Treatment method of landfill leachate reverse osmosis concentrate

Abstract

The invention relates to a garbage leachate reverse-osmosis concentrate treatment method, which comprises the following steps: pouring acid into a reverse-osmosis concentrate to reduce alkalinity of the concentrate, introducing the feed liquid into a degassing membrane tube, removing carbon dioxide gas and discharging the degassed concentrate into a sealed neutralization tank, pouring alkali into the neutralization tank, adjusting pH of the feed liquid to 6.5-7.5, preheating and letting the feed liquid enter a first-stage mechanical compression evaporator to carry out forced-circulation heat-exchange evaporation, carrying out forced-circulation heat-exchange evaporation by a second-stage mechanical compression evaporator, controlling liquid-solid rate to 28-35%, carrying out quality-based crystallization to obtain sodium salt and sylvite, processing high-concentration mother liquor and recovering humus, and pumping a separating medium or a supernatant inside a coagulative precipitation tank back into the second-stage mechanical compression evaporator and continuously evaporating. Operation load of each stage can be effectively reduced, the influence of humus accumulation in the concentrate and other unfavorable factors is reduced, continuous and stable operation of the evaporation system can be guaranteed, and zero emission of the reverse-osmosis concentrate can be realized.

Description

technical field [0001] The invention relates to a method for treating landfill leachate reverse osmosis concentrated liquid, belonging to the technical field of high-salt wastewater treatment. Background technique [0002] For landfill leachate treatment, the combined process of "pretreatment + biological treatment + advanced treatment" is widely used at present. Advanced treatment includes nanofiltration and reverse osmosis treatment processes, but the concentrated liquid produced by the membrane unit is relatively large, accounting for about 20% of the volume of landfill leachate, so it is necessary to properly dispose of the concentrated liquid from membrane filtration. [0003] The reverse osmosis concentrate is enriched with most of the salt in the leachate, and organic substances that are difficult to biodegrade or cannot be biodegraded. If the recharge method is used for a long time, it will lead to the continuous accumulation of salt and other pollutants in the land...

AI Technical Summary

Problems solved by technology

However, there are many disadvantages in this method: (1), the amount of dosing is very large, the pH of the raw water needs to be adjusted to more than 10 by adding alkali, and the pH of the effluent needs to be adjusted to neutral by adding acid after precipitation

(2) A lot of chemical sludge is produced, the sludge settleability is very poor, the separation effect is poor, and the effluent contains flocs, which need to be further filtered

(3) Chemical sludge is treated as hazardous waste, and the treatment cost is relatively high

(4) Large-volume structures such as dosing tanks, reaction tanks, and sedimentation tanks are required, and the investment and operating costs are relatively high

[0005] In addition, the evaporation treatment of the concentrated liquid usually adopts one-stage evaporation, and the accumulation of humus and other harmful factors in the concentrated liquid are difficult to control, so the single-stage mechanical compression evaporation method has a large processing load and high energy consumption

In particular, the concentrate in the evaporator always maintains a state of high solid content, which is not conducive to the operation of the equipment. If any equipment is damaged, it can only be shut down for maintenance, and the requirements for operation and management are very high.

However, the reverse osmosis concentrate of landfill leachate contains a large amount of macromolecular humus that is difficult to biodegrade, which is continuously concentrated during the evaporation process, resulting in an increase in the viscosity of the feed liquid, which affects the crystallization of salt, and is not conducive to the stable operation of the evaporation process.

Patent application CN104496103A and patent CN103626314A use a material separation membrane to isolate humus, but the separation membrane has poor tolerance to organic pollutants, the actual water production rate is very low, and the humus cannot be completely filtered, and the trace amount of humus in the clear liquid will also be in the Continuous concentration in the evaporation system cannot completely solve the problem of continuous and stable operation of the evaporation system

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