Study On The Treatment Of Low Concentration Wastewater From Livestock Farms

With the rapid development of intensive livestock raising, livestock pollutants became the third largest pollution following industrial pollution and domestic pollution.If not be rationally treated,they would severely affect the quality of air,water,soil and trigger a series of other problems.These farms generated a lot of organic wastewater with water flushing the manure and solid-liquid separation. Now there’re some problems such as the seasonal effects, the larger area, run complex or high cost in wastewater treatment methods.For seeking a better wastewater treatment method, this paper took the large-volume, low-concentration wastewater not reaching national standards as the object, and carried out following studies:It’s significant to study on deodorizing swine urine which was the main composition of poultry wastewater was an important source of odor. With strong oxidant H2O2removing its odor, the results showed that0.42%H2O2had good deodorizing effect on the fresh swine urine which was near neutral. The long placed urine was alkaline with slightly larger dosage of H2O2to deodorize.Making use of cyanobacteria absorbing nitrogen and phosphorus to treat wastewater, the results indicated that for40～56d cyanobacteria removed55%-95%TP and73%～96%TN in swine urine of COD417.1～173.8mg/L, TN215.74～89.89mg/L, TP14.81～6.17mg/L and in biogas slurry of COD675～337.5mg/L, TN279.63～139.82mg/L, TP8.63～4.32mg/L under natural light culture. The higher concentration of wastewater, the longer the growing adaptation of cyanobacteria and the steady stage of TP removal rate.The lower concentration, the higher the TP removal rate. pH7-8of wastewater had no effect on cyanobacteria removing of TN and TP. If wastewater was in below COD400mg/L, TN180mg/L, TP12.3mg/L, It cost cyanobacteria40～56d to make TN, TP of wastewater reach national standards with average temperature above15℃.Not affected by the seasons not liking cyanobacteria, electrodialysis(ED) made wastewater divide into concentrated water and fresh water. It’s hoped to reduce the area of the existing wastewater treatment and make fresh water become wash water of poultry beds.The results showed that the odor and about50%of TP, COD were reduced by flocculant in wastewater pretreatment. It’s good to separate NH3-N and COD with ED, which made both of them meet national standards easier, especially NH3-N. It could be applied to the exit of grit chamber with wastewater COD950mg/L, NH3-N373mg/L, TP163mg/L, which could produce fresh water accounting for88.5%of the total volume. NH3-N, COD of fresh water reached the national standards with the cost of CNY3.2-3.6. However, TP was low in concentrated water but high in the fresh.Two phosphate-accumulating organisms NM-18and NM-21were isolated from the sludge of a contaminated river. Two strains had been in the state of accumulating phosphorus in different media under30℃,180r/min condition. The maximum phosphorus removal rates of them were88%and56%at120h in phosphorus-rich medium. They’re73%and63%respectively at96h in LB medium. NM-18and NM-21were preliminarily identified as Acinetobacter sp. and Aeromonas sp., according to their physiological and biochemical characteristics and the analysis of16S rRNA gene sequences. NM-18can grow well in25～7℃and initial pH5.0～9.0.When NM-18, NM-21and mixed two strains dealt with aeration tank wastewater under30℃,180r/min condition, their phosphorus removal rates were62%,64%and69%respectively at48h. Under120hrs continuous aeration and120hrs intermittent aeration conditions in self-developed reactor, the highest phosphorus removal rates of NM-18treating diluting actual mixed wastewater at24h were17%and56%respectively.