Sludge treatment scheme

With the economic development and the strengthening of environmental protection awareness, the sewage treatment industry in small towns has been developing continuously. The total amount and degree of treatment of sewage plants will continue to expand and improve, and the amount of sludge generated will also increase. The investment and operation cost of sludge treatment and disposal are relatively high. If the sludge is improperly disposed, it will cause "secondary pollution", which has become a problem in the field of environmental protection and has attracted much attention.

Current Situation and Development Trend of Sludge Treatment and Disposal at Home and Abroad

Current situation of sludge treatment and disposal at home and abroad

At present, mature sludge stabilization processes commonly used at home and abroad include anaerobic digestion, aerobic digestion, heat treatment, heating drying and alkali addition stabilization; The commonly used sludge disposal is land use, incineration, sanitary landfill, composting, sea investment, building materials, etc.

Due to technical and economic constraints, the current sludge disposal in China is still dominated by landfill, supplemented by sludge utilization. Sludge investment in the sea accounts for a certain proportion in coastal cities, but the total amount is small. Sludge incineration has not started yet. In terms of sludge utilization, sludge is used more for agriculture, forestry and greening after natural drying. Sewage plants using mechanical dryers to dry sludge include Dalian Development Zone Sewage Plant, Qinhuangdao Sewage Treatment Plant and Xuzhou Sewage Treatment Plant. However, these plants have small capacity (3~12t/d dry sludge) and heavy odor pollution. Although the investment is low, the effect is not ideal. At present, foreign sewage plant sludge mainly adopts agricultural utilization, landfill, and some other treatment methods such as incineration. According to the statistical data of Japan in 1994, the annual output of urban sludge in Japan is 2.307 million tons, and its disposal methods are: land and coastal landfills account for 62.7%; Resources utilization accounted for 24.9%, and other disposal accounted for 12.4%. In recent years, 80% of sludge has been landfilled in Germany, 8% for agriculture and 4% for compost; According to the statistics of the US Environmental Protection Agency, in recent years, 35% of sludge has been landfilled, 15% has been incinerated, 49% has been used for agricultural or other land, and 1% has been disposed of.

It can be seen that agriculture and landfilling are currently the main methods for sludge disposal in most countries. The choice of agriculture and landfilling schemes largely depends on the relevant laws, regulations and pollution source control of governments, as well as national agricultural development. In recent years, the proportion of sludge for agricultural use in the United States, Japan and the United Kingdom has increased; However, in some countries, such as Germany and Denmark, due to the increasingly strict agricultural standards for sludge, the proportion of sludge for agricultural use has been declining, and the proportion of other treatment methods, such as incineration, has increased.

Development of Sludge Treatment and Disposal Technology

Sludge stabilization treatment

The purpose of sludge stabilization is to turn the sludge into a stable (i.e. non perishable) product through treatment, so as to further dispose and utilize it. The sludge stabilization process can also kill some pathogens and reduce the odor in the sludge. Anaerobic digestion and composting are commonly used stabilization processes in China. There are four commonly used stabilization processes in the United States: anaerobic digestion, aerobic digestion, composting and alkali stabilization.