SU981249A1 - Process for purifying effluents - Google Patents

Description

(5) METHOD FOR CLEANING WASTE WATER

The invention relates to the biological treatment of wastewater and can be used, in particular, in urban sewers with the joint treatment of domestic and industrial wastewater. There is a method in which wastewater, after settling in the primary clarifier, is aerated with active sludge in aerotanks, the sludge mixture is sent for separation into a secondary clarifier, and part of the sludge is recycled from the secondary clarifier to the aerotank, and some as excess output from the aeration system f 1 j. However, when the hydraulic load on the aeration tank fluctuates and the load of contaminating impurities on the active sludge, such a method is used, this has been significantly difficult due to the swelling and increased wear of sludge from the secondary settling tank, resulting in a direct deterioration in the quality of treated wastewater. due to the presence of organic suspensions in them and a decrease in the cleaning efficiency due to a decrease in the mass of sludge in the aeration system. The closest to the proposed technical essence and the achieved result is a method that includes settling in the primary settling tank, aeration with activated sludge in the aero-tank, and in the sludge mixture before the separation in the secondary settling tank, a flocculating additive, in particular polyacrylamide at a dose of 5 mg / l, is introduced into the sludge mixture . Due to the introduction of a flocculating additive, the sedimentation properties of the swelling sludge are improved and the suspended matter content in the treated wastewater decreases. However, with the use of expensive synthetic flocculants, the cost of wastewater treatment increases. 398 The purpose of the invention is to simplify the process and reduce its cost. The goal is achieved by the fact that according to the sewage treatment method, including settling in the primary clarifier, aeration with active sludge in the aeration tank, separation of the silt mixture in the secondary clarifier, with the preliminary introduction of a flocculant additive, the sediment from the primary clarifier is introduced as a flocculating additive . Improving the sedimentation characteristics of activated sludge with the introduction of organic flocculants provides only with an increase in the size of sludge flakes. In addition to this effect, with the introduction of activated sludge in accordance with the proposed method, there is an increase in the amount of flakes due to a higher specific gravity of the sludge from the primary sedimentation tank compared to active sludge. In addition, if the organic flocculant is biologically inert, the pro-aerated sediment has a certain biological activity. The drawing shows the facilities and communications used in the implementation of the proposed method. The scheme includes a primary clarifier 1, an aero tank 2 with a regenerator 3 or without it, a secondary clarifier, an aeration tank 5 of the type of aerotank. Pipelines 6 are designed for sewage into the primary settling tank 1, pipeline 7 for feeding sewage into aeration tank 2, pipeline 8 for feeding circulating activated sludge from the regenerator 3 to the aeration tank, pipeline 9 for diverting the sludge mixture from aerotank 2, pipeline 10 - to feed sludge from the primary clarifier 1 to the tank 5; pipe 11 - to drain the activated sludge from the tank 5; pipeline 12 - to feed the sludge mixture with the activated sediment into the secondary clarifier 4; pipeline 13 to divert and the effluent from the secondary clarifier 4, line 1 - to supply the excess biomass from the secondary clarifier 4, any of the known constructions on compaction and dehydration of the solid phase, removable from the aeration system. 9 Sewage water through conduit 6 is fed to primary clarifier 1, from which settling wastewater via conduit 7 enters aerotank 2. where they are aerated with circulating activated sludge fed from regenerator 3 via conduit 8 or, during operation of aerotank without separate regeneration of sludge , directly from the secondary clarifier (not shown). The precipitate from the primary settling tank 1 is fed via conduit 10 to tank 5, where it is aerated for a period of time, after which the concentration of contaminating impurities is VPK in the supernatant separated at. not exceeding the target for wastewater after complete biological treatment. In the presence of coarse impurities in the sediment, it is advisable to remove them by passing the precipitate before feeding into the container 5 through a filtering device, for example, through a vibrating screen. The sediment from tank 5, activated by aeration, is introduced through conduit 11 into the sludge mixture, which is then sent via conduit 12 to the secondary clarifier k. The treated wastewater is discharged from the secondary settling tank through conduit 13, and the excess biomass is removed via conduit 15 and treated by any known method. In particular, this biomass can be compacted in a structure of the type of sludge compactor and delivered to the sludge beds for drying. Example. In one section of the aeration tank, sewage purification structures carry out cleaning with active sludge from a mixture of household and industrial (up to 30 of total consumption) wastewater, including the engineering and food industries, in the primary settling tanks. The total wastewater flow of 20000 m per day. during the entire period of operation of the facilities, the aeration system - secondary settling tanks works in an unstable mode with periodic increased removal of sludge (up to 40 mg / l) from secondary settling tanks and deterioration of treated wastewater by VPK to 25 mg, due to the swelling of sludge due to abundant development of filamentous bacteria . The value of the sludge index is 700-1200 cm / g. Because of such a high index, the maximum sludge concentration in the aero tank does not exceed 0.5 g / l, in the regenerator it is 1, 0 g / l. The second section of the aerotank is supplied with sediment of primary sedimentation tanks in the amount of 100-150 per day, to improve the conditions of aeration, diluted 6–7 times previously with untreated sewage, and aerated with supernatant 7-10 mg for the duration of aeration. The sediment activated in this way is introduced into the sludge mixture discharged from the first section of the aeration tank to the secondary section from the steadfast.

The results of the experiment are as follows:

Sludge concentration

g / l:

in the aeration tank 2.0-2.5

in the regenerator 3,8-, 0

Silt index

CMVr180-250

Concentration in purified

sewage:

suspended solids

mg / l 10 and less

Contaminants

00 BflKt, mg Ol / l 10 or less

As follows from the above data, the use of the proposed method ensures the safe use of scarce and expensive flocculants for stable operation of the treatment facilities.

with high quality of treated wastewater,

In the proposed method, the task of treating the sewage solid during the purification of the solid phase is partially solved, since its specific resistance to filtration is significantly reduced when aerating the sludge.

The proposed method eliminates the need to place on the site municipal wastewater treatment facilities of a bulky and complicated reagent plant unusual for the latter.

Claims (2)

1. Yakovlev S.V. and etc. Sewage. M., stroiizdat, 1976, p. 35b. 2.Water and Sewage works. 1977 reference number PP R11-R12.