The Study On Pretreatment Of Acrylic Fiber Wastewater

Acrylic fiber wastewater contains masses of toxic and harmful substances which aredifficult to biological degradate. Direct emissions or treatment before being not standarddischarged would cause severe pollution to the water itself. The biochemical treatment systemis the main unit of sewage treatment, while the wastewater contains large quantity of toxic andharmful substances which can cause toxicity on microbial in it. What s more, it can also reducethe efficiency of the biological treatment system. Therefore, we need to find an economic andfeasible pretreatment process to reduce the toxicity of raw water, and we think the key is toimprove the biodegradability of acrylic fiber wastewater s proper discharge.This paper that is based on the analysis of common industrial wastewater pretreatmentprocess mainly studies: the removal effect of pretreatment process such as coagulation andsedimentation method, sand filtration, iron carbon micro electrolysis, Fenton oxidation processto the acrylic fiber wastewater COD, as well as biodegradability enhancement. And it analysesthe feasibilities of all kinds of pretreatment processes from the treatment effect, operation costand operation course etc. The research draws the following conclusion:（1） Comparing FS, PFS, CPFS which is produced in Longzhou EnvironmentalProtection Technology Company in Tangshan in China, with the oxidation of coagulantwhich is produced in a company in Beijing by doing a lot of experiments, we found that theCPFS removal effect on the acrylic fiber wastewater is the best among these four differentcoagulants. Under the pH of raw water being not adjustable case, treatment efficiency wasappeared the best when coagulation was put in800mg/L and coagulant aids were put in8mg/L. And the removal rate of COD reached11.67%. Meanwhile, the biodegradability ofthe wastewater was improved to0.42.（2） Through the continuous sand filter in pilot scale trial operation, with the SS in rawwater acting as560mg/L, and the COD as981mg/L both on average, yielding water and CODreached297mg/L and785mg/L, and it’s average removal rate reached35%and15%. Whilewater seepage reaching to1300mg/L per hour, the removal rate of SS could surprisinglyreached78%. Meanwhile, after continuous sand filter treatment, the raw water could bedegraded to total organic carbon, total carbon, total nitrogen, ammonia nitrogen at varyingdegrees. The biodegradability of the wastewater also increased from the original0.21to about0.33. Continuous sand filter takes on the feather of automatic backwashing, and consumingless power, it also has a strong capacity of resisting impact load.（3） Through the experiments we could see the different effects on iron carbonmicro-electrolysis method because of iron-carbon ratio, Iron dosage, pH value and reaction time to acrylic fiber wastewater treatment, and we confirmed the optimum operationconditions. The results showed that when volume ratio of iron to carbon was1:4, Iron dosingvolume was10ml, pH=5.0, and the reaction time was120min, the removal rate of CODreached33%. The biodegradability of the wastewater could be increased to about0.35.（4） The experiment of Fenton oxidize method resulted when the dosage of hydrogenperoxide was20ml, the dosage of FeSO₄·7H₂O （g） was8g, pH6, and the reaction time was30min, the highest removal rate of COD reached54%. The biodegradability of thewastewater could be increased to about0.33.（5） Through the comparison of the four methods, all of them can remove acrylic fiberwastewater at a certain degree, and they can also improve the biodegradability of thewastewater in different degrees. However, when overall considering from treatmentefficiency, cost of investments, and running expense, coagulation and sedimentation methodis a quite economic and effective pretreatment process.（6） According to the above researches and concerned to a certain amount of whitepowder low polymer contained in acrylic fiber wastewater, which is difficult to precipitate,we used the pretreatment method with coagulation-air flotation and sand filter for the actualengineering pretreatment of acrylic fiber wastewater in Qifeng chemical fibre factory. Thepractical running results showed that when the coagulation-air flotation process with COD inwater seepage acting as656mg/L per hour, the removal rate to COD could reach11%.whencontinuous sand filter s SS and COD40mg/L,660mg/L per hour, it’s removal rate couldreach46%and4%. As a result, coagulation-air flotation and continuous sand filtrationprocess is an ideal pretreatment to acrylic fiber wastewater. The study provides usefulreference for the treatment to acrylic fiber wastewater.