Basic methods and treatment process of sewage treatment（污水处理的基本方法及处理流程）The basic methods of sewage treatment mainly include physical methods, chemical methods, biological methods, and combined processes. The treatment process is divided into primary, secondary, tertiary treatment, and deep treatment according to the treatment objectives and water quality requirements. Here is a detailed introduction:
1、 Basic methods of sewage treatment
Physical Law
Principle: Separate suspended solids, floating particles, etc. in sewage through physical action.
Common methods:
Grille filtration: removes large suspended particles (such as tree branches, plastic bags).
Sedimentation: Using gravity to settle suspended solids (such as in primary and secondary sedimentation tanks).
Air flotation: Separation of suspended matter by floating up through the adsorption of microbubbles.
Filtration: sand filtration, membrane filtration, etc., to further remove small particles.
Characteristics: It does not change the chemical properties of pollutants, is easy to operate, but cannot remove soluble pollutants.
Chemical method
Principle: Remove dissolved pollutants from wastewater through chemical reactions.
Common methods:
Neutralization: Adjust the pH value of wastewater to neutrality.
Coagulation: Adding coagulants (such as polyaluminum chloride) to cause colloidal particles to aggregate and settle.
Redox: Using oxidants such as ozone and chlorine to decompose toxic substances.
Characteristics: High processing efficiency, but may generate chemical sludge, requiring subsequent treatment.
Biological Law
Principle: Utilize microbial metabolism to degrade organic matter and nutrients.
Common methods:
Activated sludge process: Adsorption, oxidation and decomposition of pollutants by suspended microbial communities (activated sludge).
Biofilm method: Microorganisms attach to the surface of a carrier to form a biofilm, which adsorbs and oxidizes pollutants.
Anaerobic biological treatment method: Under anaerobic conditions, anaerobic bacteria decompose organic matter into methane, carbon dioxide, etc.
Features: Low processing cost, good environmental friendliness, but requires control of microbial growth conditions.
Combination process
Principle: Combining multiple treatment methods to improve treatment efficiency and water quality.
Common processes:
MBR process: Membrane bioreactor, combining biodegradation and membrane separation technology, produces excellent effluent quality.
A ²/O process: anaerobic anoxic aerobic process, which can simultaneously remove organic matter, nitrogen, and phosphorus.
Features: High processing efficiency, stable effluent quality, but high investment and operating costs.
2、 Sewage treatment process
The sewage treatment process is usually divided into primary treatment, secondary treatment, tertiary treatment, and advanced treatment according to the treatment objectives and water quality requirements.
First level processing (preprocessing)
Purpose: To remove large suspended and floating particles and regulate water quality and quantity.
Main facilities:
Grille: intercepts large suspended particles.
Sand settling tank: removes inorganic particles such as sand particles.
Regulating pool: Balancing water quality and quantity to provide stable conditions for subsequent treatment.
Outlet water quality: SS removal rate is about 50%, BOD removal rate is about 20% -30%.
Secondary treatment (biochemical treatment)
Objective: To remove dissolved organic matter and nutrients (such as nitrogen and phosphorus).
Main methods:
Activated sludge process: maintains high concentration of microorganisms through aeration to degrade organic matter.
Biofilm method: Microorganisms attach to the surface of a carrier, forming a biofilm to degrade pollutants.
Outlet water quality: BOD removal rate exceeds 90%, SS removal rate exceeds 90%, which can meet general discharge standards.
Third level processing (deep processing)
Purpose: To further remove recalcitrant organic matter, nutrients, microorganisms, etc., and meet higher emission or reuse requirements.
Main methods:
Coagulation precipitation: Adding coagulants causes colloidal particles to aggregate and settle.
Filtration: sand filtration, membrane filtration, etc., to remove small particles.
Disinfection: Chlorination, ozone oxidation, etc., to kill pathogenic microorganisms.
Outlet water quality: It can meet high standards for surface water discharge and reclaimed water reuse.
Deep processing (optional)
Purpose: To deeply purify specific pollutants, such as heavy metals, toxic and harmful substances, etc.
Main methods:
Activated carbon adsorption: removes difficult to degrade organic matter, odors, etc.
Ion exchange: Removing heavy metal ions.
Membrane separation technology: such as reverse osmosis, nanofiltration, etc., to achieve high-purity water reuse.
3、 Summary
The basic methods of sewage treatment include physical methods, chemical methods, biological methods, and combined processes. The treatment process is divided into primary treatment, secondary treatment, tertiary treatment, and deep treatment according to the treatment objectives and water quality requirements. By selecting appropriate treatment methods and processes, efficient sewage treatment and water resource recycling can be achieved.
污水处理的基本方法主要包括物理法、化学法、生物法以及组合工艺，其处理流程则根据处理目标和水质要求，分为一级、二级、三级处理及深度处理。以下是详细介绍：
一、污水处理的基本方法
物理法
原理：通过物理作用分离污水中的悬浮物、漂浮物等。
常见方法：
格栅过滤：去除大块悬浮物(如树枝、塑料袋)。
沉淀：利用重力使悬浮物沉降(如初沉池、二沉池)。
气浮：通过微气泡吸附悬浮物上浮分离。
过滤：砂滤、膜过滤等，进一步去除微小颗粒。
特点：不改变污染物化学性质，操作简单，但无法去除溶解性污染物。
化学法
原理：通过化学反应去除污水中的溶解性污染物。
常见方法：
中和：调节污水pH值至中性。
混凝：投加混凝剂(如聚合氯化铝)使胶体颗粒凝聚沉降。
氧化还原：利用氧化剂(如臭氧、氯气)分解有毒物质。
特点：处理效率高，但可能产生化学污泥，需后续处理。
生物法
原理：利用微生物代谢作用降解有机物和营养盐。
常见方法：
活性污泥法：通过悬浮生长的微生物群体(活性污泥)吸附、氧化分解污染物。
生物膜法：微生物附着在载体表面形成生物膜，通过吸附、氧化分解污染物。
厌氧生物处理法：在无氧条件下，厌氧菌将有机物分解为甲烷、二氧化碳等。
特点：处理成本低，环保性好，但需控制微生物生长条件。
组合工艺
原理：结合多种处理方法，提高处理效率和水质。
常见工艺：
MBR工艺：膜生物反应器，结合生物降解与膜分离技术，出水水质优。
A²/O工艺：厌氧-缺氧-好氧工艺，可同时去除有机物、氮、磷。
特点：处理效率高，出水水质稳定，但投资运行成本较高。
二、污水处理流程
污水处理流程通常根据处理目标和水质要求，分为一级处理、二级处理、三级处理及深度处理。
一级处理(预处理)
目的：去除大块悬浮物、漂浮物，调节水质水量。
主要设施：
格栅：拦截大块悬浮物。
沉砂池：去除砂粒等无机颗粒。
调节池：均衡水质水量，为后续处理提供稳定条件。
出水水质：SS去除率约50%，BOD去除率约20%-30%。
二级处理(生化处理)
目的：去除溶解性有机物、营养盐(如氮、磷)。
主要方法：
活性污泥法：通过曝气维持高浓度微生物，降解有机物。
生物膜法：微生物附着在载体表面，形成生物膜降解污染物。
出水水质：BOD去除率超90%，SS去除率超90%，可满足一般排放标准。
三级处理(深度处理)
目的：进一步去除难降解有机物、营养盐、微生物等，满足更高标准的排放或回用要求。
主要方法：
混凝沉淀：投加混凝剂使胶体颗粒凝聚沉降。
过滤：砂滤、膜过滤等，去除微小颗粒。
消毒：氯化、臭氧氧化等，杀灭病原微生物。
出水水质：可满足地表水体排放、中水回用等高标准要求。
深度处理(可选)
目的：针对特定污染物进行深度净化，如重金属、有毒有害物质等。
主要方法：
活性炭吸附：去除难降解有机物、异味等。
离子交换：去除重金属离子。
膜分离技术：如反渗透、纳滤等，实现高纯度水回用。
三、总结
污水处理的基本方法包括物理法、化学法、生物法以及组合工艺，处理流程则根据处理目标和水质要求，分为一级处理、二级处理、三级处理及深度处理。通过合理选择处理方法和流程，可实现污水的高效处理和水资源的循环利用。
