The following factors should be considered in the selection of treatment process.

1.废水水质生活污水水质通常比较稳定，一般的处理方法包括酸化、好氧生物处理、消毒等。而工业废水应根据具体的水质情况进行工艺流程的合理选择。特别需要指出的是，对于采用好氧生物处理工艺处理废水来说，要注意废水的可生化性，通常要求COD/BOD5>0.3，如不能满足要求，可考虑进行厌氧生物水解酸化，以提高废水的可生化性，或是考虑采用非生物处理的物理或化学方法等。

1. Wastewater quality The quality of domestic sewage is generally stable, and the general treatment methods include acidification, aerobic biological treatment, disinfection, etc. Industrial wastewater should be reasonably selected according to the specific water quality. In particular, for the aerobic biological treatment process of wastewater, attention should be paid to the biodegradability of wastewater, which usually requires COD/BOD5> 0.3. If the requirements cannot be met, anaerobic biological hydrolysis acidification can be considered to improve the biodegradability of wastewater, or non biological treatment physical or chemical methods can be considered.

2.污水处理程度这是污水处理工艺流程选择的主要依据。污水处理程度原则上取决于污水的水质特征、处理后水的去向和污水所流入水体的自净能力。但是目前，污水处理程度的确定主要依从国家的有关法律制度及技术政策的要求。通常环境管理部门是根据《污水综合排放标准》及相关的行业排放标准来控制污水的排放浓度，一些经济发展水平较高的地区还规定了更为严格的地方排放标准。因此，无论是何种需要处理的污水，也无论是采取何种处理工艺及处理程度，都应以处理系统的出水能够达标为依据和前提。按照法律、法规、政策的要求预防和治理水体环境污染。

2. The degree of sewage treatment is the main basis for the selection of sewage treatment process. In principle, the degree of sewage treatment depends on the water quality characteristics of sewage, the destination of treated water and the self purification capacity of the water body into which sewage flows. However, at present, the determination of sewage treatment degree is mainly subject to the requirements of relevant national legal systems and technical policies. In general, the environmental management department controls the discharge concentration of sewage according to the Integrated Wastewater Discharge Standard and relevant industrial discharge standards. Some regions with higher economic development level also set stricter local discharge standards. Therefore, no matter what kind of sewage needs to be treated, and no matter what treatment process and degree of treatment are adopted, it should be based on and premise that the effluent of the treatment system can reach the standard. Prevent and control water environment pollution according to the requirements of laws, regulations and policies.

3.建设及运行费用考虑建设与运行费用时，应以处理水达到水质标准为前提条件。在此前提下，工程建设及运行费用低的工艺流程应获得重视。此外，减少占地面积也是降低建设费用的重要措施。

3. When considering the construction and operation costs, the precondition for the construction and operation costs is that the treated water meets the water quality standards. On this premise, attention should be paid to the process flow with low construction and operation costs. In addition, reducing the floor area is also an important measure to reduce construction costs.

4.工程施工难易程度工程施工的难易程度也是选择工艺流程的影响因素之一。如地下水位高，地质条件差的地方，就不适宜选用深度大、施工难度高的处理构筑物。

4. The degree of difficulty of engineering construction is also one of the factors affecting the selection of process flow. If the groundwater level is high and the geological conditions are poor, it is not suitable to select the treatment structures with large depth and high construction difficulty.

5.当地的自然和社会条件

5. Local natural and social conditions

当地的地形、气候等自然条件也对废水处理流程的选择具有一定影响。如当地气候寒冷，则应采用在采取适当的技术措施后，在低温季节也能够正常运行，并保证取得达标水质的工艺。

The local terrain, climate and other natural conditions also have a certain impact on the selection of wastewater treatment process. If the local climate is cold, the process that can operate normally in low temperature season after taking appropriate technical measures shall be adopted to ensure that the water quality reaches the standard.

当地的社会条件如原材料、水资源与电力供应等也是流程选择应当考虑的因素之一。

Local social conditions, such as raw materials, water resources and power supply, should also be considered in process selection.

5.污水的水量除水质外，污水的水量也是影响因素之一。对于水量、水质变化大的污水，应首先考虑采用抗冲击负荷能力强的工艺，或考虑设立调节池等缓冲设备以尽量减少不利影响。

5. In addition to water quality, the quantity of sewage is also one of the influencing factors. For sewage with large changes in water quantity and quality, the process with strong impact load resistance shall be considered first, or buffer equipment such as regulating tank shall be considered to minimize adverse effects.

6.7.处理过程是否产生新的矛盾

6.7. Whether there are new contradictions in the process of handling

污水处理过程中应注意是否会造成二次污染问题。例如制药厂废水中含有大量有机物质(如苯、甲苯、溴素等)，在曝气过程中会有有机废气排放，对周围大气环境造成影响；化肥厂造气废水在采用沉淀、冷却处理后循环利用，在冷却塔尾气中会含有氰化物，对大气造成污染；农药厂乐果废水处理中，以碱化法降解乐果，如采用石灰做碱化剂，产生的污泥会造成二次污染；印染或染料厂废水处理时，污泥的处置为关键考虑的问题。

Attention shall be paid to whether secondary pollution will occur during sewage treatment. For example, pharmaceutical wastewater contains a large amount of organic substances (such as benzene, toluene, bromine, etc.), and organic waste gas will be discharged in the process of aeration, which will affect the surrounding atmospheric environment; The waste water from the gasification of the fertilizer plant is recycled after sedimentation and cooling treatment. The tail gas of the cooling tower will contain cyanide, which will pollute the atmosphere; In the wastewater treatment of pesticide factory, dimethoate is degraded by alkalization method. If lime is used as alkalization agent, the sludge generated will cause secondary pollution; Sludge disposal is a key consideration in wastewater treatment of printing and dyeing or dye plants.

总之，污水处理流程的选择应综合考虑各项因素，进行多种方案的技术经济比较才能得出结论。

In a word, the selection of sewage treatment process should comprehensively consider various factors, and a conclusion can be drawn only through technical and economic comparison of various schemes.