the installation of the pumping system, approximately 17,900 m3 of subsurface water has been pumped, removing 1200 kg of TN from the groundwater plume. TAN concentrations steadily declined from 120 mg L-1 at the onset of pumping in September 2000 to less than 6 mg L-1 by September 2004.

Fate of estrogens and xenoestrogens in four sewage treatment plants with different technologies

The fate and removal of the estrogens 17beta-estradiol (E(2)), estrone (E(1)), and 17alpha-ethynylestradiol (EE(2)) and of the xenoestrogens bisphenol A (BPA), 4-tert-octylphenol (4-t-OP), 4-nonylphenol (4-NP), and nonylphenol mono- and diethoxylate (NPEO1 and NPEO2, respectively) were investigated in four South Australian sewage treatment plants (STPs; plants A-D) with different treatment technologies. The concentrations in the effluent from the two-year survey were similar to those reported in other studies. In the effluent, 4-NP, NPEO1, and NPEO2 had total concentrations up to 8 microg/L, which were much higher than those of BPA and 4-t-OP. Estrone had the highest concentrations among the three estrogens, ranging between 13.3 and 39.3 ng/L, whereas the concentrations for E(2) and EE(2) varied between 1.0 and 4.2 ng/L and between 0.1 and 1.3 ng/L, respectively. The removal rates for the estrogens and xenoestrogens were variable but consistent with the plant performance parameters (biochemical oxygen demand, suspended solids, and ammonia). Considering all the estrogenic compounds analyzed in the present study, plant D, with a series of anaerobic and aerobic lagoons, was the least efficient of the four STPs in the removal of these compounds. The removal rates for 4-NP, NPEO1, and NPEO2 within the plants were 92% for plant A, with conventional activated sludge treatment; 80% for plant B, with two oxidation ditches; 70% for plant C, with three bioreactors; and 64% for plant D, with 10 lagoons in series. Comparatively, the removal of estrogens was lower, with rates ranging between 47 and 68% for E(2) at the four plants. Both E(1) and EE(2) were more persistent during treatment, especially in plants C and D.

Process Model for Ammonia Volatilization from Anaerobic Swine Lagoons Incorporating Varying Wind Speeds and Gas Bubbling

Ammonia volatilization from treatment lagoons varies widely with the total ammonia concentration, pH, temperature, suspended solids, atmospheric ammonia concentration above the water surface, and wind speed. Ammonia emissions were estimated with a process-based mechanistic model integrating ammonia chemistry of the lagoon and interfacial transport characteristics between air and water. This improved model incorporated the effect of internal bubble production and continuously variable wind speed on ammonia volatilization measured at 10 m above the liquid surface (U10). Model simulations were compared to ammonia emission rates measured simultaneously at three contrasting lagoon scenarios: non-treated lagoon (13,633 kg ha-1 year-1), partially pre-treated manure using solid-liquid separation (3,699 kg ha-1 year-1), and treated manure using combined solid-liquid separation with nitrogen and phosphorus removal from the liquid (1,311 kg ha-1 year-1). The simulations only using average U10 with bubble enhancement or U10 distributions without bubble enhancement produced fluxes 42% and 44% below observed fluxes, respectively. However, the simulated fluxes using the U10 distributions along with bubble enhancement for the non-treated lagoon during warm seasons closely matched the observed fluxes (y = 1.04x, with R2 = 0.76). Ammonia emissions would be significantly underpredicted if bubbling-enhanced mass transport was not taken into account during warm seasons, as demonstrated by the improved process model and evidenced by the observed fluxes.

The possibility of palm oil mill effluent for biogas production

The world currently obtains its energy from the fossil fuels such as oil, natural gas and coal. However, the international crisis in the Middle East, rapid depletion of fossil fuel reserves as well as climate change have driven the world towards renewable energy sources which are abundant, untapped and environmentally friendly. Indonesia has abundant biomass resources generated from the agricultural industry particularly the large commodity, palm oil (Elaeis guiinensis Jacq.). The aims of the research were to (i) characterize palm oil mill effluent which will be used as source of biogas production, (ii) know the biotic and abiotic factors which effect POME substrate for biogas production by anaerobic digestion in bulk system. The results show that POME sludge generated from PT Pinago Utama mill is viscous, brown or grey and has an average total solid (TS) content of, 26.5-45.4, BOD is 23.5-29.3, COD is 49.0-63.6 and SS is 17.1-35.9 g/L, respectively. This substrate is a potential source of environmental pollutants. The biotic factors were kind and concentration of the inoculums, i.e. seed sludge of anaerobic lagoon II and 20% (w/v) respectively. Both physical and chemical factors such as pre-treated POME pH, pH neutralizer matter Ca (OH)2, temperature ≥40oC, agitation effect to increase biogas production, but in both coagulant concentration, FeCl2 were not.© 2008 Jurusan Biologi FMIPA UNS SurakartaKey words: characteristic of POME, biogas production, biotic and abiotic factors, batch system, laboratory scale