RU2424199C1 - Method for biological treatment of waste water using active sludge - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to biological treatment of waste water. The method for biological treatment of waste water with active sludge involves putting sludge suspension into anoxide, aerobic and anaerobic zones of the volume of the treated water in an aerotank. Further, the sludge suspension passes into a secondary settling tank where it is separated into purified water and thick active sludge. The anaerobic zone of the aerotank is merged with the residue fermentation process - obtaining volatile fatty acids, in which a portion of flocculi of active sludge drops to the bottom, thickens to concentration of about 40 g/l in several days and after the fermentation process, the residue is carried by the flow of liquid from the anaerobic zone.

EFFECT: deep removal of organic substances and biogenic elements - phosphorus and nitrogen from waste water.

Description

The invention relates to the biological treatment of wastewater.

A known method of biological wastewater treatment (1), which includes mechanical wastewater treatment in the primary sump, after which the wastewater is fed into a bioactivator with microflora, which maintains the presence of zones with a heterogeneous oxygen content by means of controlled oxygen input, and then a mixture of wastewater water with activated sludge enters the secondary sump for separation into treated wastewater and activated sludge, which is constantly returned to the beginning of the bioactivator. The crude sludge after the primary sump is recycled to the input of the primary sump to create the conditions for the hydrolysis process and the heteroacetogenic process directly in the primary sump. In the secondary sump, zones with a heterogeneous oxygen content are created by adjusting the rate of recirculation of activated sludge from the secondary sump to the input of the bioactivator. Zones with heterogeneous oxygen content in the bioactivator are distributed in the horizontal direction. However, with this method, phosphate-accumulating bacteria do not have the ability to be under anaerobic conditions for a long time, which does not allow the process of auto-selection of phosphate-accumulating bacteria to be carried out quite efficiently and the sediment fermentation process to be carried out effectively in the anaerobic zone of the aeration tank.

The objective of the invention is the deep removal from wastewater of organic substances and nutrients - phosphorus and nitrogen.

The problem is solved by the method of biological treatment of wastewater with activated sludge, which includes the sludge suspension in the anoxic, aerobic and anaerobic zones of the volume of treated water in the aeration tank, the subsequent passage of the sludge into the secondary sump, where it is separated into purified water and condensed activated sludge, characterized in that that the anaerobic zone of the aeration tank is combined with the process of sludge fermentation (production of volatile fatty acids), in which part of the activated sludge flakes sink to the bottom, compacts to a concentration about 40 g / l for several days and after the fermentation process, the sediment is carried out by the fluid from the anaerobic zone.

As a result of the absence of forced sludge in this combined zone, this zone can be called the "ripening" zone.

The oxygen content in the compacted sediment drops to values of 0.2-0.1 mg / L, nitrates to values less than 1 mg / L. At the same time, phosphorus accumulating bacteria use the polyphosphates accumulated in the cell and the phosphorus content in the culture fluid increases by tens and hundreds of times (from tenths of mg / l to 50-150 mg / l).

At the same time, hydrolysis and fermentation of organic matter of activated sludge (sediment) to volatile fatty acids occurs and their content in the culture fluid increases from 0.3-0.7 to 4-6 mg.eq / l (in terms of acetic acid).

When the sludge (sediment) is at the bottom of the "ripening" zone for several days, the gas released during the fermentation process raises the compacted sludge to the surface and it is carried out by the fluid flow from the "ripening" zone.

This process - the subsidence of part of the incoming sludge to the bottom and the ascent of the fermented is continuous. To prevent methane fermentation, short-term air supply to the ripening zone is possible through aerators installed at the bottom of the zone.

The advantages of the method are: a significantly longer (tenfold) stay of sludge containing phosphate accumulating bacteria in the anaerobic zone of "ripening" compared to the residence time of the liquid, which allows for relatively small volumes of the anaerobic zone to achieve a long residence of phosphate accumulating bacteria under anaerobic conditions, the possibility carry out deep hydrolysis and fermentation of the sediment directly in the anaerobic zone - the zone of phosphate-accumulating bacteria, while mainly Abzhaya this particular group of bacteria with fatty acids.

At the same time, there are no expenses for pumps and electricity for organizing anaerobic circulation of silt slurry.

The application of the method made it possible, due to the partial sedimentation of sludge flakes in the "ripening" anaerobic zone, to maintain a wider spectrum of sludge composition and age in the aeration tank, which allows better combining of nitro-denitrification and dephosphotation processes, as well as the ability to promptly stop the fermentation process from switching to the methane digestion mode by supplying air to the ripening zone through aerators installed at the bottom of the zone.

References

1. RF patent No. 2296110, 2005

Claims (1)

The method of biological treatment of wastewater with activated sludge, comprising finding the sludge suspension in the anoxic, aerobic and anaerobic zones of the volume of water to be treated in the aeration tank, the subsequent passage of the sludge suspension into the secondary sump, where it is separated into purified water and condensed activated sludge, characterized in that the anaerobic zone the aeration tank is combined with the process of sludge fermentation - production of volatile fatty acids, in which part of the activated sludge flakes sink to the bottom, compacts to a concentration of about 40 g / l for several days and after the fermentation process, the sediment is carried out by the flow of fluid from the anaerobic zone.