Sewage refers to the wastewater discharge by people in daily life activities. This kind of wastewater is mainly polluted by waste and human excrement. The quantity, composition and concentration of pollutants are related to people’s living habits and water consumption. Domestic sewage generally does not contain toxic substances, but it has conditions suitable for microbial reproduction. It contains a large number of bacteria and pathogens, and is harmful to a hygienic point of view. The physical processing of wastewater is to separating and recovering undissolved suspended state pollutants (including oil film and oil beads) in the wastewater by physical action can be classified into gravity separation method, centrifugal separation method, and sieve filtration retention method. The processing unit belonging to the gravity separation has sedimentation floating (air floatation), etc. And the corresponding processing equipment’s are grit chambers, sedimentation tanks, grease traps, air floatation tanks and their attachments. The centrifugal separation method itself is a treatment unit and the treatment devices used are a centrifugal separator and a water separator. The screening and retention method has two processing units: grid screening and filtration. The former uses a processing device for the grid and the screen, while the latter uses a sand filter and a microfilter. The processing method based on the principle of heat exchange also belongs to the physical processing method, and the processing unit has evaporation crystallization. There is chemical treatment as well, it separates and removes waste water from dissolved or colloidal conditions in wastewater or convert it into harmless substances. In the chemical treatment method, the processing units based on the chemical reaction generated by the dosing agent are: coagulation, neutralization, redox, etc. And the mass transfer-based treatment units are: extraction, stripping, adsorption, ion exchange, electrodialysis and reverse osmosis. The latter two processing units are also collectively referred to as membrane separation techniques. The processing unit using mas transfer has both chemical and physical effects, so it can be separated from chemical treatment method and become another physical method.
Nowadays, the wastewater treatment infrastructure has got many problems. The first one is that the facilities are getting aging. There are many equipment that have no time for maintenance and care, and some machines have reached the end of retirement age like cars, but government keep continue to use them because of insufficient funds. It will also lead to consequence that wastewater after treated can’t meet the standards. Some wastewater treatment equipment consumes a lot of energy, which will cost the government a lot of money. We need to build a recycling station that can recycle the energy or resources after treatment, which meets goals with the SDG, sustainable development and reuse of energy. Also, a large number of settled populations match with the certain limited wastewater treatment plants. There are travellers and accommodates and more foreign populations. Those people would required more wastewater treatment plants. The wastewater system will become unbalanced so it won’t work sufficiently.
Lack of unified planning and poor comprehensive coordination ability will cause a significant affect in the water treatment efficiency of urban infrastructure. Due to the lack management and connection between different blocks（area）, it is difficult to quickly adjust and effectively connect the infrastructure such as water supply and drainage, energy resourse and transportation between them. The development of wastewater treatment has slowed down and the comprehensive benefits have not been fully utilized.
Another problem that we are facing is the wastewater after recycled by using physical or chemical method, is not able to recycle into a good quality water that people can’t drink. The recycled water is discharged into river. We should find a way the recycled water can be used for commercial. So that we can make recycled water as the second water resources. the processing treatment method should be improved as well so that we can get healthier water resources.
Solution: Lift the maintenance water treatment machine and replace the parts regularly. Just like a car, you have to send it to 4s store to maintain maximum performance. Use more funds to improve technology and achieve energy savings to achieve long-term profit and environmental protection. The key to the improve wastewater treatment technology is to train or solicit professional wastewater engineers. The wastewater treatment technology is constantly being updated every day, especially base on the rapid development of information technology, and the renewal of wastewater treatment technology must keep up in progress all times. Another important point is that government leaders should pay attention to the protection of the ecological environment and set up the rules or policy so that the recommended water management can continue.
Finally, there are still many problems in wastewater infrastructure; it will affect people’s drinking water, causing pollution to the environment, wasting energy and causing economic damage. In future, wastewater management is more and more important in urban infrasturcure.
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