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Abstract

Contents


Introduction

Sewage and wastewater treatment is one of the most important environmental problems in urban areas. As a result of the biological wastewater treatment by aerobic mechanism there is a large amount of waste   — sewage sludge (SL) consisting mainly of waste activated sludge. Despite the fact that the SL is classified as low hazard (IV class) and in the real world is placed openly on the sludge beds, the latter forms the main source of pollution of the three components of the natural environment: soil, air, surface and groundwater. For example, pollution and degradation of soils, determining the quality of drinking water, food, can be factors in the transmission of infectious agents [1].


1 Topic relevance

Relevance of the tipoc is in the fact that the re-use of sewage sludge will significantly reduce the area of the existing maps by utilizing sludge SL as organic fertilizer and as a result, will reduce the risk of environmental hazards.


2 Goal, objectives, object, subject of study, the planned scientific novelty

The main goal of the study is to investigate the feasibility of using sewage sludge to sludge fields as organic fertilizer using Makeyevka industrial management of water suppy and sewage utility Water of Donbass as an example.

To achieve this goal the following tasks should be solved:
1) an analysis of the technological wastewater treatment schemes and finding of the maximum stages of waste;
2) to explore the agrochemical, chemical and sanitary-bacteriological indicators of sewage sludge;
3) to examine the conditions of the possible use of sewage sludge as organic fertilizer for vegetable crops;
4) to develop evidence-based recommendations on the reuse of sewage sludge;
5) determine the ecological and economic benefits of using organic fertilizers to restore soil fertility in the region.

Research object: sewage sludge treatment plant of the city of Makeyevka.

Research subject: agrochemical, chemical and sanitary-bacteriological evaluation of sewage sludge as well as the options for their use as an organic fertilizer.

Planned scientific novelty: research results will show the use of sewage sludge as a fertilizer mixture with certain excipients.


3 Technological scheme of wastewater treatment

Treatment facilities are part of the Makeyevka industrial management of woter suppy and sewage utility Water of Donbass and represent a complex production facility.

According to the permit for special use [2] daily on urban wastewater treatment plant 80 thousand m³ household, industrial and storm sewage are processed. Schematic diagram of wastewater treatment is presented in figure 1.


Schematic diagram of the wastewater treatment

Legend: I — raw sewage sludge; II — excess activated sludge; III — return activated sludge; IV — waste activated sludge; V — water-sludge mixture; VI — dewatered sediment.

1 — lattice; 2 — sand trap; 3 — primary settling tanks; 4 — pumping station raw sewage sludge; 5 — aeration; 6 — secondary sedimentation tanks; 7 — pumping station activated sludge; 8 — aerobic stabilizer; 9 — sludge beds; 10 — sludge ponds; 11 — contact reservoir

Figure 1 — Schematic diagram of the wastewater treatment


In the first phase of purification (mechanical) grids and horizontal bunker sand traps are used to catch heavy solids. Next partially treated waste water flows into the primary radial sumps, where water remains stationary for several hours, while the two processes take place simultaneously:
1) sedimentation of the heaviest particles of organic matter (30–50 %) at the bottom;
2) surfacing of fatty and oily substances as well as petroleum products. The raw sewage sludge is sent to the aerobic stabilizer and popid material (silt–raw) collected in drums is sent to regeneration or combustion [3].

The clarified and partially treated wastewater flows from the primary clarifiers in biological treatment unit (BTU), where in aerotanks a part of the organic pollutants undergoes degradation as a result of contact of the purified waste water with activated sludge with simultaneous saturation of the air with oxygen.

The purified in aerotanks wastewater comes secondary settling tanks, where the sedimentation of the activated sludge takls place in the process of which its microorganisms its scaly surfaces adsorb suspension minute.

The process of BTU is accompanied by the formation of a large with their amount of sediment, which is a dying off or surplus active silt [3]. For the purpose of dewatering sludge from aerotanks and secondary clarifiers are handled in aerobic stabilizers. Then the dewatered sludge is fed to a specially prepared lands — sludge beds.

Next wastewater comes to contact tanks a for disinfection with sodium hypochlorite, as result achieving the degree of cleaning corresponds with the category of regulatory peeled and pipeline dumped into the river Gruzskaya [4].


Conclusions

Review of the literature and preliminary experimental analysis of sewage sludge leads to the conclusion about the possibility of their use as an organic fertilizer, on the condition of compliance with the sanitary standards on the content of heavy metals. In case of their absence in the composition of SL there will be developed and evidence-based guidelines for recycling, which will, reduce the damage currently natural environment components, including flora and fauna, as well as the population of the city of Makeyevka.

This master's work is not completed yet. The term of final completion: May 2017. The full text of the work and materials on the topic can be obtained from the author or his head after this date.


References

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