Research Of Starch Wastewater Treatment Process And Engineering Application

Starch and its products are widely used in food,chemical industry and other fields.Starch industry has became one of the most dynamic sectors of national economy.According to the current technical level,the production of 1 ton of starch produced nearly 5 tons of waste water,due to the use of raw materials and production methods,the pollutant content of starch waste water is different,mainly contains starch,protein,nitrogen,phosphorus and other substances.Drainage can worsen water and cause environmental pollution.This study took a company in Xiangtan,Hunan Province as the research object,analyzed the problems of this enterprise's wastewater,consulted the commonly treatment methods used in engineering,and put forward the appropriate treatment process in combination with the conditions of the enterprise.Then,the feasibility of the process and the optimal operation parameters are determined by the pilot study.the optimal operation parameters have provided reference for the engineering.The efficiency and economic cost of the process in practical engineering are studied.The main research and conclusions are as follows:(1)In the laboratory,the coagulation effects of poly aluminum chloride,ferric chloride and aluminum sulfate with different dosage on the starch waste water were studied.The results showed that:the treatment efficiency of ferric chloride was the worst,and the best was poly aluminum chloride,the optimal dosage was 1.25 g/L.Then,The effects of poly acrylamide dosage,pH of waste water and reaction settling time on the coagulation were studied by controlling the dosage of poly aluminum chloride.The optimal reaction condition for coagulation of starch waste water under single-factor experiments was obtained.The orthogonal experiment was designed to optimize the parameters,and the optimal experimental condition was finally determined as follows:the dosage of coagulant was 1.25g/L,the dosage of coagulant was 20 mg/L,the initial reaction pH was 7.5,and the coagulation settling time was 25min.At this time,COD_Crremoval rate is about 60%and SS removal rate is 90%,which can accord the water inlet condition of the subsequent anaerobic reactor and ensure the long-term operation of the anaerobic reactor.(2)An experiment was carried out in a UASB reactor to treat starch wastewater.Controlling the start temperature of reactor at 35?.In the early stage,low concentration wastewater was used to make the sludge adapt to wastewater.and then the concentration was gradually increased to form anaerobic granular sludge and domesticate,the pH,VFA and effluent SS of the UASB are regular;When the volume load increased to 4.5kg COD_Cr/(m³·d),the COD_Crremoval rate drops below 65%,and the reactor acidified.It is recommended that the volume load should not exceed 4 kg COD/(m³·d)when UASB is used to treat such starch wastewater.After the UASB operating stably,the treatment effect of the reactor at different temperatures was studied.When the temperature was 35?,the removal rate of COD_Crmore than 80%,and the treatment effect decreased when the temperature continued to rising.(3)The Biological Contact Oxidation Reactor was started by artificial inoculation with a membrane hanging method.At the early stage of membrane forming,manually configured glucose solution and other required trace elements were added,C:N:P=100:5:1,After 15 days,a biological membrane formed preliminary.At this time,the effluent of the anaerobic reactor was used to acclimate the sludge,and the effluent COD_Crwas continuously increased to 1000 mg/L.After 30 days,the biological membrane was mature,and it noted that the reactor started successfully.After a stable operation of the reactor,the treatment effects of different hydraulic residence time and dissolved oxygen were studied.The results showed that:the COD_Crof the effluent was about 1000 mg/L,the average of ammonia nitrogen was 80 mg/L,total phosphorus concentration was 8mg/L,pH was 7-8,dissolved oxygen was 4-5 mg/L,and the hydraulic residence time was 14 h.The COD_Crremoval rate was 85%,effluent concentration was 143.8 mg/L.The removal rate of ammonia nitrogen was up to 89%,effluent concentration was 8.14 mg/L,total phosphorus removal rate was 77%,effluent concentration was 1.8 mg/L.(4)Coagulation was used as the effluent phosphorus removal process again.The dosage of PAC is 0.4 g/L,PAM's dosage is 4 mg/L,pH between 7-8,the effluent reached standard stably.(5)The process has applied to engineering application.The results show that it is feasible using this process to treat the wastewater,and the final effluent's quality has reached the national first level of the Integrated Wastewater Discharge Standard.After debugging,the removal rates of COD_Cr,ammonia nitrogen and total phosphorus in the whole process reached 99.5%,96.1%and 99.3%respectively.The cost of wastewater treatment is 4.52yuan/m³.For high-concentration and organic wastewater,this process is more economical and has the higher value of reference.