| The treatment of this project is cleaning a pesticide enterprise’s waste water which is poor biochemical purification,toxic and harmful,difficult to storage and transporte.Coagulation membrane thickening process was conducted according to it’s characters,which combined with membrane concentration and coagulation pretreatment.The feasibility of the coagulation membrane process in directly concentrating waste water was studied and applied into engineering practice.First,according to the untreated water quality,select the poly aluminum chloride as coagulant,waste liquid p H,PAM,PAC put amount as single factor for the beaker test in order to select the best coagulation conditions according to the untreated water quality.The results showed that the optimum coagulation conditions of No.1 waste liquid were as follows: PAC is 3g / L,PAM is2 mg / L,pH is 9;the optimum coagulation conditions of No.2 waste liquid were as follows:PAC is 1.5g / L,PAM is 1mg / L,the pH value is 8;the best coagulation conditions of No.3 waste liquid were: PAC is 0.3g / L,PAM is 0.8mg / L,waste liquid pH value is 8.Conclusion: The best coagulation conditions are different for different waste water.This experiment laid the foundation for the next film treatment.the concentration of the actual waste liquid and water quality should be put in accordance with the appropriate proportion.Secondly,the pilot scale test was performed to serially determinate,analyze,treat and record membrane flux data,investigating the effects of the process and the change of membrane flux and validating the feasibility of enriching the pesticide hazardous waste according to waster water’s turbidity,chemical oxygen demand,total organic carbon,conductivity,and active ingredients.The results showed that:(1)coagulation has a better removal effect on the turbidityand the removal rate is 95%.Coagulation can meet the requirements of ultrafiltration membrane.(2)the process has a better and stable remove the effect to organic matter.The removal rate of COD,TOC reached 98.5%,98.6%,respectively,and the CODof reverse osmosis effluent is about 179 mg / L,TOC is about 50 mg / L,which meet the enterprise‘s internal control standard.(3)reverse osmosis membrane has a better retention of ions which has a better effect on remocing the conductivity.Reverse osmosis effluent’s conductivity is within 100μS / cm and the water quality is better.(4)The process has a better removal effect on the active ingredients of the drug and the removal rate reached 99.9%,which meet the company’s internal emission requirements.(5)After cleaning,the recovery rates of the ultrafiltration membrane,RO membrane and nanofiltration membrane flux were 96.8%,89.3% and 99.8% respectively.The cleaning method and cleaning frequency of the membrane were basically determined after one month stable operation,which provided the law of film cleaning in the actual project.Conclusion: The process has good effect on the removal of pollutants.and the membrane flux is stable during the operation.Besides,it is feasible to concentrate pesticide hazardous waste by the multi-stage membrane.During the pilot scale test,the effects of hydrochloric acid,citric acid,sodium hydroxide and sodium dodecyl benzene sulfonate on cleaning the reverse osmosis membrane were compared.The reason of the reverse osmosis membrane and the membrane cleaning program were investigated to give a rapid and efficient cleaning way to restore the flux of reverse osmosis membrane.The results showed that:(1)The main cause of membrane fouling is organic pollution and microbial contamination when the hazardous waste liquid is concentrated by reverse osmosis membrane.(2)citric acid,hydrochloric acid,sodium hydroxide,sodium dodecyl benzene sulfonate all have a certain effect on restoring the membrane flux while it can not return the membrane flux back to the initial level.The comparision among single cleaning effect is as follows: sodium hydroxide>sodium dodecyl benzene sulfonate >hydrochloric acid >citric acid and it’s recoveries of membrane flux were 70.8%,69.6%,48.5% and 41.4%,respectively.(3)The combined cleaning effect is better than the single cleaning effect.Among them,the cleaning effect of sodium hydroxide wash-dodecyl benzene combined with sulfonate wash-citric acid pickling cleaning method is the best,and the membrane flux recovery rate is 85.9%.(4)the amount of cleaning solution,cleaning pressure,cleaning time have a certain impact on the membrane flux recovery rate.This study determine the best cleaning conditions namely,0.1% sodium hydroxide + 0.025% dodecyl benzene Sodium sulfonate + 3% citric acid with cleaning pressure is 0.4MPa,cleaning time is 30 minutes,cleaning temperature is 25 ℃.Conclusion: Organic pollution is the main cause of membrane fouling through the analysis of cleaning effect.There has 3 steps to determine the reverse osmosis membrane cleaning,first of all,0.1% sodium hydroxide wash,secondly,0.025% sodium dodecyl benzene sulfonate,thirdly,3% citric acid was added to wash.Finally,the coagulation-membrane concentration treatment process is applied to engineering practice which it’s designed capacity is 5t / d for 8 hours.The results showed that:(1)the system is stable and reliable with efficient treatment,water quality of the effluent can meet the enterprise‘s internal control standard.(2)system design waterproducting rate is 70% and the water production rate is more than 70% during the operation of the system,which meets the design requirements.(3)The process sets the ultrafiltration membrane flux as 8 L/h/m2,RO membrane flux as 9 L/h/m2,nanofiltration flux as 20 L/h/m2.The membrane flux is stable during system operation.(4)The process will reduce the annual waste processing costs of 500,000 enterprises,showing significant economic benefits.Conclusion: the system is stable and reliable with efficient treatment,water quality of the effluent can meet the enterprise‘s internal control standard,and the economic and social benefits are remarkable.In summary,the application of multi-stage film condensed pesticide hazardous waste is technically feasiblehas which has a cost-effective wastewater treatment equipment with good economic benefits and broad application prospects. |
PDF Full Text Request