SU887477A1 - Method of waste water purification - Google Patents

Description

Sewage water after gratings and sand traps is treated with reagents. Then the mixture of wastewater and reagents is settled in the sump for 1-1.5 hours. The settled water is filtered through a sand-gravel filter, then sent to aerated biological ponds with alternating aerobic-anaerobic conditions and a total residence time of 3-5 days. The duration of the stay of water in each step of the biopond is 1-1.5 days. Aeration of water in the first stage of biopruda is carried out with an air flow rate that provides a dissolved oxygen content of 3-5 mg / l. The aeration of waste water in the subsequent steps of the biopruda is carried out with an air flow rate that provides alternation of zones with elevated (3-5 mg / l) and low (~ 0.5 mg / l) oxygen content. Aeration in the zone of release of purified water from biopruda is carried out with an air flow rate providing the content of dissolved oxygen of 5-7 mg / l.

The alternation of zones with high and low oxygen content contributes to the oxidation of residual organic pollutants in the process of the vital activity of saprophytic microorganisms, as well as to the course of nitrification-denitrification processes. When nitrification in the presence of oxygen dissolved in water, oxidation of ammonium nitrogen occurs by bacteria and nitrifying nitrites and nitrates. During denitrification, bacterienitrifiers in the absence of dissolved oxygen reduce nitrites and nitrates to free nitrogen with simultaneous oxidation of residual organic pollutants, which are a source of carbon to COj and water.

The total stay of wastewater in a biopond should be 3-5 days. A residence time of less than 3 days is not sufficient for organic oxidation, nitrification and denitrification. At the same time, the degree of purification decreases sharply. A stay of more than 5 days is impractical for economic reasons.

Example 1. Municipal wastewater with BPKb - 350 mg / l, COD - 728 mg / l, containing surfactant - 10 mg / l, total phosphorus - 15 mg / l, total nitrogen - 93 mg / l, treated with ferric chloride (100 mg / l in Fe2Oz) and polyacrylamide (1.5 mg / l), set aside for 1.5 hours, filtered through a sand-gravel filter at a speed of 7 m / h, sent to the aerated common biopond with a residence time in it waste water for 4.5 days. The duration of stay of water in each step is 1.5 days. Aeration in the first stage of biopruda is carried out with an air flow rate of 5, providing a content of dissolved oxygen of 3-5 mg / l. Aeration in the second and third stages of biopruda is carried out with an air flow rate of 3, providing alternation of zones with elevated (3-5 mgl) and low (~ 0.5 mg / l) dissolved oxygen content. The aeration of the purified water in the zone of release from the bioprud

air flow 5, providing the content of dissolved oxygen in water 5-7 mg / l.

Purified water has an average BOD5 - 7 mg / l, COD - 10 mg / l, surfactant -

0.9 mg / l, total phosphorus 0.8 mg / l, total nitrogen 10 mg / l.

Example 2. Municipal wastewater having a BOD-200 mg / l, COD-300 mg / l,

containing surfactant - 5 mg / l, total phosphorus - 12 mg / l, total nitrogen - 80 mg / l, oil products - 20 mg / l, treated with iron sulphate (60 mg / l in FeSO4) and poly.acrylamide (1, 0 mg / l), defended for 1 h, filtered through a gravel-sand load at a speed of 8 m / h and sent to the aerated bio-pond with a total residence time of 3 days in it. The duration of stay in each step of biopruda is 1 day. Aeration in the first stage of biopruda is carried out with an air flow rate of 4, which allows maintaining the concentration of dissolved oxygen in water at the level of

3-5 mg / l. Aeration in the second and third stages of biopruda is carried out with an air flow rate of 3, providing alternation of zones with an increased (mg / l) and low (O-0.5 mg / l) content of dissolved oxygen. The aeration of purified water in the zone of release from biopruda is carried out with an air flow rate of 4, providing a content of dissolved oxygen of 5-7 mg / l. Purified water had in

average BODK - 3.0 mg / l, COD - 50 mg / l, surfactant - 0.1 mg / l, total phosphorus - 0.4 mg / l, total nitrogen - 5 mg / l, oil products - 0.5 mg / l.

The table shows the comparative

data obtained during the treatment of waste water by the known and proposed methods.

The proposed method provides a higher degree of purification from organic pollutants and nitrogen compounds while reducing capital costs.

Saving capital costs when using aerated biological ponds instead of filters with porous loading will be 40-50% due to reduction of equipment costs 4 times and construction costs 1.6 times. Calculations relate to a station with a capacity of 25 thousand meters % ut

Claims (3)

1. A method of treating wastewater containing mineral and organic pollutants, including treatment with reagents, settling, filtering through a sand-gravel filter, characterized in that, in order to increase the degree of purification and the possibility of purification from nitrogen compounds, the waste water after filtration is processed in aerated biological ponds with alternating aerobic-anaerobic conditions. 2. A method according to claim 1, characterized in that the wastewater is treated in aerated biological ponds for 2-5 days. 3. The method according to claim 1, characterized in that the duration of the stay of waste water in each step of the biological pond is 1-1.5 days. Sources of information taken into account in the examination: . 1. US patent No. 3481868, CL. 210-19, 1969. 2. The patent of Switzerland No. 535184, cl. From 02 To 1/00, 1973. 3. USSR author's certificate number 590205, cl. C 02 C 5/00, 1978.