Study On Wastewater Treatment Plant Upgrading Of A Straw Pulp And Papermaking Enterprise

With the Discharge standard of Water Pollutants for Pulp and Paper Industry more and more strict,it is urgent for many enterprises of papermaking industry to upgrade their wastewater treatment plants.Combined with the actual upgrading and reconstruction of a pulp and paper-making plant in Shandong,the application of A/O process and active sand filter was studied.In the midcourse wastewater upgrading and reconstruction project,the original aeration tank was changed to A/O process,and the main operating parameters of the process were optimized.The optimal operation conditions were as follows:HRT?A?:HRT?O?=2:3,nitrate recycling ratios=300%,temperature?20^o C,and ammonium nitrogen concentration of influent?40 mg/L.After upgrading and reconstruction of the biological treatment process,removal efficiency of nitrogen was improved significantly,the removal efficiency of COD,TN and NH₃-N were 83%,96%and 91%,respectly.In the biochemical treatment system,the materials of the aeration membrane were compared and selected.The results showed that the oxygen transfer coefficient of silica gel membrane aerator was better than ethylene propylene diene monomer membrane aerator.The influence factors which influenced oxygen transfer process of gas-liquid had been investigated.Results showed that the oxygen transfer coefficient(K_La)increased with the air flow rate increasing;K_La increased significantly as the concentration of NaCl rised from 0 mg/L to 6000 mg/L,K_La kept stable when the concentration of NaCl was above 6000 mg/L.When the concentration of surfactant?sodium dodecyl benzene sulfate?was adjusted from 0 to 20 mg/L,K_La decreased firstly then increased slightly.In the paper machine white water treatment project,the active sand filter applied to advanced treatment of the paper machine white water was studied.Firstly,.The influence factors on sand-lift system of active sand filter have been investigated.The results showed that with the air flow increased,the amount of lifted water and sand both have a trend of increasing first and then deceasing;the diameter of riser pipe mainly determines the maximum amount of lifted sand;Under the same condition,with the increase of submergence ratio of riser pipe,the amount of lifted water and sand both increased.In the study,the optimal operating parameters of activated sand filter were studied.The results showed that the removal efficiency of SS decreased gradually with the increasing of the filtering rate,and the removal efficiency of SS was about 50%when the filtering rate was less than 5.4 m/h;With sand recycling velocity increasing,the removal efficiency of SS increased firstly then decreased;The removal efficiency of SS increased significantly as filter thickness rised from 0 to 40 cm,and increased slowly when filter thickness was above 40 cm.