Policy Interpretation
"Technical Specifications for Treatment and Disposal of Sludge in Urban Sewage Treatment Plants"
July 27
"Technical Specifications for Treatment and Disposal of Sludge in Urban Sewage Treatment Plants"
Formally implemented
This standard specifies the treatment and disposal measures for sludge in urban sewage treatment plants, and proposes recommended disposal methods according to different regions. It clarifies the pollution control requirements in the sludge disposal process, and provides technical support for the pollution control and resource utilization of sludge in urban sewage treatment plants. Let's take a look at the detailed interpretation.
What is the background and significance of the introduction of the standard?
Sludge in urban sewage treatment plants refers to semi-solid or solid substances with different water contents produced during the purification of urban sewage, excluding screen residues, scum and grit in grit chambers, and is an inevitable product of sewage treatment plants. Sludge contains organic matter, nitrogen, phosphorus, potassium and various trace elements with potential utilization value. In addition, it also contains pathogenic substances such as parasite eggs and pathogenic microorganisms, heavy metals such as copper, lead and chromium, and difficult-to-degrade toxic and harmful substances such as polychlorinated biphenyls and polycyclic aromatic hydrocarbons. If not properly disposed of, it is easy to cause secondary pollution. Because long-term emphasis has been placed on wastewater treatment and less emphasis has been placed on sludge treatment and disposal, sludge disposal technology has lagged behind.
The sludge disposal methods in our province include landfill, land utilization, building material utilization and incineration, but landfill is still the main method at present, and the resource utilization rate is low. Due to the unclear characteristics of mud and the unclear impact on the ecological environment after disposal, the sludge disposal methods of urban sewage treatment plants in our province lack pertinence. Although the country has successively issued a series of policies and standards on sludge treatment and disposal, they have the characteristics of early release, no consideration of regional differences and lack of pertinence. For a certain city or county in our province, the sludge disposal method is still unknown, resulting in the current stage of sludge disposal becoming an important bottleneck restricting the healthy development of urban sewage treatment plants. Solving the sludge disposal problem is imminent.
In response to the lack of sludge treatment and disposal standards suitable for different regions in northern Shaanxi, Guanzhong and southern Shaanxi, the Provincial Department of Ecology and Environment has formulated the "Technical Specifications for Sludge Treatment and Disposal of Urban Wastewater Treatment Plants". The implementation of the standard will improve the standardization level of sludge treatment and disposal in our province in terms of design, operation and maintenance, and management, promote the healthy and benign development of the urban sewage treatment industry, and promote the ecological protection and high-quality development of the Yellow River Basin in our province, as well as the water quality safety of the water source conservation area of the South-to-North Water Diversion Project's Middle Route.
What scope does the standard apply to?
Applicable to the design, construction, operation, management, completion acceptance and environmental impact assessment of sludge treatment and disposal in urban sewage treatment plants.
Not applicable to various types of industrial sludge.
What does the standard stipulate?
First, it standardizes the technical requirements for five types of sludge treatment and four types of disposal in urban sewage treatment plants;
Second, it proposes recommended sludge disposal methods for different regions;
Third, it clarifies the operating environment requirements and pollutant emission standards during sludge treatment and disposal.
What are the recommended sludge disposal methods in different regions of our province?
Guanzhong region: The recommended order of sludge disposal in Xi'an is incineration or building material utilization, land utilization, and landfill. The recommended order of sludge disposal in Baoji City, Tongchuan City, Weinan City, Yangling Agricultural High-tech Industrial Demonstration Zone, and Hancheng City is land utilization or building material utilization, incineration, and landfill. The recommended order of sludge disposal in Xianyang City is incineration or land utilization, building material utilization, and landfill.
Northern Shaanxi: The recommended order of sludge disposal is land use, building material utilization, incineration, and landfill.
Southern Shaanxi: The recommended order of sludge disposal is land use, incineration, building material utilization, and landfill.
What principles should sludge disposal units follow when choosing sludge disposal methods? What matters should be paid attention to?
The selection of sludge disposal methods should follow three principles:
First, the principle of "resource utilization and incineration as the main, landfill as the auxiliary" should be followed, and the sludge output, mud characteristics, geographical location, sludge transportation, environmental conditions and economic and social development level should be comprehensively considered to reasonably select the disposal method.
Second, sludge disposal should comply with the regional sludge treatment and disposal plan, combined with local reality, and coordinated with relevant plans such as environmental sanitation and land use.
Third, according to the sludge disposal method, the corresponding sludge treatment technology should be selected. For example, when the sludge is disposed by land use, it is advisable to select anaerobic digestion, aerobic fermentation and other treatment technologies; when it is disposed by incineration, it is advisable to select thermal drying and other treatment technologies; when it is disposed by building materials utilization, it is advisable to select thermal drying and lime stabilization and other treatment technologies; when it is disposed by landfill, it is advisable to select concentrated dehydration, thermal drying, lime stabilization and other treatment technologies.
Relevant precautions include five aspects:
First, if there are saline-alkali land, desertified land and abandoned mines near the sludge location, it is advisable to adopt land use methods, such as soil remediation and improvement.
Second, if there is a thermal power plant or a waste incineration plant near the sludge site, incineration should be adopted.
Third, if there is a cement plant or a brick factory near the sludge site, building materials should be used.
Fourth, if there is a sanitary landfill near the sludge site, it should be used as a landfill cover soil additive.
Fifth, when the land resources at the sludge site are scarce, incineration or building materials should be used.
What are the specific ways of sludge land use in this standard? What monitoring should be done on the sludge and the application site before and after sludge land use?
The ways of sludge land use in this standard include landscaping, forest land use, soil remediation and improvement.
Before sludge land use, the sludge disposal unit should monitor the pollutants in the sludge. The larger the application amount, the higher the monitoring frequency. At the same time, the background values of various pollutant indicators in the soil and groundwater of the application site should be monitored.
After sludge land use, the sludge disposal unit should regularly monitor the soil and groundwater after the sludge is applied, and observe the growth of plants.
Monitoring and observation records should be kept for more than 5 years.
Is it necessary to pre-treat the sludge before anaerobic digestion?
At present, anaerobic digestion is one of the commonly used methods for sludge treatment in urban sewage treatment plants. The anaerobic digestion process mainly consists of four stages: hydrolysis, acidification, acetic acid production and methane production. Since most of the nutrient matrix required by microorganisms in the hydrolysis process exists inside the sludge flocs and microbial cell membranes (walls), the anaerobic digestion rate is limited when the extracellular enzymes are not in sufficient contact with the nutrient matrix. Effective sludge pretreatment technology can be used to destroy the sludge flocs and sludge cell membranes (walls), release the nutrient matrix, and improve the efficiency of anaerobic digestion.
What factors should be considered when building centralized aerobic fermentation facilities?
During transportation and long-term accumulation, dehydrated sludge may spill sludge, emit odor, etc., which will harm the urban environment and atmospheric environment. Therefore, its site selection should comply with the local urban construction master plan, ecological environment protection plan, urban environmental sanitation professional plan and other relevant regulations, and fully consult the opinions of local people.
At the same time, the treatment and transportation capacity of each link in the sludge operation route should be reasonably configured, and the relationship between the project treatment volume and the acceptable volume should be comprehensively considered to ensure the deep decomposition of the sludge after fermentation and improve the safety of land use.