How will sewage treatment standards and technology develop?

● In the future, the WWTP will not only consider the current life and industrial wastewater problems, but also consider the treatment and operational challenges brought about by the subsequent inclusion of post-rainwater.
● From the eutrophication control of water bodies, the total phosphorus index is the first, ammonia nitrogen is the second, total nitrogen is the third, and these three indicators are controlled. The conventional indicators of sewage discharge control
● There may be various combinations of processes in the future that will benefit the development of the wastewater treatment business. Enterprises, research institutes, etc. can all use their imagination to make use of their own resources and try different things.
With the continuous development of the sewage treatment industry, sewage treatment technology facilities are changing from the traditional to the reform. In the future, the changes in the industry will become more apparent. Zheng Xingcan, chief engineer of the China Urban Design Engineering North China Research Institute, has been studying the development trend of wastewater treatment in recent years. He analyzed the possible changes in wastewater treatment scale, standards, and technology.
Reporter: There are currently more than 4,000 sewage treatment plants in China. The treatment rate is close to 90%. Will there be growth in quantity and scale in the future? What will change?
Zheng Xingcan: In simple terms, there will be an increase in the number. I personally expect to approach 5,000 by the end of this year, by 10,000 by 2020, and by 20,000 by 2030. Of course, the number of WWTPs is increasing, but the increase in the overall scale of growth is not linear, which means that the scale of the subsequent WWTPs may become smaller and smaller.
I think that between 2020 and 2030, sewage treatment facilities will have an important feature that they will incorporate rainwater, especially early rainwater treatment, which will lead to at least 50% expansion of large-scale sewage treatment plants in many cities. Of course, to be fully realized, this process may take 20 to 30 years or even longer.
We estimate that around 2020, some cities will take the lead in practice. Therefore, the sewage treatment plant will not only consider the current life and industrial wastewater problems in the future, but also consider the treatment and operation challenges brought by the future inclusion of rainwater.
Reporter: At present, urban sewage treatment plants have a relatively large single scale. They are focusing on processing routes. They have encountered difficulties in the management of pipeline networks and reuse. What are the trends in the future?
Zheng Xingcan: I think that a large part of the new sewage treatment facilities in the future will be in villages and towns, and the scale will not be large. However, because of its small scale, on the one hand it brings some new opportunities for new technology applications, and on the other hand, it also brings business opportunities for new innovative small and medium-sized companies.
However, in the long run, small facilities of tens or hundreds of tons will not be able to exist for a long time, and sooner or later they will merge. For example, Austria's sewage treatment facilities are a combination of more than a dozen small cities and towns with sewage treatment. Several towns share funds and build a sewage treatment plant. I believe that this trend will also occur in China.
Reporter: Not long ago, the relevant departments solicited opinions on the revision of the "Emission Standards for Urban Wastewater Disposal," and all indicators were tightened. COD in special areas even proposed to reach 30mg/L. Is this tightening a future trend?
Zheng Xingcan: First of all, any environmental issue is related to the economy. What kind of investment must be made in designing what kind of emission level to achieve.
Second, the non-biodegradable COD in the effluent will not cause black odor in the water if it is a natural substance. Therefore, if the COD requirement is forcibly reached a level of 20mg/L, especially in the case of higher and higher concentrations of sewage inflows in the future, such high standards are injures to the people.
I think that for our current sewage treatment technology, there is an indicator that is even more critical, namely the ammonia nitrogen index, which is directly related to black and odor eutrophication. Moreover, if the effluent ammonia nitrogen index can be lower than 1mg/L litre, the relevant COD, BOD will meet the corresponding requirements.
In terms of total phosphorus and total nitrogen, I have some differences with some domestic experts. In my opinion, if the goal is to control the growth and eutrophication of algae, then the relationship between nitrogen and phosphorus must be emphasized. Total nitrogen is lower, and if total phosphorus does not change, then it will not solve the problem.
From this point of view, total phosphorus is the number one in terms of eutrophication control of water bodies, ammonia nitrogen is the second, total nitrogen index is the third, and these three indicators are controlled, and the conventional indicators of sewage discharge are controlled. Living.
Reporter: In view of the increasingly complex and stringent requirements, can the current process based on the activated sludge process be able to cope? What are the trends in the future?
Zheng Xingcan: Regardless of how the process changes, stabilizing standards, energy, resources, and low-carbon and low-cost consumption, I think that in the short term, there will be no change.
In terms of phosphorus and nitrogen removal, it is a big challenge for conventional processes to turn to anaerobic ammonia oxidation. At present, the sidestream is relatively mature, and the mainstream process still needs to do work. As far as I know, there are already five or six teams working in this area. Some companies even proposed the goal of achieving mainstream anaerobic ammonia oxidation within two years. I think this goal is a bit high.
There are several problems that cannot be avoided in the research and application of the process. For example, the urban sewage water quality and quantity have great changes in space and time, the carbon-nitrogen ratio of urban sewage is generally low, the influent inorganic suspended solids are generally high, and the low water temperature and a large number of industrial wastewater, etc., are all very important impacts of domestic sewage treatment. factor.
How to effectively integrate new processes into existing process systems is a very important issue. It is possible that there will be a variety of process combinations in the future, which will be conducive to the development of the sewage treatment business. Enterprises, scientific research institutions, etc. can exert their imaginations and use their own resources to make different attempts.