Pilot Study On Treatment Of Soybean Product Wastewater By Spiral Symmetric Flow Anaerobic Reactor

Soy products were popular among consumers because of their high protein content and reasonable amino acid composition,but they consumed a lot of clean water and produced a large amount of high-concentration organic wastewater during the processing of soy products.Bean processing wastewater is characterized by high chemical oxygen demand?COD?(generally 10000²0000 mg·L^-1)?high ammonia nitrogen values?high phosphorus content and low pH,no disposal of direct discharged into the receiving water body will cause serious pollution and affect the living environment and health of the residents directly.With the continuous expansion of the soybean processing industry,environmental pollution problems have attracted more and more attention.The spiral symmetrical flow anaerobic reactor?SSSAB?is a high-efficiency anaerobic reactor developed independently by our group.It has been successfully applied to different types of laboratory scale wastewater treatment,such as azo dyes,PVA wastewater and polyacrylate wastewater.In the treatment of practical soybean product processing wastewater,the pilot operation characteristics?spatial and temporal characteristics of granular sludge of SSSAB were investigated,,and drawed the following conclusions:1.SSSAB's pilot run characteristics?1?High performance:SSSAB was started within 30 days,and the maximum organic volume load?OLR?is 33.42 kg COD·?m³·d?^-1,the maximum volume removal rate?VRR?was 27.17 kg COD·?m³·d?^-1,and the corresponding COD removal rate was over 85%;The CH₄ yield was up to0.46⁰.53 L·gVSS^-1?the CH₄ content was 67.88%⁷3.77%?.?2?Stability:the VFA/ALK of the lower?middle and upper sections?C1?C2?C3,respectively?of SSSAB was 0.020⁰.031?0.019⁰.026?0.026⁰.036?far below the acidification threshold of 0.25?,and the pH was maintained at about 8.0,which was suitable for microbial growth.The overall COD removal rate,VRR and ammonia nitrogen increment of SSSAB had small CV average values?0.08?0.13 and 0.20,respectively,were weak variations?,and the reactor was in stable operation.?3?Bed removal efficiency has gradient distribution:the contribution of each section to the COD removal rate was C1?about 72.00%?>C2?about 13.00%?>C3?about 4.00%?,and the contribution to the increase of ammonia nitrogen was C1?42.15%⁴8.12%?>C2?1.97%⁷.12%?>C3?below 2.55%?;temperature as follows:each section C1?27.0³4.5??<C2?30.00³7.5??<C3?31.00³8.5??.2.Temporal and spatial characteristics of anaerobic granular sludge?1?Macroscopic characteristics:the average particle size of SSSAB decreased gradually from bottom to top?1.060mm?0.327mm and 0.197mm,respectively?,MLVSS showed a decreasing trend(48.056?13.190?13.505 kg·m^-3,respectively)and the porosity decreased gradually?83.27%?74.37%?70.11%,respectively?.Due to the macroscopic differences of granular sludge in the above sections,as a result,the sedimentation performance and mass transfer effect of granular sludge deteriorate gradually from bottom to top,and the metabolic efficiency decreases gradually.?2?Microscopic characteristics:the methane production activity of SSSAB from bottom to top?SMA?[118.13?744.05?783.13 ml CH₄·?gVSS·d?^-1,respectively]and microbial coenzyme F₄₂₀increased successively(0.220?0.630?0.690?mol·gVSS^-1,respectively),indicating that the methane production ability increased gradually from bottom to top.The PN/PS of TB-EPS decreased gradually?6.46?4.54 and 3.78,respectively?,and the relative content of Fe?5.66%?3.36%and1.38%,respectively?and Na?1.68%?1.42%and 0.62%,respectively?in the metal elements of granular sludge was high and decreased gradually,leading to the gradual deterioration of sedimentation performance and stability of granular sludge.?3?Bacterial community distribution:the dominant bacteria were filamentous bacteria in the lower segment,accompanied by a small amount of bacillus and coccus.The bacteria were mainly acid producing bacteria in this segment,and the acid producing stage of organic degradation was mainly completed in this segment.The dominant bacteria were cocci in the middle and upper segments?which may be mainly methanogens?and staphylococci?with a small amount of filamentous bacteria and bacilli?.