Firstly, the sludge generated by public sewage treatment plants, which are used solely for treating domestic sewage in towns and cities, does not normally have hazardous characteristics and can be managed as general solid waste.
In addition, sludge generated by treatment facilities specialised in treating industrial wastewater (or treating a small amount of domestic wastewater at the same time) may have hazardous characteristics and should be identified in accordance with the National List of Hazardous Wastes, the National Environmental Protection Standard Technical Specification for the Identification of Hazardous Wastes (HJ/T298-2007), and the hazardous waste identification standard.
(c) In the third category, if a public sewage treatment plant, whose main function is to treat domestic sewage, receives and treats industrial wastewater, and if that industrial wastewater can stably meet the national or local pollutant discharge standards before it is discharged into the public sewage treatment system, the sludge from the public sewage treatment plant may be managed in accordance with the provisions of the first article. However, in the event of a significant change in the discharge of industrial wastewater, the hazardous characteristics shall be identified in accordance with the provisions of article II.
In the fourth category of cases, where an enterprise discharges industrial wastewater outside its legal boundaries in a direct or indirect manner, the quality of the effluent water shall comply with the national or local pollutant discharge standards; sludge generated in the process of wastewater treatment, which is a solid waste being generated, and for which the hazardous characteristics are to be identified, shall be sampled in the process of wastewater treatment in accordance with the provisions of the "Technical Specification for Identification of Hazardous Wastes" and the minimum number of samples shall be determined in accordance with the amount of sludge generated. The minimum number of samples should be determined according to the amount of sludge generated.

A few typical sludge discriminations

1. Electroplating wastewater and electroplating sludge with excessive heavy metals:
Electroplating sludge belongs to hazardous waste, the waste category often belongs to HW17, HW21, HW22, HW23 at the same time.Electroplating wastewater with excessive heavy metals belongs to the scope of wastewater pollution prevention and control and is included in the management of wastewater, which does not apply to the scope of the Law of the People's Republic of China on Prevention and Control of Environmental Pollution by Solid Wastes and is not a hazardous waste. Although the excessive wastewater is not included in the management of hazardous waste, according to the "Two High Judicial Interpretations" (2016 version), if the wastewater exceeds the standard of one type of heavy metal (such as lead, mercury, chromium, cadmium, arsenic) by three times, or the standard of two types of heavy metals (such as nickel, copper, zinc, manganese, vanadium) by more than 10 times, in addition to imposing administrative penalties, as usual, they will be held criminally liable.

2. Sludge from domestic sewage treatment plants:
It is a solid waste, not a hazardous waste. According to the Environmental Office [2010] No. 157, this type of waste in the process of transfer management, "reference to the management of hazardous waste, the establishment of sludge transfer joint list system." The reference to hazardous waste management means that this type of sludge does not belong to hazardous waste, but it is necessary to raise the management level, especially to strengthen the management of accounts, to prevent the transport process of spilling, dripping and illegal dumping. However, the sludge generated in the process of sewage treatment in industrial enterprises, often because of its leaching toxicity exceeds the standard, or contains other toxic and hazardous substances and other dangerous characteristics, the vast majority of which should be classified as hazardous wastes (the method of determination is mainly based on the enterprise's environmental assessment, the industry law, the source of the material, the experts identified, the properties of the identification, etc.).

3. Fly ash from domestic waste incineration:
It is a hazardous waste (HW18). However, after meeting the requirements of Article 6.3 in the "Pollution Control Standards for Domestic Waste Landfills" (GB16889-2008), it is not included in the management of hazardous waste to enter the landfill of domestic waste; the other situation is that if after pretreatment, it meets the relevant requirements of the "Pollution Control Standards for the Cooperative Disposal of Solid Waste in Cement Kilns" (GB30485-2013), the process of co-disposal is also included in the Exemptions from management.

Most of them are hazardous waste. The Regulations on the Management of Medical Waste (State Council Decree No. 380) stipulate that "medical waste refers to directly or indirectly infectious, toxic and other hazardous wastes generated by medical and health institutions in the course of medical treatment, prevention, health care and other related activities." Infectious wastes" in the "Classification Catalogue of Medical Wastes" (Health and Medical Development [2003] No. 287) include "other items contaminated by patients' blood, body fluids and excreta", and the slag, sedimentation sludge and septic tank sludge generated in the process of sewage treatment in medical institutions should be treated as "infectious wastes". Grate sludge, sedimentation sludge and septic tank sludge generated in the process of sewage treatment in medical institutions should be included in this category. The waste code in the new National Hazardous Waste List is 841-001-01.
If a healthcare facility has a specially designed wastewater treatment process in its EIA and has made a determination of the properties of the sludge, and if management believes that the sludge should be included in the management of hazardous wastes, a final determination should be made through the hazardous waste identification process.

Five Steps to Identify Sludge as Hazardous Waste

According to the "National Hazardous Waste List" and "Hazardous Waste Identification Criteria - General Principles" issued by the Ministry of Environmental Protection, the National Development and Reform Commission and the Ministry of Public Security, combined with the "Technical Policy on Treatment, Disposal and Pollution Prevention of Urban Sewage Treatment Plant Sludge (for Trial Implementation)" jointly issued by the Ministry of Housing, Ministry of Construction, Ministry of Environmental Protection and the Ministry of Science and Technology on 28th February 2009, the sewage sludge can be determined in five steps Whether sewage sludge is hazardous waste, as shown in the figure below:
Step 1 Classification
Step 2 Basis for judgement
Step 3 How to regulate
Step 4 Resource utilisation
Step 5 What can be exempted?

According to the Ministry of Emergency Management news, the State Council Safety Committee recently issued the National Work Safety Special Remediation Three-Year Action Plan (referred to as the "Three-Year Action Plan") specifies two thematic implementation programmes, nine special remediation implementation programmes, special remediation of the three-year action from the start of April 2020 to the end of December 2022, which includes the organization of a comprehensive investigation of waste hazardous chemicals and other hazardous wastes. These include the organisation of a comprehensive investigation of hazardous wastes such as abandoned hazardous chemicals, with chemical parks and chemical enterprises being the key targets for remediation, and the requirement that the whole process of hazardous waste storage, transport and disposal be regulated and implemented to ensure the safe disposal of hazardous wastes.
As a result, the three-year campaign to specialise in hazardous waste has begun!

Hazardous waste special management is one of the three-year special rectification focus - a special risk prevention and control of hazardous chemicals, will be carried out in four stages.
With regard to the safety and remediation of hazardous wastes, the Three-Year Action Plan indicates several major aspects, such as carrying out hazardous waste investigations, improving hazardous waste management mechanisms and accelerating the construction of hazardous waste disposal capacity. In order to ensure the supervision of hazardous wastes in the whole process, the relevant units should establish and improve the means of control from various aspects:

First, the establishment of a standardised hazardous waste inventory ledger, the classification of hazardous waste into zones for storage, and the setting up of hazardous waste identification markers for collection, storage, transport and disposal, in particular to strengthen the supervision and inspection of chemical parks, chemical and hazardous chemical units, and hazardous waste disposal units within the jurisdiction.

Secondly, the implementation of the hazardous waste declaration and registration system, and will be seriously investigated and dealt with at the same time into the credit management, the implementation of joint disciplinary action; at the same time to establish and improve the transfer of hazardous waste from the generation of disposal of various links in the joint system, the use of information technology, control of the flow of hazardous wastes, and dynamic supervision;

Thirdly, we have established a system of departmental liaison, regional collaboration and consultation and supervision of major cases to form a whole-process supervision system, and have revised and improved the Hazardous Waste Storage and Pollution Control Standards to promote the implementation of relevant laws, regulations and standards and norms by enterprises through rigorous means and close supervision.
Accelerating the construction of hazardous waste disposal capacity is the final link in the treatment of hazardous waste, and should not be overlooked. In this regard, the Three-Year Action Plan proposes that, according to the types and quantities of hazardous wastes generated in the region, reasonable planning should be made for the deployment of disposal enterprises or the use of disposal by enterprises themselves in a variety of ways, so as to strengthen regional hazardous waste disposal capacity, and at the same time to pay attention to high-risk grades of hazardous wastes, in particular to speed up the research and development of comprehensive disposal technology and equipment.

The unit that generates hazardous waste should also develop a hazardous waste management plan and declare to the competent environmental protection department at or above the county level where it is located the type of hazardous waste, the amount generated, the flow direction, the level of danger, the storage facilities, the use of their own disposal facilities or entrusted to an outside unit to use the disposal method and other relevant data and information. It should be noted that the storage of hazardous wastes shall not exceed one year, and it is strictly prohibited to mix hazardous wastes into non-hazardous wastes for storage.

This means that, in the field of hazardous waste treatment, the next may make, revise a number of relevant mandatory national standards, industry standards to regulate enterprises and industrial parks to carry out the management of hazardous waste, prompting China's hazardous waste generation to reduce the amount of treatment capacity has been significantly improved. (Part of the picture source: environmental protection new classroom, edited by net superior hazardous waste)
The total amount of sewage treatment in China is currently about 200 million tonnes/day, which roughly produces a staggering amount of wet sludge of about 200,000 tonnes/day. However, the proportion of its portion properly treated and disposed of is still low. The current situation of sludge treatment and disposal in China is very unpromising.

According to relevant data, about 30 million tonnes of sludge are not properly disposed of out of the large amount of sludge produced in China every year. The previous disposal practice was to send it to landfills. At present, the disposal of sludge is dominated by sludge resource utilisation. Most of the sewage treatment plants in China have a long service life and were constructed earlier, with a low level of synchronised sludge treatment. Due to national as well as local attention, sludge treatment has been incorporated into the sewage treatment process, but it still faces the dilemma of disproportionate production and disposal. On the one hand, the cost of sludge disposal is high; on the other hand, the technical route of sludge disposal is not yet perfect.

With regard to sludge treatment and disposal, China has issued a series of policies and regulations, such as the "Urban Sewage Treatment and Pollution Prevention and Control Technology Policy" and "Pollutant Emission Standards for Urban Sewage Treatment Plants" during the period of 2000-2002; the Ministry of Housing and Construction, the Ministry of Environmental Protection, and the Ministry of Science and Technology jointly issued the "Sludge Treatment and Disposal and Prevention and Control of Pollution Technology Policy (Trial)" in 2009; the Ministry of Environmental Protection introduced the "Sludge Treatment and Disposal In 2010, the Ministry of Environmental Protection issued the "Guidelines on the Best Available Techniques for Sludge Treatment, Disposal and Pollution Prevention and Control", "Technical Specifications for Sludge Treatment and Disposal in Urban Sewage Plants (Draft)", and the Ministry of Housing and Construction issued the "Technical Guidelines for the Treatment and Disposal of Sludge in Urban Sewage Treatment Plants (Trial)", and so on.

CAC membrane composting technology is a major innovation based on aerobic composting technology, CAC membrane composting technology is to add auxiliary materials and microbial decomposition bacterial agent for sludge pretreatment, and then through the CAC functional membrane will be completely covered by the material, the formation of micro-positive pressure within the membrane of the "artificial climate box", through the intelligent control system control of the ventilation and oxygen supply process, to achieve aerobic microbial high temperature fermentation of organic compounds contained in the treated sludge. It can achieve aerobic microbial fermentation at high temperature to deal with the organic compounds contained in the sludge, and the microbial metabolism generates a high temperature of 60°C-70°C for more than 10 days, which can completely kill the pathogenic bacteria, block the emission of odour and stench to the outside environment, and achieve the harmless treatment of the sludge.

In the future, sludge treatment and disposal will be the next pass in the battle against environmental pollution, the next important grip on environmental protection, and the next windfall in the environmental protection market.Sludge Filter Press

So what are the six national standard limits for sludge disposal? And how is sludge disposal categorised? The relevant national standards are collated below:

Pollutant Control Standards for Agricultural Sludge (GB 4284-2018)

This standard specifies the pollutant control indicators, sampling, testing, monitoring and sampling methods when the urban sewage treatment plant for agricultural use. The standard applies to the control of pollutants when urban sewage treatment plant sludge in arable land, garden land and pasture land.Filter Press Manufacturers

When sludge products are used for agricultural purposes, they are classified into Class A and Class B sludge products according to their pollutant concentrations, and their pollutant concentration limits shall meet the requirements of Table 1, and the conditions for the use of Class A and Class B sludge products are as follows.

When sludge products are used for agricultural purposes, their hygienic indicators and limit values shall meet the requirements of Table 3.

When sludge products are used for agricultural purposes, their physicochemical indicators and limit values shall meet the requirements of Table 4.

When sludge products are used for agricultural purposes, the cumulative annual use should not exceed 7.5t/h㎡ (on a dry basis), and the continuous use should not exceed 5 years.

Disposal of sludge from urban sewage treatment plants Mud quality for brick-making (GB/T 25031-2010)

This standard specifies the mud quality, sampling and monitoring of sludge from urban sewage treatment plants for sintering and utilisation. The standard applies to urban sewage treatment plant sludge disposal and sludge system sintered brick use.

When sludge is used to make bricks, the physical and chemical indexes of sludge should meet the requirements of Table 1.

When sludge is used to make bricks, the sludge burning loss and radionuclide index should meet the requirements of Table 2.

When sludge is used to make bricks, the sludge pollutant concentration limits shall meet the requirements of Table 3.

When sludge is used in brick making and crowd contact situations, the sludge hygiene indicators should meet the requirements of Table 4.

Disposal of sludge from urban wastewater treatment plants: Mud quality for separate incineration (GB/T 24602-2009)

This standard specifies the urban sewage treatment plant sludge separate incineration and utilisation of mud quality indicators and limits, sampling and monitoring, etc., the standard applies to urban sewage treatment plant sludge disposal and sludge

Separate incineration for utilisation.

When sludge is separately incinerated and utilised, its physical and chemical indexes and limit values should meet the requirements of Table 1, and the sand content of sludge should be fully considered when selecting the furnace type of incinerator.

Sludge Filter Press

Disposal of Sludge from Urban Sewage Treatment Plants Mud for Land Improvement (GB/T 24600-2009)

This standard specifies the sludge indicators and limits, sampling and monitoring of urban sewage treatment plant sludge land improvement and utilisation. The standard applies to urban sewage treatment plant sludge disposal and sludge

Land improvement use. The quality of the sludge used for land reclamation in drainage pipe pass-through sludge can be referred to this standard.

When sludge land improvement and use, its physical and chemical indicators and limit values should meet the requirements of Table 1.

Nutrient indicators and limit values for sludge land improvement and utilisation shall meet the requirements of Table 2.

The microbiological indicators and limit values of sludge for land improvement and utilisation shall meet the requirements of Table 3.

When sludge land improvement and utilisation, its pollutant indicators and limit values shall meet the requirements of Table 4.

Mud quality for mixed landfill for sludge disposal in urban sewage treatment plants (GB/T 23485-2009)
This standard specifies the urban sewage treatment plant sludge into the domestic waste sanitary landfill mixed landfill disposal and used as mulch soil mud quality indicators and limits, sampling and monitoring. The standard applies to urban sewage treatment plant sludge disposal and sludge and domestic waste mixed landfill.

When sludge is used for mixed landfill, its pollutant indicators and limit values shall meet the requirements of Table 1.

When sludge is used as landfill cover soil additive, its pollutant indicators and limits shall meet the requirements of Table 2, and basic indicators and limits shall meet the requirements of Table 3.

When sludge is used as an additive to landfill final cover soil, its biological indicators must also meet the requirements of GB 18918.

Disposal of sludge from urban sewage treatment plants Mud for landscaping (GB/T 23486-2009)

This standard specifies the urban sewage treatment plant sludge gardening green use of mud quality indicators and limits, sampling and monitoring. The standard applies to urban sewage treatment plant sludge disposal and sludge landscaping use.

When sludge gardening is utilised in population contact situations, the biological indicators and limit values should meet the requirements of Table 3.

When sludge is used in gardening, its pollutant indicators and limit values shall meet the requirements of Table 4.

Classification of Sludge Disposal in Urban Sewage Treatment Plants (GB/T 23484-2009)

Classification of Electroplating Sludge Treatment and Disposal (GB/T 38066-2019)