Pollution Investigation And Treatment Of Swine Wastewater From Small Scale Pig Farms In Beijing Suburbs

Livestock pollution has become the third source of pollution after industrial and domestic pollution. Developing economic and efficient farm wastewater treatment technology is the focus of current research. In this paper, pollution characteristics of effluent were investigated in small pig farms in Beijing suburb, and investigate wastewater treatment technology. This study employed a single anaerobic baffled reactor(ABR) to treat simulated swine wastewater. Start-up procedure, removal efficiency of pollutant and the operation characteristic were explored. The feasibility and optimization of these reactors were determined too. The impacts of dissolved oxygen level and C/N ratios on COD and nitrogen removal efficiencies in a sequential batch reactor were studied. Based on the object of swine wastewater, this study focused on removal efficiency of pollutant using the combined technique of ABR and SBR. The results were as follows:The results of the survey of 21 pig farms in Beijing suburbs showed that:the water quality of effluent greatly varied with farms. COD, BOD, NH3-N, TN, TP and SS concentration range were 3614-15310,1600-8180,164.5-1375.5,332.4-2617.2,21.3-254.5 and 358-3800 mg/L. Concentration range of copper and zinc were not detected to 5.875 mg/L and 0.172 to 23.434 mg/L, each with 47.6% and 52.4% of samples exceeded emission limits, which is stuplated by emission standards of livestock industry for comment. Total bacteria, fecal coliforms, ascaris eggs concentration range were 1.28×105-1.92×107 CFU/ml,3.6×105-8.8×107 MPN/L and 0-8 a/L. Through research and investigations, treatment were generally complete for large-scale pig farms.Small pig farms or scattered farms,just set up anaerobic treatment unit or not.The simulant swine wastewater was used as inflow treated by ABR which has been seeded with anaerobic granular sludge in advance. The start-up of ABR was made under the conditions of 33±1 ℃, and the start-up mode were low load and low increase. The start-up time lasted 61 days and the final removal efficiencies of COD, NH3-N and TP were 93%,21% and 32%. Removal efficiencies of COD, NH3-N reduced with HRT shortening gradually. Temperature changes did not show obvious influence on removal efficiencies of ABR. During ABR start-up, the median diameter of granular sludge increased from 0.53mm to 0.59-1.12 mm. Mature granular sludge in ABR showed hydrogel structure characteristic, structure of mature granular sludge was looser than seed sludge.The simulant anaerobically digested effluent was used as inflow treated by SBR.The results showed that when NH4+-N is 300 mg/L, COD is 800 mg/L, controlling temperature within 24-26 ℃, adding 1.13 g carbon, NH4+-N removal efficiency increased as DO level increased. The removal rate of NH4+-N were 88% and 96% by setting dissolved oxygen levels at 2.0,4.0 mg/L.However, the removal rate of TN decreased as DO level increased. The removal rate of TN were 86% and 78% by setting dissolved oxygen levels at 2.0,4.0 mg/L.While the DO were 2.0 mg/L and 4.0 mg/L, NO2--N accumulation rates are 49% and 54%, respectively. It may occurred the shortcut nitrification-denitrification under the condition of low dissolved oxygen. The phenomenon of simultaneous nitrification and denitrification(SND) was more obvious when low DO was applied and the C/N ratio was about 6. While the DO were 2.0 mg/L and the C/N ratio was about 6, SND rates were 94.91% after 4 hours of aeration. COD removal efficiency increased as C/N increased. Improving the C/N was beneficial to the removal of ammonia nitrogen and total nitrogen.Swine wastewater treatment was studied by ABR-SBR combined process, and the operating characteristic of the combination process was investigated. During the operation of the ABR-SBR combined process, COD removal rate maintained at 97.6%. The removal rate of NH3-N and TP reached 95.3% and 59.5%.On the basis of experimental results and reference literature, combined with characteristics of livestock wastewater, processing 300 t of piggery wastewater treatment engineering process was designed. Combined with the economic benefit, social benefit and environmental benefit, the main equipment was the solid-liquid separation pretreatment-ABR-SBR-Chemi-Denipho process.