Pilot Study On Disinfection Methods Of Treated Effluent From Swine Farm

At present，water consumption of animal feeding operations is high, thus the amount of wastewaterproduced in AFOs is big. When the swine waste water is recycled or discharged, it will bring the hugerisk in biology. In this thesis, three disinfection methods including physical and chemical methods wereused to treat the swine wastewater, for each method, several factors that affect the disinfection effectswere tested. These factors include the transmittance of the wastewater, the hydraulic retention time, thewater depth, the ultrasonic frequency, or the ozone concentration. At the last part of the thesis, the costsof these disinfection methods were assessed to provide reference for related studies. The followings arethe main conclusions of this study:1. In the experiment, the number of the total bacteria is at109（CFU/L）,while the total coliform is at108（CFU/L）and the number of the fecal coliform is at107/L. The number of the fecal coliform isone thousand times more than the standard number according to the Discharge standard ofpollutants for livestock and poultry breeding.2. In the experiment, flocculation was used for pre-treatment. When using ultraviolet lamp of395μW/cm2and0.69%transmittance of the supernatant with fitting depth of2cm and HRT15min,the number of fecal coliform in the effluent was less than3/L which is the detection limit, reachingrelated national standards.3. Flocculation was used as the pre-treatment. The number of fecal coliform in the effluent decreasedfrom8.1×106/L to104/L after ultrasonic disinfection with20kHz frequency and60min HRT or20+40kHz frequency and30min HRT. The disinfection effect reached the current nationalstandards.4. Flocculation was employed for pre-treatment The effluent after flocculation was mixed with ozoneby ejector and booster. When the ozone dosage was up to20g in one ton of sewage, the number offecal coliform decreased from1.2×107/L to104/L. The disinfection effect reached the currentnational standards.5. The investment and operating costs were calculated via the pilot-scale program. In the program, theamount of the water produced was set at the50t/d. By the analysis, the ultraviolet which theinvestment and operating costs were low was recognized as the better technology. The investmentcost of the ultraviolet is38,000RMB, and the operating cost is1.4RMB for one ton of wastewater.According to the results, it was concluded that the ultraviolet disinfection method was relativelygood among the three disinfection methods when the swine wastewater meet the ultraviolettransmittance requirement. The ultraviolet disinfection method can operate with low cost, while the costof the ultrasonic disinfection is high and works with loud noise. Therefore the ultrasonic disinfectionmethod is not recommended. For the ozone sterilization method, it requires large areas for installationof the deep aeration tank, and its management is complicated. The extent to which the wastewater is mixed with ozone highly affect the disinfection effects，which is the key technology of this method,hence it need to be studied intensively.