Traditional process of township sewage treatment?

This paper discusses the application of traditional A/O, A/A/O and improved AAO processes in township decentralized sewage treatment and the development of integrated sewage treatment technology, analyzes the advantages and disadvantages of traditional processes in township decentralized sewage treatment, expounds the development of integrated sewage treatment technology, and puts forward research suggestions on the application of integrated sewage treatment technology in township sewage treatment with low carbon and nitrogen ratio, which provides reference for developing simple, reliable, efficient, energy-saving and environmental-friendly integrated sewage treatment technology.

Due to the dispersion and small scale of urban sewage, the traditional raw sewage treatment process requires higher infrastructure and technology of the pipe network, which leads to the pollution of urban sewage to the rural environment. Township decentralized sewage treatment has become another hot spot after traditional sewage treatment, and its treatment effect will affect the treatment effect and ecological environment of black and odorous water bodies in China. Therefore, it is of great significance to develop a sewage treatment process suitable for villages and towns to improve the living environment in the process of urbanization.

1 overview of township sewage treatment

Characteristics of township sewage in 1. 1

Village sewage mainly includes domestic sewage, aquaculture wastewater, drainage from schools, hospitals, service institutions and various public facilities, as well as some industrial wastewater and rainwater. It has the following obvious characteristics [1]. (1) The proportion of domestic sewage is large, and the water quality is uneven due to local living habits, environmental management, perfect facilities and other factors. (2) The population of villages and towns is relatively small, and the amount of sewage is small and scattered, unstable and difficult to collect; The different social needs of the market for a certain industry or product will also affect the change of wastewater quantity; Affected by rainy season and water consumption, the coefficient of water change is large. (3) The main pollutants are TOC, TN and TP. Domestic sewage contains a lot of nitrogen and phosphorus, and the concentration of organic matter is relatively low, so it is a typical sewage with low carbon-nitrogen ratio.

1.2 summary of village sewage treatment process

With the improvement of water environment quality in China, the revised Integrated Wastewater Discharge Standard (GB8978- 1996) puts forward strict requirements on the nitrogen and phosphorus content of effluent, and the existing sewage treatment facilities focus on meeting the nitrogen and phosphorus discharge standards, so a variety of nitrogen and phosphorus removal processes have been developed [2]. The decentralized sewage treatment technology in villages and towns in China should meet the following requirements: the treatment effect of low-carbon nitrogen is better than that of pollutants, and the effluent nitrogen and phosphorus meet the standard; Low investment and energy consumption; Small floor space and integrated design; Less sludge discharge, simple operation and maintenance, and convenient operation and management.

1.2. 1A/O process

A/O (anoxic/aerobic) process is a widely used nitrogen removal process developed in the early 1980s. In anoxic denitrification, denitrifying bacteria use organic carbon in sewage as carbon source and nitrification reflux as electron acceptor to complete denitrification [3]. Main advantages: the alkalinity consumed by nitrification can be supplemented by the alkalinity produced by denitrification; The sequence of anoxic and aerobic tanks is beneficial to reduce the load of aerobic tanks and improve the removal rate of organic matter; Using raw sewage as carbon source reduces the construction and operation costs. Main disadvantages: because there is no independent sludge reflux system, the cultured sludge can not remove refractory substances; The larger internal circulation ratio increases the operating cost; The internal circulating liquid carries some dissolved oxygen, which destroys the strict anoxic environment and affects the nitrogen removal effect.

1.2.2A/A/O process

A/A/O (aerobic/anoxic/aerobic) process is developed on the basis of A/O process and has the function of simultaneous nitrogen and phosphorus removal. It can be used for secondary sewage treatment, tertiary sewage treatment and reclaimed water reuse, and has good nitrogen and phosphorus removal effect [4]. Effluent enters the secondary sedimentation tank for mud-water separation, supernatant and part of excess sludge are discharged, and part of sludge flows back to the anaerobic reactor. Sewage and phosphorus-containing reflux sludge enter the anaerobic zone, release phosphorus and generate energy under the action of phosphorus-solubilizing bacteria, and degrade some organic matter at the same time.

1.2.3 improve AAO process

In order to solve the contradiction between carbon source competition and simultaneous nitrogen and phosphorus removal in AAO process, researchers have made a lot of process improvements and developed the following processes: (1) UCT process to solve the problem of nitrate interfering with phosphorus release; In view of the shortage of carbon source, inverted AAO process and new simultaneous nitrification and denitrification nitrogen and phosphorus removal process, such as Dephanox[6], are proposed to change the water inlet mode. The UCT nitrogen and phosphorus removal process proposed by Uni-[7] (UNI-Uni-versityofCapeTown, South Africa) changes the sludge reflux from anaerobic zone to anoxic zone, and makes the sludge return to anaerobic zone after denitrification, thus reducing the influence of nitrate on phosphorus release in anaerobic zone. The anoxic tank of UCT process is divided into two parts, which receive the sludge returned from the secondary sedimentation tank and the nitration mixed liquor in aerobic zone, so that the denitrification of sludge and mixed liquor can be carried out separately, thus reducing the nitrate with insufficient denitrification from entering the anaerobic zone [8]. Advanced [9] Tongji University. In order to solve the contradiction of carbon source competition in AAO process, the anoxic zone is put at the front of the process and the anaerobic zone is put behind, and the inverted AAO process is developed, which puts forward a new carbon source distribution model for the conventional phosphorus and nitrogen removal process.

2 development of decentralized sewage treatment process in comprehensive villages and towns

The overall development trend of modern decentralized sewage treatment technology is integrated design, and a series of new integrated sewage treatment technologies have been well developed and applied. This technology greatly reduces the occupied area, changes the layout form of traditional technology in time and space, greatly simplifies the technological process of water treatment technology, and is suitable for treating urban sewage. According to space and time, this kind of process can be divided into two types [12]: one is to reasonably divide the internal space of the reactor, such as the integrated design of anaerobic zone, anoxic zone and aerobic zone in space. The other is an integrated oxidation ditch process that arranges the reaction, precipitation and other processes in time sequence. M.Ro[ 13], etc. Sewage passes through anaerobic zone, anoxic zone and aerobic zone in turn, achieving good integrated sewage treatment effect. The integrated OmbinedOxidationDitch developed by Pasveer[ 14] successfully integrated aeration, sedimentation, sludge separation and sludge reflux, and developed rapidly after development. UNITANK developed by Scotts Qingshui Company in Belgium is a patented technology, which does not need a secondary sedimentation tank. The sludge return system is simple and easy to realize automatic control. After completion and production, the effect is good [15].

The above are collected and sorted by Zhong Da Consulting Company.

For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd