at present, there are still a few areas that only focus on sewage treatment plants and tailwater discharge, but pay little attention to sewage network facilities. improving sewage collection rate is a prerequisite for improving sewage treatment capacity and level in an all-round way. it is an important basis for reducing the total amount of pollutants discharged, and a basic guarantee for achieving stable, better and progressive improvement of water environmental quality.
recently, environmental quality bulletins of 2018 have been published in various regions. in addition to publishing environmental quality indicators, sewage treatment status has also been announced in some regions. from the data point of view, the centralized treatment rate of urban sewage in most places is more than 80%, some even as high as 95%. however, after consulting the contents of many local bulletins, the author found that at present, little mention has been made of the urban sewage collection rate.
so, if the centralized treatment rate of urban sewage is higher, does it mean that the impact of sewage on the external environment is weakened and reduced? in fact, in some cities and towns, if the water body stagnates for several days, the water quality will often decline significantly, and even the phenomenon of black and odor return occurs. the reason is that the sewage collection rate is not high. if the rate of domestic sewage collection is not up or the proportion of sewage collection is too low, there are still a large number of sewage discharged directly or indirectly into the river, so the deterioration of water quality becomes inevitable.
therefore, avoiding sewage collection rate, only discussing sewage treatment rate, collection treatment rate or centralized treatment rate, or even claiming that the tail water of sewage treatment plant has been marked to the surface water class iv standard, can not fully represent the fundamental improvement of water quality.
of course, accurate calculation of urban domestic sewage collection rate is indeed more complex, among which there are many uncertain interference factors. for example, the discharge coefficient of domestic sewage in different areas is different, and the phenomenon of rain-sewage pipe-in-pipe and river water back-irrigation exists in different places to varying degrees. in a few places, the amount of sewage treatment and the supply of tap water are completely disproportionate, and the difference is significant. in some places, even though the two data are relatively matched, the concentration of influent index of sewage treatment plant is too low, which also indicates that the pipeline network is seriously damaged, and rainwater or river water has entered the sewage network. therefore, when discussing the sewage treatment rate, we should not only avoid the sewage collection rate, but also take the collection rate as the pre-factor.
sewage collection rate is a direct reflection of the implementation of the measures of pollution control and interception. in recent years, many places have gradually realized the influence and restriction of sewage collection rate on deepening water pollution prevention and control. we will continue to increase financial and material input and strengthen the capacity-building of sewage pipelines and sewage treatment. in some areas, the old and old pipeline networks are also inspected, and the wrong, leaky and mixed junctions of the repaired pipeline networks are inspected in an all-round way, and remarkable results have been achieved in water control.
however, the author found that at present, there are still a few areas only focus on sewage treatment plants and tail water discharge, but the importance of sewage network facilities is not high, the construction progress is not fast enough, and the effect is not good enough. in some places, although the task of sewage network construction has been implemented every year, it is still difficult to clarify the current situation of sewage collection, and the rate of urban sewage collection is often estimated. the unclear background of the household, resulting in sewage treatment is only a general situation, precise water treatment is undoubtedly discounted.
improving sewage collection rate is a prerequisite for improving sewage treatment capacity and level in an all-round way. it is an important basis for reducing the total amount of pollutants discharged, and a basic guarantee for achieving stable, better and progressive improvement of water environmental quality. therefore, sewage treatment should not only pay attention to the treatment rate but also neglect the collection rate. mutual consideration should be given to each other, the priority should be weighed, strengths and weaknesses should be strengthened to ensure that sewage should be collected and treated effectively. in this regard, the author has two suggestions for reference.
on the one hand, the status of sewage collection should be taken as an important indicator and regular assessment and publicity should be organized. to give full play to the role of the assessment baton, the assessment index of increasing the number of kilometers of sewage pipe network every year should be optimized and adjusted. focus on the assessment of sewage collection rate to increase the proportion of results-oriented forced sewage network construction. because the calculation of sewage collection rate is relatively complicated and the accuracy is difficult to grasp, it is suggested to adopt a more convenient way to calculate, such as using the cod index of urban sewage treatment plant and the amount of domestic sewage to verify the urban sewage collection rate.
in addition, to give full play to the role of public supervision, provincial and municipal governments should announce the progress of sewage network construction and sewage collection in various places every year, so that the masses can make judgements, and urge the territorial governments to find out the shortcomings, self-pressure, and make further efforts.
on the other hand, the capacity of sewage collection should be taken as an important part to strengthen the construction and repair of pipeline network. local governments should give priority to infrastructure construction, such as sewage pipe network, in combination with urban development planning, so as to ensure local social development. when building a new sewage supervisor, it is necessary to strengthen the construction of branch pipes, focusing on taking over and entering the household, so as to prevent the supervisor from being idle when completed. in addition, it is suggested that new pipeline networks should not be buried underground, and open pipelines or galleries should be constructed in areas where conditions are available so as to find faults in time and maintain them in time in the future.
for the running sewage pipe network, we can not feel buried in the ground can not be seen, let it be at its own convenience. in fact, many areas can not collect sewage, the main crux is that a large number of sewage pipelines are out of repair for a long time, and the phenomenon of leakage of sewage is serious.
therefore, it is necessary to adopt advanced technology, periodic system screening and repair if necessary.
if the effect is not guaranteed after repairing or repairing, we must make up our minds to lay new sewage pipelines and eradicate the problem.
