Selection criteria for sewage treatment processes

The selection criteria for sewage treatment processes mainly include the following aspects:

water quality characteristics

Types of pollutants: Different sewage treatment processes have different removal effects on different types of pollutants. If the wastewater contains a large amount of organic matter, biological treatment method can be used; Wastewater containing heavy metal ions requires the use of chemical precipitation, ion exchange, and other methods to remove heavy metals first.

Pollutant concentration: High concentration organic wastewater may require a combination of anaerobic and aerobic biological treatment processes, while low concentration wastewater may be achievable through simple aerobic or ecological treatment processes.

Biodegradability: Wastewater with good biodegradability should be given priority to biological treatment methods. Otherwise, pretreatment may be necessary to improve its biodegradability, or physical and chemical treatment methods may be the main approach.

Processing Objectives

Emission standards: To meet strict emission standards, such as Class IV and V standards for surface water, advanced treatment processes such as membrane separation and advanced oxidation are often required; If only the general urban sewage treatment plant discharge standards need to be met, conventional secondary treatment processes can usually meet them.

Reuse requirements: For wastewater with reuse needs, such as industrial cooling, urban greening, landscape water replenishment, etc., corresponding treatment processes need to be selected according to different reuse purposes to ensure that the water quality of the reused water meets the usage requirements.

Water volume scale

Large scale sewage treatment plants generally tend to choose processes with mature technology, stable operation, and high treatment efficiency, such as traditional activated sludge process and its improved processes, oxidation ditch, etc., to facilitate centralized management and reduce unit treatment costs.

Small scale sewage treatment facilities: Integrated treatment equipment, biological contact oxidation method, SBR and other processes can be considered, which have the advantages of small footprint, simple operation, and strong flexibility.

Site

Abundant land resources: It is possible to choose some ecological treatment processes that occupy a large area but have stable treatment effects and low operating costs, such as oxidation ponds and artificial wetlands.

Land resources are scarce: priority should be given to processes with small footprint, such as MBR (membrane bioreactor), aerated biofilter, etc.

economic factors 

Construction cost: There are significant differences in construction investment for different sewage treatment processes. The MBR process has relatively high construction costs due to its high equipment and membrane component costs; The construction cost of traditional activated sludge process is relatively low.

Operating costs: including energy consumption, chemical consumption, equipment maintenance, and other aspects. For example, anaerobic biological treatment processes have lower energy consumption, but may require the addition of some special nutrients; The energy consumption of aerobic biological treatment process is relatively high, especially the energy consumption of aeration system accounts for a large proportion.

environmental factor

Climate conditions: In cold regions, it is necessary to choose processes suitable for operating in low-temperature environments or take effective insulation measures to ensure treatment effectiveness. For example, insulation treatment can be applied to structures such as aeration tanks, or low-temperature resistant microbial strains can be selected.

Sensitivity level of surrounding environment: If the sewage treatment plant is located near residential areas or environmentally sensitive areas, it is necessary to consider the impact of noise, odors, and other factors generated during process operation on the surrounding environment. Low noise and low odor discharge processes should be selected as much as possible, such as using underground or semi underground sewage treatment facilities and strengthening deodorization measures.

management level

Strong technical strength: Some relatively complex and highly automated processes can be selected, such as A2/O (anaerobic anoxic aerobic) process, MBR process, etc., which can better leverage their processing advantages, but require professional technical personnel for operation and maintenance.

If the management level is limited, it is advisable to adopt simple and easy to operate processes, such as biological turntables, stabilization ponds, etc. These processes have relatively low technical requirements for operators and are more convenient for operation and management.