What are the influencing factors of landfill leachate treatment by evaporation?

　　Among all kinds of advanced treatment technologies of landfill leachate, nanofiltration and reverse osmosis are widely used. While nanofiltration and reverse osmosis equipment discharge supernatant, membrane separation process will produce certain concentrated solution.
　　The membrane concentrated solution of landfill leachate has the characteristics of complex composition, high organic concentration, poor biodegradability and high salt content, which is difficult to treat.
　　1. Treatment of membrane concentrated solution of landfill leachate by evaporation method
　　Evaporation treatment technology uses heating to evaporate the water in the membrane concentrated solution, so that the volume of the membrane concentrated solution is obviously reduced. In the actual evaporation process, only a small part of volatile organic acids, ammonia and volatile substances will enter the condensate with steam, while all inorganic substances, heavy metals and most organic substances will remain in the remaining concentrated solution.
　　The evaporation treatment process can concentrate the leachate to about 2% ~10% of the original volume. Evaporation treatment of membrane concentrated solution has the characteristics of strong adaptability to the change of water quality and quantity, less concentrated solution, and the operating cost of evaporation treatment of concentrated solution can be reduced by low-energy energy recycling technology, so it is feasible and economical to treat membrane concentrated solution of landfill leachate by low-energy evaporation.
　　2. What are the influencing factors of landfill leachate treatment by evaporation?
　　1. The initial pH of membrane concentrated solution has great influence on COD and NH3N-N in the condensate. Under acidic conditions, the concentration of COD in condensate is very high, but the content of NH3N is very low. Under alkaline conditions, the concentration of COD in condensate is very low, but the content of NH3N is high. Because the reverse osmosis effluent is acidic, it is economical and effective for evaporation system to treat the membrane concentrated solution of reverse osmosis system under acidic conditions.
　　2. Evaporation temperature has a certain influence on the water quality of condensate: with the increase of evaporation temperature, the pH, TDS and NH _ 3N of condensate increase, reach a maximum at 70℃, and then decrease; UVy increases with the increase of temperature; The COD in condensate decreases with the increase of temperature, and the COD in the corresponding residual liquid increases with the increase of temperature.
　　3. The evaporation rate has a certain influence on the water quality of condensate: with the increase of evaporation rate, the TDS of condensate decreases, reaching the lowest value when the evaporation rate is 72%, and then increases with the increase of evaporation rate, but the increase rate is small, and the decrease rate of TDS is more obvious in the initial stage of evaporation than in the middle stage of evaporation; At the initial stage of evaporation, the content of NH3-N in the condensate was high, and the pH was high. With the increase of evaporation rate, the content of NH3-N in the condensate decreased, and the pH decreased. At the later stage of evaporation, the content of NH3-N in the condensate increased slowly, but with little amplitude.
　　4. The concentration of TDS in condensate is closely related to the concentration of NH3-N: TDS in condensate mainly comes from NH3-N evaporated into condensate.