SU994441A1 - Process for treating effluent precipitates - Google Patents

Abstract

The process is compression of the sludge, measurement of the pH thereof and reducing this value by sludge treatment with a coagulant, heating the sludge, treatment thereof with a flocculant, mechanical dewatering and subsequent neutralisation. The pH is reduced in this to the extent that it corresponds to the isoelectric sludge state and heating is carried out up to a temperature of 65 to 75 DEG C.

Description

(54) METHOD FOR TREATMENT OF WASTEWATER DRAINS

The invention relates to wastewater treatment, in particular to methods for treating sludge from household and progressed sewage, and may find application in treating sludge from pulp and paper mills, dairies, mills, cattle-breeding industrial complexes, and the like. when processing precipitation of municipal and domestic wastewater.

A known method of treating siege. wastewater, including compaction of primary sedimentation tanks and activated sludge, heating them with polyelectrolytes and mechanical dehydration of Cl.

With this method, an excessive amount of expensive polyelectrolyte is required, and, after mechanical dehydration, the precipitate has a relatively high moisture content.

The closest to-the pre-furnace to the technical essence and the achieved result is a method of treating sewage sludge, which involves consolidating the fermented sludge, heating it to 70-100 s by introducing low-pressure steam, cooling to 30-b C, lowering the pH

Bsad to 3-6 by adding metal salt and / or acidic agent, the subsequent neutralization of the precipitate, processing by polyelectrolytes and mechanical

5 dehydration NW 3.

This method provides for the preliminary digestion of sediment, which is conducted in meta-teens. The presence of methane in technology

The scheme of precipitation complicates and increases the cost of their treatment.

Heating the sediment to 70-10, by introducing low pressure steam and its subsequent cooling is the process

15 long-term and entails an increase in humidity and an increase in the amount of sediment as a result of steam condensation, which in turn increases the total & MaoiraH amount and equipment for its subsequent dewatering (centrifuges, filter presses, etc.); In addition, at this stage of processing, a part of the colloidal sediment substances goes into a dissolved state, therefore the liquid phase (centrate, filtrate), from disinfecting the precipitate, will be contaminated with dissolved organic matter. mineral and mineral inclusions, which entails a sharp increase in

30 COD and MIC and requires the processing of the liquid phase before it is discharged into the head wastewater treatment plants, the NTO also complicates the technology — and increases the cost of wastewater treatment and wastewater treatment. A decrease in the pH of the precipitate to 3–6 after preheating followed by neutralization (by increasing the pH) and the addition of polyelectrolytes after neutralization causes the treatment of precipitates to be introduced at varying pH. As a result, durable flakes cannot be formed. the basic requirement for dewatering sludge is violated, which reduces the efficiency of the equipment during the subsequent mechanical dewatering of the sludge, since the centrate or filtrate is contaminated with crushed flakes. In addition, the coagulation and flocculation of the precipitate is carried out at a temperature of 30-60 ° C and with a change in the pH of the medium, which does not ensure the irreversible coagulation of protein substances, i.e. part of the protein substances of the trans: edith back to the colloidal state and for their coagulation and flocculation additional amounts of acidic agents and polyelectrolytes are required. In turn, the coagulation and flocculation of the precipitate at sub-optimal pH values do not ensure the maximum possible removal of bound moisture from the precipitate, with the result that the concentration of dehydrated sediment will be relatively small. When fermenting the sediment, decomposition and acidification of organic nutrients occur, which reduces its fertilizing value. The aim of the invention is to simplify the process and increase the efficiency of the process. The goal is achieved by the fact that according to the method of treatment of sewage sludge, which includes compaction of sediments, heating them, reducing the pH of precipitation by adding a metal salt and / or an acidic agent, subsequent neutralization of precipitation, flocculation of them with polyelectrolytes and mechanical dehydration, after compaction of sediments reduce pH , heated, flocculated by polyelectrolytes, mechanically dehydrated, and then neutralized by precipitation, while lowering the pH to a value corresponding to the isoelectric state of the precipitates. heats up but the preferred choice for 0.2-3.0 min to BZ-UX C by immersion of the gas burner or the spiral heat exchanger. The treatment is carried out directly after the primary sedimentation tanks and activated sludge, i.e. the degree of fermentation of sediments is excluded, and, consequently, the use of methane-tenes, which simplifies and cheapens the treatment of sediments. A decrease in pH immediately after compaction by the addition of a metal salt and / or an acidic agent to the precipitate until the isoelectric state of the precipitate is obtained, i.e. until the state when its particles are electrically neutral, the subsequent short-term heating to 65-75 ° C for 0.2-3.0 minutes and flocculation of the precipitate in the heated state by polyelectrolytes contribute to the formation of large compact and durable flakes, i.e. fulfillment of the main requirement imposed on the conditioned sludge, which ensures an increase in the efficiency of subsequent sludge dewatering on the mechanical equipment, the achievement of the maximum concentration of dewatered sludge and its friable shape. When heated to b5-75 ° C for 0.2-3.0 minutes near the isoelectric point of the sediments, coagulation of sediment protein substances occurs irreversibly, preventing the process of dissolving colloids, resulting in an increase in the quality of the liquid phase after mechanical dewatering. The sludge is heated using an immersion gas burner or a spiral heat exchanger, which contributes (to the protection of the initial sludge concentration, i.e. after compaction, the sludge concentration does not decrease during its physicochemical treatment. However, when using immersion gas burners, carbon monoxide containing in combustion gases, it dissolves in the sediment, forming carbon dioxide and, thus, reduces the consumption of acidic agents for acidification, therefore, it is preferable to use submersible e gas burners. Subsequent neutralization of mechanically dehydrated sludge by treating it with unstained lime. Further increases sludge concentration due to partial evaporation of moisture, since this treatment generates a large amount of heat. In case of sludge dewatering in natural conditions (sludge plots) it is possible to neutralize before or after dehydration. Since the proposed method treats a crude sludge (unfermented) containing less colloidal substances and having more the low pH value, what is the value of the fermented sludge, then the amount of electrolytes ((metal salt, acidic agent) and polyelectrolytes for its processing also decreases, which allows

reduce the cost of processing precipitation.

In addition, nutrient organic substances are preserved in the sludge treated by the proposed method. which increases its fertilizing value.

The method is carried out as follows.

A precipitate from the primary clarifiers (concentration 0,) is mixed with active sludge (concentration 0.3-1, 0% J and jointly compacted in a gravity sealer with a stir bar. The pH of the compacted sludge is determined. Then the pH value is determined corresponds to the electrical state of the precipitate, and the necessary doses of the acidic agent (acid) and / or metal salt to lower the initial pH to a value corresponding to the electric state of the precipitate. The indicated doses of acid and / or metal salt are introduced into the precipitate. The pH of the precipitate corresponding to its isoelectric state is heated by means of an immersion gas burner or a spiral heat exchanger for about 2-3 tO min up to a temperature of 5–75 ° C. Polyelectrolytes are added to the heated K precipitate, after which it is dehydrated by a cent | rifugs or filter presses.

Quick lime (or alkali) is added to the dewatered sludge to neutralize it, as well as to further reduce the moisture content of the sludge.

For example, three equal portions of sludge are prepared, with each portion of the sludge from primary settlers with a concentration of 0.6% in an amount of 18 m / h and excess activated sludge with a concentration of 0.4% in an amount of 27 m / h. ratio by dry matter 1: 1) and compacted to a concentration of 4.5% in a gravity sealer, with a core stirrer.

After compaction, the initial pH of the precipitate is determined, which is 6.95. Then, using graphite from primary SINTERS:

18

amount, m / h

0.6

concentration,%

To determine the dependence of the time of capillary suction (UHF) on the pH value of the sediment, a value is determined that the pH corresponds to the isoelectric state of the precipitate, which is 3.0. VKV characterizes the method of sediment to give vvag.

With a slight deviation of pH from 3.0, the UHV of the precipitate increases, and, consequently, its ability to absorb moisture deteriorates.

Then, using the graph showing the dependence-reduction of the pH of the precipitate on the dose of sulfuric acid and ferric chloride, the salts of FeCt3r needed to reduce the pH from 6.95 to 3.0 doses of the acid, PEC, and the salt of Recez are determined. 6.7%, dose (H25C | f + GeSSz) 3.0 + 5.5% and dose of salt

0 FeCtj 10.0%.

These doses are introduced into the initial compacted sediment. When a pH of 3.0 is reached, each portion of the precipitate is heated with an immersion gas burner to 70 s for 1.5 minutes. Polyelectrolytes are added to the preheated sediment, with cationic flocculant in the amount of 0.150% of dry matter being added to the first batch.

sediment, in the second and third portions of 0.135% polyacrylamide. After that, the residue is mechanically dehydrated in a centrifuge.

The dewatered sediment has a humid degree of 70-72% and a friable structure. When centrifuging the sediment thus treated, the effect of retention of solid particles is 98-99%. The dehydrated sludge is mixed with 10% iEet (by dry matter) to become pH and this one is used

for the preparation of vegetable soil. Since for different types of sediments the pH value corresponding to their isoelectric state is

5 is not the same (for each aeration station its own pH value), then the graphs are also different. For each type of precipitation, their dependency plots should be constructed.

0 The test results of the proposed and known methods are given in table. one..

.Table 1

18

1.35

18

0.6

8.0

0.6

Excess active tint amount m / h

27

Compacted precipitation mixture: amount, m / h, concentration,%

Consumption of sulfuric acid,% Consumption of ferric chloride,%

Heat consumption for heated264i10 VA, kcal / h

0.150

Flocculant flow rate,%

Humidity dehydrated

72

draft,%

Retention effect

98-99 solids,%

g

COD fugata, g / l

ten

Lime consumption,% Loose, Cake structure is non-flowing. Table. Table 2 shows the data on the 50 effect of preheating time and temperature. Table 12. one (

27

27

5.4

264x10 264x10

0.135

0.135

0,200

71

70

77

98-99

94-95

9В-99

one

one

ten

ten

ten

Claims (2)

Table 2 Loose, net-Pastoobcha of different types on the quality of sludge treatment, UHV initial sludge (before heating) 76 s. As can be seen from the table. 2, the concentration is greatest for the precipitate heated to 0.2-3.0 minutes. The technical and economic effect of using the method is to simplify the treatment of precipitation, increase its efficiency, reduce the consumption of expensive polyelectrolytes, and improve the fertilizer sedimentation rate. In addition, as a result of the exclusion of the digestion stage, safety conditions will be improved. Claim 1. A method of treating sewage sludge, including compacting the sludge, heating it, reducing the pH of the sludge by adding a metal salt and / or an acidic agent, neutralizing, flocculation with polyelectrolytes and mechanical dehydration, so that in order to simplify the process and increase the efficiency of the process, after compaction of the precipitates, the pH shines, is heated, flocculates with polyelectrolytes, mechanically dehydrated and then neutralized, while lowering the pH to the value corresponding to isoelectric the general state of precipitation. 2. Method POP1, characterized in that the precipitates are heated for 0.2-3.0 minutes to 65-75 C. 3. The method according to Claims 1 and 2, which are separated by the fact that heating is carried out using submerged gas burner or heat exchanger. Sources of information taken into account in the examination 1. For the FRG I 2103970, cl. C 02 C 3/00, 1978. 2. For Germany FRI 2317673, cl. From 02 to 3/00, 1974.