Full-scale Debugging Research On The Absence Of Pretreating Fine Chemical Wastewater

At present,China is promoting the comprehensive implementation of the“Water Pollution Prevention Action Plan”with environmental protection supervision,which shows that the Chinese government’s supervision of environmental protection is increasing day by day.Fine chemical wastewater is a typical high-salinity,highly toxic,and biodegradable organic wastewater.If it is not effectively treated and discharged,it will bring great resistance to the completion of the“Water Ten”target.Therefore,stable treatment of fine chemical wastewater is particularly important to reach the standard.A company daily treats 2000 m~3 of fine chemical wastewater,among which have a total of 33 different wastewater in 9 workshops.The composition of wastewater is very complex,and it belongs to high salt and refractory organic wastewater.Under the specified of project contract that the effluent from the workshop must be pretreated before entering the sewage treatment station,water quality index of sewage plant design is:COD≤3000 mg/L、ammonia nitrogen≤100 mg/L、total phosphorus acuities≤15mg/L、the total salt≤15000 mg/L、p H=6-9;water quality indicators are:COD≤450 mg/L,ammonia nitrogen≤30mg/L,total phosphorus≤2mg/L,total salt≤15,000mg/L,p H=6-9.According to the pilot-scale test results and referring to previous engineering experience,the treatment process of this project is"coagulation precipitation-hydrolytic acidification-two-stage A/O-flocculation precipitation".In fact,the company each workshop wastewater pretreatment is hardly running,causes the disputes over environmental protection engineering,environmental protection company eventually compromise,adjust the scene debugging focus for when preprocessing the absence of the fine chemical industry wastewater treatment system operation of the study:(1)explore how to quickly and efficiently solve the series of problems caused by absence of pretreatment,study the optimal condition of debugging and running of production,analysis the relationship between the various conditions and the effluent water quality;(2)compare the difference between engineering practice and small test,theoretical analysis of the problems in this project and put forward specific solutions;(3)explore the optimal operation plan that takes into account the treatment effect and capital investment,and make the cost the lowest under the premise of ensuring the effluent standard.The debugging and operation research for more than half a year shows that:(1)the main units of COD degradation in this project are hydrolysis and acidification pool and two-stage A/O pool;Nitrification and denitrification were first used for denitrification,and then point-breaking chlorination was used to strengthen denitrification.Phosphorus removal was carried out by chemical method,that is,adding coagulant aluminum chloride and flocculant polyacrylamide to produce flocculant precipitation,and then phosphorus was removed from the system through mud discharge;(2)glucose was used as the denitrifying carbon source,and the total volume load was up to 0.16kg/m~3.Due to the low concentration of sludge,the actual load did not reach the expected,so the biological nitrogen removal effect is not good enough;(3)the lab-scale test results show that,when the sodium hypochlorite dosage is 3 L/m~3,the effluent ammonia nitrogen can reach the standard stably and the cost is the lowest;(4)the lab-scale test results show that,if the nitrogen removal only use(hypoxia+aerobic)biological method,it is necessary to control the COD volume load in 0.8 kg/m~3·d,at this time the effluent ammonia nitrogen can be stable standard,which speculated that the wastewater contains strong inhibition of microbial activity of the material;(5)the lab-scale test results show that chemical phosphorus removal using polymerized iron sulfate effect is better,and the site selection of lower price of polyaluminium chloride as a coagulant,also can make the effluent TP stable standard;(6)fine chemical wastewater water quality is complex and toxic,direct biological treatment is difficult to normal commissioning and operation,and effective pretreatment is to improve its biodegradability of the necessary means,but also to ensure the stability of water quality standards is an important link.It is suggested that legislation should be passed to increase the investment of environmental protection funds in chemical enterprises.