Treatment Of Pig Slurry Research Articles

Factors affecting Nitrogen Transformations and Related Nitrous Oxide Emissions from Aerobically Treated Piggery Slurry

A laboratory treatment system was designed to study the fate of nitrogen during aerobic treatment of pig slurry. Different aeration strategies, and more particularly the influence of residence time and aeration level, were manipulated. A series of six experiments was carried out to determine the nitrogen mass balance, including measurement of the gaseous nitrogen forms particularly ammonia and nitrous oxide. Further nitrogen transformations were examined during the subsequent anaerobic storage of aerated pig slurry at 7, 21 and 60 days. Aeration level and carbon content of raw slurry were identified as the main factors influencing nitrogen transformation during treatment. A high aeration level (2–4 mg O2/l) and/or low carbon content (biological oxygen demand of the raw slurry approximately 2 g/kg) resulted in nitrite accumulation (up to 33% of the total nitrogen content of the raw slurry) while a low level of aeration (redox potential=0 mVAg/AgCl) and high carbon content (biological oxygen demand of the raw slurry approximately 16 g/kg) led to simultaneous nitrification and denitrification which removed 66% of the total nitrogen in the raw slurry. Nitrous oxide emissions were observed in all treatments and represent up to 30% of the total nitrogen content of the raw slurry. Both nitrification and denitrification appear to be sources of nitrous oxide during the treatment. Further nitrous oxide emissions were recorded during subsequent storage, especially when the biological oxygen demand to NO−x-N ratio was lower than 1·3. However, during closed storage experiments, the nitrous oxide emitted was dissolved into the slurry and finally reduced to di-nitrogen after 60 days of storage.

Continuous Aerobic Treatment of Pig Slurry: Evaluation of Options based on Long-treatment Time and Two-stage Processing

Aerobic treatment can be very effective in dealing with a wide range of pollution problems from pig slurry, but it is often not popular due to the high energy costs implied. Improvement in the process performance and lower costs are key requirements in ensuring greater uptake of this technology. Two options in particular which may achieve this have been studied; long treatments of 20 d duration and two-stage processing. The long-treatment option offered major advantages when compared with a 2 d treatment process. The higher breakdown of organic matter, as indicated by the observed reduction in chemical oxygen demand (COD) of 43% compared with 30% for the short process was a significant improvement. This was achieved at a lower energy cost per m 3 of slurry processed. The improved efficiency of aeration was a consequence of the much lower aeration intensity (kgO 2 /m 3 h) required in the long-treatment reactor which enabled the use of high-efficiency diffusers. However, the reduced agitation also resulted in a tendency for particles to settle out, leading to the need for some additional mixing; this partly negated the energy saving from the efficient aeration process. Emissions of the air pollutant, nitrous oxide, accounted for 12% of the original nitrogen. Similar emissions also occurred in the two-stage and the 2 d treatment processes. A two-stage treatment comprising a 2 d reactor followed by a 20 d reactor achieved a COD reduction of 40%; this was no better than the 20 d reactor alone. Most of the microbial activity occurred in the first stage leaving the second stage under-utilized. The energy cost of operation of the two-stage process exceeded the sum of the two separate stages making this an expensive option with little tangible benefit over the single stage. By contrast, the long-treatment option, with lower running costs, emerges as an improvement over a short intensive treatment. Thus, the long-treatment strategy is recommended for aerobic treatment of pig slurry.

Solepur: A Soil Treatment Process for Pig Slurry with Subsequent Denitrification of Drainage Water

The soil purification capacity for treating pig slurry was evaluated over five years using a hydrologically isolated field treatment plant, the so-called “Solepur” process. This involves three operations: (1) overdosing the managed field with surplus slurry, (2) collecting and treating the nitrate rich leachate, (3) irrigating the final treated water over other fields. The facility consists of (1) a managed field (3280 mr2) which allows the total recovery of all the leachate water which percolates through growing ryegrass, Lolium perenne, to which the pig slurry is applied, (2) a storage-pump-reactor system for denitrification and (3) a non-managed field for completing treatment. The purpose of this study was to evaluate over a five year monitoring period, the feasibility and performances of such a process, and to determine the optimum operating conditions. From 1991 to 1995, 4931 mr3/ha of raw pig slurry was applied to the managed field, which represents a nominal load of 986 mr3 ha - 1 yr - 1. This process decreased the COD of pig slurry by 99·9% and removed 99·9% of phosphorus and approximately 90% of nitrogen. The Solepur’s final product is a limpid leachate containing a very low concentration of organic matter, but with relatively high nitrate levels resulting from oxidation of slurry nitrogen in soil. The extent of nitrification efficiency was satisfactorily demonstrated both through soil inorganic-N profiles and through continuous analysis of the leachate water leaving the overdosed field which shows nitrate concentration up to 1500 mg/l. Subsequently, the nitrogen removal from the nitrate rich leachate was achieved through batch denitrification sequences: raw pig slurry (which supplies carbon to support biological denitrification) is added to a volume of 150 to 250 mr3 of drainage water (representing a nitrogen load of 10 to 40 kg N) in the ratio 1:20 to 1:100 v/v. Parallel laboratory tests showed the influence of C/NO - 3-N ratio on the efficiency of nitrate nitrogen removal and demonstrated the feasibility of semi-continuous denitrification. It was confirmed that a C/NO - 3-N ratio of three is necessary to achieve a complete denitrification sequence. The results conclusively show that the Solepur process is a promising waste treatment system.

Evaluation of an Integrated System for Pig Slurry Treatment

A system for pig slurry treatment, where anaerobic digestion, nitrification and denitrification have been integrated in a unique process treatment, has been investigated. This configuration allowed both removal of Chemical Oxygen Demand (COD) and a decrease in nitrogen content. Strategies are reported to bring enough COD to the denitrification system. Results (90% reduction in COD, 99·8% reduction in NH4+-N and 98·8% reduction in NO3−N) show this process could be considered a good alternative to treat these wastes. © 1997 SCI.

A field treatment plant for pig slurry

The SOLEPUR process for the treatment of pig slurry, based on the treatment effect of the soil, was developed in France to explore the notion that a simple biobarrier approach may be a potential efficient solution to the large accumulation of liquid animal wastes residues. The unit consists of (i) a managed field (3280 m2) which allows the total recovery of all the leachate water which percolates through growing ryegrass (Lolium perenne), to which the pig slurry is applied, (ii) a system of storage-pump-reactor for denitrification and (iii) a non-managed field for completing treatment. The process involves three operations: (1) overdosing the managed field with surplus slurry (about 1000 m3 pig slurry/ha.year applied from 1991 to 1994), (2) collecting and treating the nitrate-rich leachate and (3) irrigating the final treated water over other fields. This process decreased COD of pig slurry by 99.9 % and removed 99.9 % of phosphorus and approximately 80 % of nitrogen. The remaining nitrogen was oxidized in the soil into nitrate and leached out in the drainage water. The process of denitrification was selected to remove nitrate from the leachate and raw pig slurry was used as an external carbon source.

A field treatment plant for pig slurry

The SOLEPUR process for the treatment of pig slurry, based on the treatment effect of the soil, was developed in France to explore the notion that a simple biobarrier approach may be a potential efficient solution to the large accumulation of liquid animal wastes residues. The unit consists of (i) a managed field (3280 m2) which allows the total recovery of all the leachate water which percolates through growing ryegrass (Lolium perenne), to which the pig slurry is applied, (ii) a system of storage-pump-reactor for denitrification and (iii) a non-managed field for completing treatment. The process involves three operations: (1) overdosing the managed field with surplus slurry (about 1000 m3 pig slurry/ha.year applied from 1991 to 1994), (2) collecting and treating the nitrate-rich leachate and (3) irrigating the final treated water over other fields. This process decreased COD of pig slurry by 99.9 % and removed 99.9 % of phosphorus and approximately 80 % of nitrogen. The remaining nitrogen was oxidized in the soil into nitrate and leached out in the drainage water. The process of denitrification was selected to remove nitrate from the leachate and raw pig slurry was used as an external carbon source.

The origin of insights in chemical engineering: Planned and unplanned research

In chemical engineering, research workers have always tried to relate their work to industrial needs. In all countries and in all subjects, there is now pressure from governments to do useful research. It is therefore helpful to review the origins of research in chemical engineering: do the best topics originate from planning for the greatest good of the greatest number, or do they happen adventitiously from accidental combinations of circumstances leading to bright ideas? The latter appears to be more effective, both for good research and for the greater good. Close contact with industry is stimulating. Research and teaching are mutually beneficial. These general conclusions will be illustrated by reference to the writer's experience with the following research topics. To demonstrate the importance of long time scales, the starting date is given for each topic. 1. o 2. (1) The study of bubbles in fluidised beds began in 1956, via a teaching experiment and undergraduate projects with minimal planning and negligible funding. 3. (2) Work on coal combustion in a fluidised bed began in 1967, via a long-term plan of the British National Coal Board. The plan was subsequently mutilated by the vagaries of energy prices, but the research and some practical applications endure. 4. (3) Work on bubble columns began in 1965 with the need to understand oxidation reactors. There was later stimulus from the ICI Pruteen process; the process was subsequently an economic failure, but the research results have found wide use. 5. (4) Work on the velocity of sound in fluidised beds began in 1988, an offshoot from another project: the work was highly successful but, being an unplanned adjunct, was frowned on by the funding agency. 6. (5) A project on treatment of pig slurry led, surprisingly, to work on rupture of thin liquid films (1990), now of interest to biotechnologists concerned with cell damage. 7. (6) NMR research in Chemical Engineering began in Cambridge by accident in 1989: a government agency happened, by maladroit planning, to have an unspent balance. 8. (7) Cold extrusion of chocolate is a recent, industrially relevant, bright idea of Dr Mackley, arising from the propinquity of (a) his work on polymer extrusion and (b) work on food processing initiated via the “New Blood Scheme” in the 1980s. The conclusion is that it is crucial to be able to seize opportunities as they occur. No doubt there must be planning—especially as research becomes more expensive—but the keynote should be flexibility especially because industrial objectives are subject to rapid and unpredictable change.

Composition andin saccoDegradability of Variously Treated Pig Slurry Solids before and after Anaerobic Digestion

Abstract Flachowsky, G., Richter, G. H. and Löhnert, H.J. 1995. Composition and in sacco degradability of variously treated pig slurry solids before and after anaerobic digestion. J. AppL Anim. Res., 7: 161–168. The fresh and digested pig slurry was separated into a solid and liquid phase by centrifugation. The solids of the slurry (fresh and digested) were treated with urea and I or NaOH and used for the estimation of chemical composition and dry matter degradability (DMD). Anaerobic digestion did not significantly influence chemical composition except iron content. The DMD of anaerobically—digested solids was significantly lower (34.8%) than that of the influent material (48%). Chemical treatment of solids from the influent increased DMD from 48.0 to 54.5 (2% urea), 60.2 (2% NaOH) and 62.0% (2% urea and NaOH each); DMD of effluent was increased from 34.8 to 46.4, 49.4 and 51.3%, respectively. Pig slurry solids from the effluent of anaerobic digesters contain low energy for ruminants and should primarily be used as manure.

Modelling the Performance of a Non-steady State Continuous Aeration Plant for the Treatment of Pig Slurry

The performance of a non-steady state aeration process for treating pig slurry has been modelled, using a combination of engineering and microbiological concepts. Performance was defined in terms of COD reduction but estimation of temperature was also necessary both as an intermediate step in estimating the COD/BOD level, and also to identify conditions which fell outside the optimal range of mesophilic activity. Two models are presented and referred to as RM (running mean) and IS (incremental step). The first model used steady-state equations for heat balances and COD predictions with input values averaged over preceding days. The second model used a combination of a microbial model for population and substrate (BOD) level and a heat flow imbalance to predict temperature changes. Model constants were established using data on temperature and COD reduction from a 2000 ha farm scale trial in which operating conditions were varied throughout. The models were then tested, on data from a 1000 ha trial carried out a year later: both followed the changing COD and temperature of the treated slurry with predicted values within 20% of those measured. Despite its greater sophistication, the IS model provided no improvement in prediction over the simpler RM model. This may be the consequence of imprecise and incomplete data, and highlights the limitation of a more rigorous approach to a complex microbial system that exists in a slurry treatment plant.

Simultaneous high-biomass protein production and nutrient removal using Spirulina maxima in sea water supplemented with anaerobic effluents

Maximum protein accumulation (71%, w/w) and nutrient removal by a mutant strain of Spirulina maxima growing on sea water supplemented with anaerobically treated pig slurry was achieved at 30°C with constant illumination (60 to 70 μEm(-2)s(-1)), using a flow rate of 14.5 cm s(-1) (20 rev. min(-1) of a paddle wheel). Total phosphates were decreased by 99% and all ammonia-N was removed under these conditions.

Emissions of nitrogen oxide gases during aerobic treatment of animal slurries

Abstract Quantities of nitrous oxide, N 2 O, an important greenhouse gas, were found in the effluent gases from controlled continuous aerobic treatment of pig slurry. Where nitrifying-denitrifying conditions were encouraged (4-day treatment time and aeration to a redox potential of −50 mV E cal ), concentrations of this gas at times exceeded 1500 ppm and accounted for 19% of the nitrogen lost from the slurry. Smaller concentrations of the gas (170 ppm) were found during short treatments (1·5 days) where nitrifying activity would not be expected; partial nitrification is a possible explanation. Quantities of nitric oxide (NO) (up to 100 ppm), and even small amounts of NO 2 , were also found, suggesting these previously unquantified nitrogen transformation routes in the traditional nitrogen cycle exist in aerobic treatment processes.

A mathematical model of bacterial growth in aerated pig slurry during anaerobic storage

Experiments are being conducted on the aerobic treatment of pig slurry and its subsequent anaerobic storage intended to determine lower cost methods of odour control. One series, using batch aeration for 3 to 9 days followed by storage for one year, has been completed. This paper describes a model of the storage phase. A model of bacterial growth based on Monod kinetics is used. Two forms of inhibition are included to improve the agreement with the experimental data. The model successfully describes many features found in the experiments, though others, such as the very rapid changes in volatile fatty and concentrations observed in some of the experiments, do not appear. The available literature on the modelling and microbiology of waste treatment offers no satisfactory explanations of these observations. At present the model can be applied only to the situations considered here, but it could provide the basis for further development.

Rumen dry Matter Degradability of Various Pig Faeces and Chemically Treated Pig Slurry Solids

Rumen dry Matter Degradability of Various Pig Faeces and Chemically Treated Pig Slurry Solids

Traitement aérobie du lisier de porc: aspects microbiens

During the treatment of raw pig slurry by batch aerobic fermentation, the presence of surfaces for bacterial attachment resulted in a 1,000-fold increase in the microbial population. In the absence of such surfaces, a 65% reduction of the chemical oxygen demand (COD) of the manure was obtained after 168 h of aeration, whereas a value of 90% was observed in their presence. In the early stages of the treatment, during which the redox potential passed from a value characteristic of anaerobic conditions (-305 mV) to a stable value typical of aerobic conditions (+125 mV) some 120 h later, an amylolytic population dominated by Gram-negative bacteria (chiefly Acinetobacter calcoaceticus) developed; this was followed by a phase in which a proteolytic population tended to become dominant. Populations of some potentially pathogenic bacterial strains characteristic of the porcine intestinal flora declined noticeably during the treatment.

The photosynthetic treatment of pig slurry in temperate climatic conditions: A pilot-plant study

Results are presented for a pilot-plant scale study of algal culture in the liquid phase of pig slurry under temperate climatic conditions (latitude 54° 26′ N, longitude 6°06′ W). The pilot-plant was operated as a continuous culture over a two-year period and biomass production and nutrient stripping were intensively monitored. The two culture tanks were of raceway design each containing 2200 litres with a surface area of 11·1m 2. The inoculated alga was Chlorella vulgaris (CCAP strain No. 211/1e). Retention times in the culture were set by the rate of addition of slurry which was prepared by screening, flocculation and dilution 1:9 with water to reduce the suspended solids content to 0·2%. Short-term algal productivities, corrected for slurry solids input, were between 7·65 and 32·9 g DM m −2 day −1 at a retention time of 4·5 days. The mean longterm productivity was 18·1 g DM m −2 day −1. The results suggested a 153 day growing season with a total algal productivity of 25·65 t ha −1. Phosphorus removal ranged from 42 to 89% and that for nitrogen ranged from 54 to 98%, BOD 5 removal was approximately 98%. Differences between laboratory and outdoor pilot-plant cluture work are discussed and the importance of light as a limiting factor is considered.

Monitoring anaerobic digesters on farms

There are 15 anaerobic digesters installed on farms in the U.K. and these were largely stimulated by the opportunity to produce energy coupled with a reduction in slurry odour. A monitoring programme was developed in 1980 to evaluate the average performance of farm plants in terms of net energy production under practical operating conditions. The aim was also to determine the effects of digestion on slurry with regard to pollution reduction and fertilizer value. This paper reports data gathered from one pilot-scale and two full-scale digesters, treating pig slurry, and from one full-scale digester treating dairy cattle slurry. Monitoring showed on full-scale plants, that pig slurry achieved a specific gross biogas production of 0·5 (m 3 biogas)(m 3 digester volume) −1 d −1 and for dairy cow slurry 0·8 (m 3 biogas) (m 3 digester volume) −1 d −1. A pilot plant operating on stored separated pig slurry at a retention time of 8·3 d produced 1·8 (m 3 biogas)(m 3 digester volume) −1 d −1. The biogas yield from the total solids (TS) in pig slurry fed ranged from 0·28 to 0·37 m 3 biogas/kg TS fed. The yield from dairy cow slurry was 0·12 m 3 biogas/kg TS fed. Digester management was found to be important for the successful steady-state operation of digesters on farms. Digester feed solid concentration and feed age were found to influence specific gross biogas production.

Plant growth inhibitory activity of extracts of raw and treated pig slurry

AbstractStrong acid extracts from raw and treated pig slurries were highly inhibitory to the germination and root growth of barley and wheat. While the activity of the extracts reflected the level of phenolic acids therein, the possibility of other substances contributing to this activity cannot be excluded. Tests with pure compounds showed that certain individual phenolic acids identified in pig slurries inhibited germination and root growth but at higher concentrations than previously reported. Of the treatment systems studied, aeration of pig slurry was the most effective in removing the inhibitory activity associated with extracts.

Phenolic acids in pig slurry subjected to various treatment processes

AbstractThin‐layer chromatography of extracts of raw and treated pig slurries revealed the presence of phenolic acids. The number of phenolic acids present in raw slurry was reduced considerably by aeration and, to a smaller extent, by treatment with hydrogen peroxide; anaerobic storage and digestion proved ineffective for the removal of phenolic acids from pig slurry.

Investigations on the use of treated pig slurry in recirculating water culture of tomatoes

The use of liquors from treated pig slurry in the hydroculture of tomato ( Lycopersicon esculentum, cv. Sonato) is described and the utilisation of major nutrients and fruit yields is reported. While such liquors require amendment with potassium, magnesium, and certain trace elements, they can be used as a complete source of nitrogen and phosphorus to produce limited quantities of fruit of satisfactory quality. However, there is a need to control the accumulation of sodium ion in the nutrient solution and the plants were affected by unidentified materials present in one batch of treated pig slurry liquor.

Investigations on the aerobic treatment of pig slurry

Investigations with a three-stage laboratory aerobic treatment system for pig slurry are described. The system is effective for eliminating odour, and after solids separation gives a stable, odourless liquor. Considerable nitrogen losses take place during the treatment process.