Explanation of zero-discharge technology for coal chemical industry wastewater

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It provides a detailed introduction to the methods used for controlling organic substances, as well as ammonia and nitrate nitrogen, in current wastewater treatment processes. It explores the concentration ratio in brine membrane concentration and the design for resin-based hardness removal, compares the roles of evaporators and membrane concentration in brine concentration, and discusses in detail the process options for the recycling of crystallized salts. 1. The impact of organic substances on zero-emission systems: (1) Organic substances can cause contamination or biofouling of reverse osmosis and nanofiltration membranes, leading to frequent cleaning of these membranes, a reduction in their operational efficiency, and a shortened membrane lifespan ； (2) A high concentration of organic substances can easily cause the evaporation crystallization unit to produce excessive foam, leading to the formation of flying material; however, the concentration of organic substances is not necessarily the main factor causing such flying material ； (3) High concentrations of organic matter in the crystallizer affect the quality of the crystalline salt. 2. Control of organic matter: Common methods for controlling organic matter include: (1) Enhancing the efficiency of biochemical treatment, which is the most cost-effective approach; this can be achieved by adding fillers or special microorganisms to the biochemical reaction tanks ； (2) Select a advanced treatment process suitable for the characteristics of the water quality, such as advanced oxidation, Fenton process, adsorption, etc ； (3) Adding non-oxidizing biocides to the ultrafiltration-reverse osmosis membrane system and raising the pH value of the system’s operation, in order to reduce the contamination of the membrane system by organic substances and microorganisms ； (4) Add an antifoaming agent to the evaporation crystallization unit to stabilize operating parameters and prevent material from escaping ； (5) A washing device is installed at the salt outlet of the crystallizer to reduce the amount of organic matter carried by the crystallized salt. The following introduces several typical treatment processes: 2.1 Powdered activated carbon – MBR bioreactor (PMBR). This system utilizes an aerobic tank with PMBR; powdered activated carbon is combined with activated sludge, taking advantage of both the adsorption capabilities of activated carbon and those of the biological filler. Large, hard-to-degrade organic molecules are effectively adsorbed, thereby increasing the retention time of pollutants (PRT). The surface of the filler provides better conditions for biological growth, thus enhancing the efficiency of the aerobic tank in wastewater treatment. Pilot test results using this technology on the biochemical influent at the Yima Gasification Plant showed that the COD level in the effluent from the aeration tank could be reduced to 80 mg/L ； After 6 months of pilot-scale operation using the AO(PMBR)+RO process for treating phenol-containing wastewater in Datang Keqi, the COD level in the water exiting the PMBR remained below 100 mg/L, TN was stable at 10–20 mg/L, and NH4-N was around 1–2 mg/L. The SDI of the water exiting the PMBR