Application Research On Treatment Of Dyeing Wastewater By Combined Process Of Biologicalaerated Filter And Reverse Osmosis

Printing and dyeing wastewater has the characteristics of high alkalinity,high temperature,complex composition and poor biodegradability,which could severely damage receiving water environment if it discharged into water without treatment.At present,the treatment of printing and dyeing wastewater mainly includes pretreatment,biochemical treatment and advanced treatment.During each treatment choose the suitable technology according to the quality of influent water.However,a few research were reported on the treatment of printing and dyeing wastewater by the integrated technique of biological aerated filter?BAF?and reverse osmosis?RO?.In this paper,the integrated technique of BAF and RO was used to treat the dyeing wastewater.The operation of two stages and the treatment efficiency were studied.First of all,the BAF was started by inoculating biofilm to treat the simulated methylene blue wastewater.After the operation was stable,the operation conditions of BAF were optimized.The results showed that the biofilm process lasted for 43 days,the removal rate of COD_Cr,NH₃-N and chroma reached 80.93%,73.81%and 56.79%respectively,blue biofilm attached surface of filling with Vorticella,Arcella,a.hemprichi etc.can be observed.The best operating conditions of the system were determined by single factor experiment,The inlet water temperature and pH range were 21 to 25?and 7.9 to 8.6,the hydraulic retention time was12.25h,the gas water ratio was 10:1.Secondly,the biofilm microbial biomass of different filling height was measured by lipid-P method in optimal operating condition.The changes of biomass in filter and the regularity of pollutant removal along filling were studied.The biofilm structure of bottom and top of filter were characterized by SEM.Then,the kinetic model of organic substrate degradation was established.The results showed that the total amount of phospholipids decreased gradually with the increase of filling.Especially,the total amount of phospholipids decreased significantly at 5to 15 cm of filling.The change laws of biomass per unit mass or volume carrier was the same as that of total phosphorus.The removal of COD_Cr,NH₃-N and chroma mainly concentrated in the height of below 35 cm of filling.The variation as same as the distribution process of biomass along the filter,that the biomass and pollutants degradation rate decreased with the filling.The biofilm of bottom filter was thicker,and the surface was concave and convex,which showed the spatial extension structure formed by filamentous microorganisms.On the contrary,the surface of the biofilm was relatively smooth,and with the large hole and sparse structure at top of filter,which indicated that the interception effect of the filter was mainly concentrated at the inlet end.At last,the kinetic model was determined by analyzing the COD_Crr of different height filling and hydraulic loading.The model parameters n and K₂ of organic compound degradation kinetic were 0.2022 and 0.0406.Finally,the treatment of actual printing and dyeing wastewate was researched by using BAF system.The pollutants degradation in BAF was investigated.The substrate degradation kinetics model of BAF was verified.The influent flow rate of RO and its pretreatment were determined.Then,the treatment efficiency of BAF and RO on the actual printing and dyeing wastewater was evaluated.The results showed that the removal rate of COD_Cr,NH₃-N,chroma and turbidity were 91.82%,79.70%,69.53%and 73.38%,respectively,after continuous operation last 12 days.The measured values of organics with different filling layer height were slightly higher than the simulated values.However,the middle part of the filling layer suited well,which can achieve the purpose of predicting the effluent effect,according to the concentration of influent organics.The influent flow rate and pressure drop of RO were 30 L·h^-11 and 0.14 MPa respectively,and its pretreatment flow rate was 20 L·h^-1.At last,the treatment of actual printing and dyeing wastewate was researched by the integrated technique of BAF and RO.the effluent COD_Crr was lower than 4.08 mg·L^-1,the turbidity was lower than 0.18 NTU,the color was 1 times,the conductivity was less than 10?s·cm^-1,which could achieve the requirements of printing and dyeing wastewater reuse.