From the overall perspective, improving the water ecological environment is a systematic project, and the "bid" of the wastewater treatment plant is not a complete solution to the problem. We should pay attention and financial support to ensure the good construction and operation of the sewage treatment plant, and complete the upgrading and upgrading of the standard. A series of supporting policy measures are needed to ensure that all sewage is properly treated.

Since November 4, 2015, the urban sewage treatment plant pollutant discharge standard (draft) "(hereinafter referred to as the" draft ") since its launch, the discussion of the industry has been, in particular discharge limits, and the water environment quality standard are close and connected, is more controversial.

Many in the industry believe that special emission standards have been set up separately from the solicitations, taking into account the environmental and economic differences between different regions. At the same time, new remobilised emerging contaminants such as control project (polychlorinated biphenyl, dioxin and atrazine, etc.), and put forward the specific indicators of sludge innocuity requirements, fully embodies the progress of our country's environmental management. But there are also some questions to ponder.

It should be more scientific.

It is necessary to carry out scientific environmental risk assessment to determine the rationality of limit setting. The daily mean, the average of 7 days, the average of 30 days, which is more suitable for our country, how does the quantity of different scale monitoring sampling make it worth thinking about?

As can be seen from the draft, the number of pollutant indicators under control is significantly higher than that of the eu and us federal standards; At the same time, COD, BOD5, SS, TN, TP and consistency index, and heavy metals, microbial indicators, organic pollutants such as emission limits set also has reached or even exceeded the level of developed countries.

For example, if the COD<30mg/L is required in the draft, how much will it affect the improvement of the environment by reducing the amount of COD in the water to 30mg/L from 60mg/L? What is the environmental negative effect caused by technological transformation and increasing electricity consumption to dispose of this part of COD? It is necessary to carry out scientific environmental risk assessment to determine the rationality of limit setting.

At the same time, for TN, ammonia nitrogen and other indicators, from the perspective of control eutrophication and water treatment processes, TN meet emissions standards, under the condition of ammonia nitrogen will be up to standard, and ammonia nitrogen in water converted into various forms of nitrogen, thus to control the meaning of ammonia nitrogen is up for debate.

The effluent water quality of sewage treatment plant is affected by the fluctuation of water inlet load, temperature change and operation failure. Reference in the draft the monitoring method of some European countries, based on, "in view of the above the international practice, the new standard sampling frequency requirements of continuation of the current standard of water pollutants, namely the 24 hour time proportion mix sample, daily average meter".

However, the study found that the eu determines the sample size according to the size of the wastewater treatment plant, while stipulating that the number of water samples should be allowed to exceed the standard. Meanwhile, the annual mean of TN and TP is implemented. Germany also adopted the instantaneous sample, but provided that one of the five water samples was allowed to exceed the standard (less than 100% of the standard value). The United States fully considers the impact load capacity of small sewage treatment plants. For CBOD5 and TSS in the secondary treatment standard, the average concentration of 30 days and the average concentration limit of 7 days are set.

And partial sewage treatment plant reflects, in our country supervision and inspection, also have the phenomenon that USES instantaneous sample to exceed standard namely. In the monitoring, the daily mean, the average of 7 days and the average of 30 days are more suitable for our country. How do the quantities of different scale monitoring samples be developed? Are the monitoring methods of different indicators consistent? These are worth rethinking in setting standards.

In addition, in the draft, emission limit value is given priority to with concentration index, hard to avoid the enterprise to reduce pollutants concentration dilution standards of behavior, even it is difficult to effectively control the amount of pollutants into the environment.

We should take a long view and be realistic.

The balance between input and output should be evaluated scientifically; Fully consider the impact on the water and surrounding environment; To strengthen the responsibility and authority of local emission standards; Emission standards shall be combined with the discharge permit system.

We have the following Suggestions for the revision of pollutant discharge standards for urban wastewater treatment plants at the national level:

Standards must have a long-term strategic perspective to lead the industry to a more sustainable direction. In combined water environment at the same time, the quality objectives of the wastewater discharge standards and the development of sewage treatment technology must be complementary to each other, sensitive of eutrophication control of water, water reuse, control energy consumption, resource recovery and technological innovation is the key to be overcome and the direction of future development.

Scientific assessment, multi-pronged. Water environmental situation is very serious, but still not blindly set too strict standards, need to input and output of scientific assessment of the balance, then later extreme situations to cut down a little bit of pollution load, relevant into negative effects to the environment may be greater than the environment is produced by cutting load effect. Pollution control needs to be managed from the aspects of deepening basin management, preventing and controlling industrial pollution, controlling surface pollution, construction of rain sewer network and strict environmental supervision.

The standard formulation should follow the three principles of "sustainable and environment-friendly, technological and economic reasonableness, based on scientific basis". Fully consider the influence of the water and surrounding environment to make the effluent of sewage treatment plant an important source of reclaimed water; Adapt to the technological route of selection; Standard limit must be on the water environment capacity, emission intensity and change trend, water function change trend and the different situation of water environment of self-purification ability of science comprehensively on the basis of combining technology of economy and the environment to scientific setting, especially for some emerging pollutants, first based on doing a lot of scientific research, and standards.

Classify and guide, seek truth from facts. In the implementation process of specific standards, it is necessary to take into account the differences of different environments, economic conditions and the actual conditions of the technological level, and seek truth from facts. Refer to foreign practices at the management level and set different levels. At the national level, only the most basic standards and standard formulation methods and systems should be formulated, and the responsibilities and authorities of local emission standards should be strengthened. Local standards should be set locally according to local conditions.

Institutional cohesion, synchronous advance. At the same time, the emission standards should be combined with the emission permit system. In a sense, the emission permits must first be used to provide the necessary data and information sources for the development of emission standards. Moreover, the formulation of emission standards should be synchronized with the standards of water environment quality standards, pollutant discharge standards, detection and evaluation methods, etc.