Wastewater Treatment Of Nitrite Pulp And Paper Making By Coagulation-Air Flotation-Anaerobic/aerobic Process

There are many organics, suspended solids, ammonia nitrogen and some otherpollutants which are complex and high concentrated in the ammonium sulfite methodpaper mill wastewater. The "coagulation-air flotation-A/O"component technology treatingpaper-making wastewater by the ammonium sulfite method was studied in this paper. Thepurifying effect of coagulants was studied; Optimal coagulants and the dosage wereoptimized and decided, technology were optimized. It considered the removalcharacteristics of the system and it's units toward organic matter, nitrogen and phosphorusrespectively. Then researched on the optimization of the control parameters.The experiment of coagulation sedimentation using aluminium sulphate, PAC andPES, which showed that PAC is the most reliable option. When the coagulant dosage was0.8mg/L, the removal rate of COD_Cr could achieve 44.6%. The results of coagulation-airflotation under the experiment conditions showed that when the pH value was 7～8, theinfluent concentration of COD_Cr and SS were 1760～2230mg/L and 550～650mg/L,respectively, the average effluent COD_Cr and SS were 1098mg/L and 58.3mg/L,respectively, the removal rate of COD_Cr and SS could respectively achieved 45.1% and90.4%.There are fibers in the both anoxic and aerobic reactors of A/O technology. In thisexperiment, start-up is performed under continuous inflow condition and the volumeloading was increased gradually and the aeration mode was controlled in different stage;when the quantity of influent is 800m³/d, the removal rate of COD_Cr and ammonia nitrogencould respectively achieve 86.8% and 87.7%. It fulfilled biofilm cultivate andmicroorganisms culture. During improving loading stage, the dissolved oxygen of effluentwas maintained in 3-4mg/L, the reflux ratio was 2 and the influent load was increasedgradually according to the running effect. After 83 days, the quantity of influent increasedfrom 800 m³/d to 3000m³/d, HRT decreased from 18h to 6h, the influent concentration ofCOD_Cr and ammonia nitrogen was 986-1184mg/L and 82.8-98.5mg/L, respectively. Theeffluent average concentration of COD_Cr and ammonia nitrogen was 207mg/L and 12.5mg/L, respectively. The removal rate of COD_Cr and ammonia nitrogen could respectivelyachieve 80.8% and 85.7%, COD_Cr and ammonia nitrogen loading respectively achieve1.5kg/(m³Â·d) and 0.12kg/(m³Â·d). The experimental results of components runningdemonstrated that under the controlled conditions, both anoxic and oxic reactors havenitrification,denitrification and favorable organics treatment effects.The investigation of the optimum operation indicated that for ammonium sulfitemethod paper mill wastewater, the component technology has the optimal running effectwith the quantity of influent 3000m³/d, HRT 2, the dissolved oxygen 4mg/L, the removalrate of COD_Cr and ammonia nitrogen could respectively achieve 80.8% and 85.7%; theaverage effluent of COD_cr and ammonia nitrogen was 210mg/l and 13.4mg/l.