The current main process of waste sludge treatment and disposal:
First, sludge anaerobic fermentation
Anaerobic three stages: hydrolysis, fermentation, methane production.
1, large investment, high operating costs, safety issues.
2, sludge need to preheat and consume a lot of heat.
3, produce a large amount of biogas residue, need to deal with again.
4, methane gas is difficult to incorporate into the municipal pipe network.
5, the northern winter can not run.
Second, sludge aerobic composting
Using straw and other excipients to reduce the water content of sludge to 60%, increase the gap to achieve the required CN ratio, continue to add oxygen, by 25-30 days of fermentation humus. To stabilize,and then can be used as landscaping and land improvement disposal.
Mainly include: natural compost, closed compost, roller compost, vertical multi-layer composting.
1, sludge muddy instability, heavy metal is difficult to stabilize, can only be used as landscaping fertilizer.
2, the composting process produces a lot of odor, which may pollute the surrounding environment.
3, adding a large amount of straw and other conditioning agents, continuous oxygen supply, operating costs 200 yuan / t or more.
Third, sludge incineration power generation
Core equipment is incinerator, the main equipment is the tower, the bottom of the perforated plate, the plate placed on the hot carrier sand burning bed, tower lined with refractory material, the gas from the bottom access, after the sludge into the boiling fluidized state of combustion .
1, large investment, serious corrosion of the boiler, high maintenance costs.
2, high operating costs.
3, a greater impact on exhaust emissions, easy to produce dioxin and other harmful gases.
Fourth, sludge sanitary landfill
Landfill is mainly mixed with rubbish and the landfill site is constructed with the cost of 50-60 yuan / t. It is easy to pollute the water source, the atmosphere and occupy a large area. At present, the land resources used for landfill in our country are tense, Mud landfill will soon be no way out.
Fifth, rotary kiln drying
Using coal or natural gas and other energy to dry sludge dehydration.
1, energy consumption, high operating costs.
2, high temperature drying easy to produce odor.
3, the drying process of dust control requirements, there are security risks.
Six, box filter secondary pressure
The sludge diluted about 90%, after adding pharmaceuticals, secondary pressure filtration.
1, moisture content can only be 75-65%.
2, adding a large number of agents to increase the dry weight of sludge, operating costs higher.
3, the limitations of sludge reuse increased.
Seven, curing agent stability
In the original sludge by adding lime and other curing agent, chemical reaction with the sludge release a lot of heat, reducing water content.
1, add a lot of lime, aluminum-based materials, sludge increment.
2, sludge can not be used again.
3, higher operating costs.
So if relying on a single process, it would be difficult to meet the sludge treatment and disposal requirements. For different regions and different types of sludge, taking into account the climate, regional characteristics, the conditions of the construction site, the combination of a variety of techniques in order to achieve the best results. (Editor:Kosun Lily.Wang)
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Contact person: Lily Wang