The main pollutants in hydroxypropyl methylcellulose wastewater are sodium chloride, isopropanol, hemicellulose derivatives, loss of cellulose ether products, etc. The content of CODcr (dichromate oxygen demand) in the wastewater can reache 60,000 mg/l and the salt content can reach 80,000 mg/l.The mass concentration is as high as 7% to 8%. It belongs to high-concentration salt-containing and refractory wastewater.

The high osmotic pressure of hydroxypropyl methylcellulose wastewater and its high concentration of salt ions are inherently toxic to microorganisms.If we use conventional treatment processes such as "anaerobic + aerobic" process to treat the wastewater, the activity of the microbial in the anaerobic sludge or aerobic sludge will reduce and even lose activity or die. In order to maintain the operation of the system, sludge must be continuously added to keep the sludge volume of the system. The traditional treatment process is poor in sewage treatment efficiency, and unstable in operation. The water treated is difficult to meet the discharge standard and reuse water quality.

Considering the difficulty of cellulose wastewater treatment and the actual situation, we adopt combined treatment process: evaporation + micro-electrolysis + Fenton oxidation + UASB + hydrolysis acidification + contact oxidation + advanced oxidation.and the wastewater produced by hydroxypropyl methylcellulose is collected. The wastewater is collected and deliveryed to the adjusting pool and then lifted into the evaporator by the pump.

The concentrated liquid evaporated by the evaporator is centrifuged and separated by centrifugation, and the salt will come out for reuse or other disposal.The rest concentrated liquid will be mixed with other process wastewater to adjust,.Then the micro-electrolysis and Fenton oxidationfen will conduct.This is mainly to oxidize some of the macromolecular organics into small molecules, which facilitates the subsequent biochemical treatment.The mixed wastewater after oxidation will be pumped into the UASB.The anaerobic reaction process in the UASB reactor is the same as other anaerobic biological treatment processes, including Hydrolysis, acidification, acetogenic and methanogenic, etc., With the transformation of different microorganisms,the substrate will be converted into the final product - biogas, water and other inorganic substances.

The water from the high-efficiency anaerobic reactor will enter the first sump and the anaerobic sedimentation tank, and the sludge will partially returned to the first sump after being precipitated.The water from the first sump is returned to the UASB through a reflux pump disposed at the bottom of the first sump. The remaining sludge in the anaerobic sedimentation tank is discharged to the sludge concentration tank.Processed by the diaphragm plate frame press filter,the sludgewiil be deliveryed to the dry mud transport system. Since the effluent organic matter of the UASB is mainly a macromolecular organic matter which is difficult to be biochemical directly, it is necessary to convert the macromolecular organic matter into a small size. The UASB effluent enters the second pool, and then enters the hydrolysis acidification tank through the lift pump at the bottom of the pool. The hydrolysis acidification tank decomposes some of the refractory organic matter into small molecular organic substances, which reduces the difficulty of contact oxidation. Air will be blowed into the tank and most of the organic pollutants in the water are catabolized into CO2 and H2O through the metabolism of aerobic microorganisms, and the water quality is further purified. The remaining sludge in the contact oxidation pond is also transported to the sludge concentration tank and treated in the same manner as the remaining sludge in the UASB sedimentation tank. The effluent from the contact oxidation pond enters the reservoir.Part of the dilution water is returned to the integrated wastewater regulation tank and the rest is pumped into the sand filter tank for filtration.Then the filtered water enters the advanced oxidation tank. The substance is oxidized and decomposed by strong oxidant ozone, and the CODcr in the water is further reduced. The effluent of the advanced oxidation tank reaches the discharge water quality standard and is discharged to the wastewater discharge system.

Table 4-1 Removal Efficiency Table