Study On The Process Of Caprolactam Production Plant Wastewater Treatment

The composition of caprolactam wastewater is very complex, and the fluctuation of water quality and quantity is very volatile. There are many impurities in the waste water,caprolactam, cyclohexanone, cyclohexane, aromatics, methane, tert-butyl alcohol, toluene,ammonia nitrogen, ammonium sulfate and so on. The ratio of BOD and COD is 0,857(caprolactam is very easy to be degraded by microorganism, and produce ammonia nitrogen). The mass concentration ratio of COD and NH3 - N in the wastewater is 14?18,the difficulty and the emphasis of wastewater treatment is ammonia nitrogen(include Organic nitrogen, volatilization of ammonia and ammonium salt), oils(include the emulsified oil, solvent naphtha and other light component, etc) and Organic matter,because, the ring compounds is difficult to be degraded, like benzene, toluene, and anthraquinone.From shijiazhuang chemical fiber and baling petrochemical, in the sewage system of caprolactam, COD generally between 6000-8000 mg/L, and ammonia nitrogen is about 500 mg/L, if only use the traditional A/O sewage treatment and SBR process is very difficult to reach the national standards. Shijiazhuang chemical fiber use biological multiplication method, this is a advanced method of wastewater treatment, but the high cost of aeration, dissolved oxygen control is not very stable. The baling petrochemical use hydrolyzing A / O+MBR, MBR is a effective combination of membrane separation technology and biological treatment, but the process has high energy consumption, and the membrane is easy to appear problem, running cost is also high. In order to make the issue of water reach the national standard level, in the case of consumption is reasonable,choosing a appropriate process become a technical problem in the project.This paper provides the research topic of oil separating and gas floating pretreatment+ hydrolytic acidification + A/O system of biochemical treatment process + coagulation sedimentation depth treatment technology to deal with caprolactam sewage. And the traditional craft to take the following adjustments: accident pool diving blender to UPVC perforation of the trachea, timely on accident sewage aeration, reducing waste water pollutant concentration; Aerobic pool dosing activated carbon changed to coagulation precipitation in adding the activated carbon to reduce bleaching clay; For hydrogen peroxide, cyclohexanone, caprolactam plant wastewater characteristics, the corresponding pretreatment water drainage for each device, not only increase the material recycling, but also reduce the concentration of the pollutants in the waste water, to alleviate the integrated processing load. In the pretreatment stage, in view of the oil and suspended solids, using oil separating and gas floating technology, to remove the oil and suspended solids in the wastewater. In view of the high concentration of ammonia nitrogen, in the form of biological denitrification, the use of denitrifying bacteria for degradation of ammonia nitrogen, by controlling suitable reflux ratio and nitrification of ammonia nitrogen, nitrifying liquid back into anoxic stage at the same time, the use of wastewater in relatively high concentrations of BOD as carbon source, providing the power for the denitrification process. In view of the high concentration of organic matter, the combination of anaerobic + aerobic process both economic and reasonable, high efficiency and can remove most of the COD. UBF technology, using anaerobic microorganisms efficient degradation of organic pollutants in wastewater, and will release a large amount of organic nitrogen in the form of ammonia nitrogen, nitrification and denitrification for subsequent provide strong conditions. Caprolactam waste water discharged into waste water station, pump up to the separation tank, remove most of the heavy oil, light oil, etc. using gravity oil collection to oil pool. Oil separation tank artesian water into the regulation pool, adjust the pool with diving blender mixed stirring,balanced water. Adjusting the pool water pump up to the gas floating pool, in the role of demulsifier and coagulant , removing surplus oil and suspended solids, etc.In the main biochemical stage, in the role of hydrolysis acidification bacteria, part of the macromolecular substances will be degraded, to offer good substrates for subsequent anaerobic treatment. Hydrolysis of pool water up to the UBF by acidification of the wastewater in the role of methanogens, removing most of the organic matter, reducing the load of the follow-up biochemical and ammonia nitrogen. Organic nitrogen in the wastewater can be converted to follow-up denitrification process. UBF pool water from flowing into the A/O system, using the BOD in the wastewater material as carbon source denitrification; Making use of mixed aeration process, adopt of microbial metabolism,maximum cutting waste water COD and ammonia nitrogen, etc. O pool nitrifying liquid back into A pool. O pool water from flowing into two spate separation pond, the second pond sludge circumfluence to the A/O section, ensure activated sludge concentration in the pool. The second pond effluent can reach the requirements of the second phase water quality treatment. In order to reach the level of national requirements, it is necessary to add a physico-chemical depth treatment technology after the biochemical process. Main biochemical effluent into the coagulation sedimentation tank, in under the action of PAC and PAM to remove suspended solids and colloidal impurities,etc. through coagulation precipitation, let water reach the national standard.