Application In Engineering Study On Coagulation-Air Flotation+Hydrolysis Acidification+CASS Process In Treating Concentrated Apple Juice Processing Wastewater

Concentrated apple juice processing is a potential growth industry, which has made great contributions to China's national economy, but it also caused serious environmental pollution problems, especially in water pollution. Concentrated apple juice wastewater is a high concentration organic wastewater, which has strong viscosity, low PH, high COD and high SS. If a lot of apple juice wastewater is discharged directly into water bodies without treatment, it will affect the aquatic ecosystem, leading to serious deterioration of surrounding water environment. At present the apple juice wastewater relative treatment technology has been few reported abroad, while mature and reliable domestic wastewater treatment process has also been rarely reported. So to find such a practical purification of wastewater treatment process has become a current problem of the environmental protection technology field at home and abroad.This issue bases on the latest research results apple juice wastewater treatment technology at home and abroad. Through the basis of widely looking up relevant information and analyzing the problems of the actual process, combining experimental study with practical engineering, it is proposed that using "Coagulation-Air Flotation+Hydrolysis Acidification+CASS" combined process treats concentrated apple juice wastewater of Henyuan Juice Co., Ltd., Sichuan. The research is focus on finding out optimum run-time process parameters and control conditions by the experimental study and the debugging project run, analyzing the removal result and the variation regulations of COD, SS, etc. The specific result of experimental study and the project debugging run as follows:(1) In Coagulation-Air Flotation unit test, it is defined that the best dosage of coagulant PAC is 50mg/L, the optimum flotation time is 20min and the best flotation pressure is 4kg/cm2. Under this conditions, the removal rate of COD and SS are about 45% and 65%, which is good for both the removal efficiency of COD and SS and reducing energy consumption.(2) The pool of hydrolysis acidification is started with low-load method. The inoculation sludge reached a relatively stable operating state after 20 days cultivation and domestication. The experimental study shows that the best HRT of hydrolysis acidification is 10 hours. In this condition, the removal rate of COD and SS are about 45% and 75%. When the PH and COD of the entering wastewater are about 5.0-8.0,2000-3000mg/L, the pool of hydrolysis acidification remains relatively stable operating state, which proves that it has a certain ability to resist impact load.(3) The activated sludge of cultivation and domestication can be finished in CASS biochemical pool in about two weeks. After that the sludge concentration and settlement ratio reach a relatively stable state. The MLSS is stable at about 5000mg/L, and the SV30 is stable at 26%-33% or so. After the successful start of CASS biochemical pool, the entering wastewater conditions are that the COD concentration is 1200mg/L or so, PH is 6.0 to 7.0 range, the water temperature is around 21℃, the adding nutrients ratio is C:N:P=500:5:1. In this condition, the best processing cycle of CASS is 8 hours-water aeration 1h, aeration 4h, precipitation 1h, decanter 2h. Meanwhile, the removal rate of COD on CASS process is about 91%. The experimental results also show:when the wastewater temperature of entering CASS biochemical pool is 19℃-24℃, the PH is 5.5-7.5 range, the removal rate of COD and SS remains relatively stable state of operation.(4) Though debugging run to apple juice wastewater treatment combining process system, it indicates:Coagulation-Air Flotation unit plays an important role on the removal of COD and SS, and the removal rate of COD and SS are 44.2%and 48.6%. The removal rate of COD and SS are 12.4%and 28.0% by rotor grid. The removal rate of COD and SS in the hydrolysis acidification pool are 21.3% and 19.0%. The COD of the CASS biochemical pool is mostly dissolved organic matter, the removal rate of which is 20.0%. The treated effluent of concentrated apple juice wastewater can reach theⅠ-class criteria specified in Integrated Wastewater Discharge Standdard (GB8978-1996).(5) Treated effluent is reused after filtration and disinfection process, saving water resources.The subject comes from actual project of concentrated apple juice wastewater treatment, which has a highly targeted. The engineering practice proves that "Coagulation-Air Flotation +Hydrolysis Acidification+CASS" combined process is an efficient, economical, practical treatment technology of apple juice wastewater. The results propose the reasonable technology line and run experience for the type of apple juice wastewater treatment, which has important reference value and guiding significance.