RU2158237C1 - Methods of biological treatment of sewage waters and treatment of sludges - Google Patents

Abstract

FIELD: treatment of sewage waters and their sludges with microorganisms; applicable in biological treatment of municipal and industrial sewage waters from organic impurities, nitrogen compounds and for stabilization of sludges. SUBSTANCE: flow of sewage waters is divided into two flows, one of which not exceeding in value of hourly average flow rate of sewage waters is directed to multistage aerobic bioreactor operating on community of freely floating and fixed microorganisms. During hours when sewage water flow rate exceeds hourly average one, its excessive part enters multistage aerobic mineralizer, and after sludge separation, sewage waters together with sludge water are supplied to aerobic bioreactor. Stabilized sludge from aerobic mineralizer is withdrawn for dewatering not earlier than in 6 h after stopping of supply of sewage waters. EFFECT: reduced volumes of aerobic bioreactors and air consumption for treatment of volume unit of nonuniformly supplied sewage waters, increased degree of decomposition of ashless matter of sludge. 3 cl, 5 dwg, 3 tbl, 1 ex

Description

 The invention relates to the treatment of wastewater and its precipitation of microorganisms and can be used in the biological treatment of urban and industrial wastewater from organic impurities, nitrogen compounds and to stabilize precipitation.

 There is a method of extended aeration of wastewater, which consists in continuous aeration of a mixture of wastewater and activated sludge recirculated from secondary sumps, in which wastewater treatment and stabilization of sludge are carried out at the same time [1].

 The disadvantages of this method are large volumes of structures, excessive air consumption for aeration, insufficient degree of decomposition of ashless sediment.

 There are also known methods of using activated sludge fixed on a fiber nozzle during aeration of wastewater and sediments in tanks of aerobic bioreactors filled with a fiber "ruff" nozzle, and allowing the biological treatment and stabilization of sediments to be carried out more intensively [2, 3].

 However, with uneven wastewater inflow, bioreactors provide purification with a maximum wastewater flow, and with a minimum flow, these structures are underloaded, although the degree of decomposition of ashless sediment is higher than during stabilization in structures without a nozzle, but still insufficient.

 The closest in technical essence is a method of wastewater treatment, including aeration of wastewater together with free-floating and attached activated sludge, recirculation from secondary sumps, mineralization of sediments with free-floating and attached sludge, separation of stabilized sludge from the stabilized sludge and its supply to aeration, and compacted sludge for dehydration [4].

 But to implement this method, large capacities of biological treatment facilities, a significant air consumption for aeration, and a low degree of decomposition of the ashless sediment matter during stabilization in aerobic mineralizers are required.

 The basis of the invention is the task of improving the method of biological wastewater treatment and sludge treatment, in which by dividing the wastewater flow rate into two, one of which, not exceeding the hourly average wastewater flow rate, is sent to the first stage of a multistage aerobic bioreactor, the remaining wastewater in hours, when its consumption exceeds the average hourly, it enters a multistage aerobic mineralizer equipped with a sludge separator, which ensures a uniform load of pollution on the biomass microorganisms of this stage during the day, regeneration water from the after-treatment stages, as well as water returned from the MAM sludge separators, contains a disparate amount of organic impurities, therefore, they do not affect the load on the biomass of microorganisms, thereby reducing the volume of aerobic bioreactors and consumption air to clean a unit volume of unevenly entering wastewater, the degree of decomposition of ashless sediment increases.

The problem is solved in that in the method of biological wastewater treatment and sludge treatment, including aeration of wastewater together with free-floating and attached sludge, aerobic mineralization of sludge with free-floating and attached activated sludge, as well as recycling of free-floating activated sludge, according to the invention, the following distinctive features are provided:
- wastewater flow rate not exceeding the hourly average is fed for aeration to the aerobic bioreactor;
- at hours when the wastewater flow rate exceeds the hourly average, its greater part is sent to an aerobic mineralizer,
- from the aerobic mineralizer, after sludge separation therein, the wastewater together with the sludge water is supplied to the aerobic bioreactor;
- the stabilized sludge from the aerobic mineralizer is removed for dehydration no earlier than 6 hours after the cessation of wastewater supply to it.

 In addition, wastewater and sludge are sent to at least a three-stage aerobic mineralizer dispersed, crude sludge is sent only to the first stage of the mineralizer, excess activated sludge is supplied in equal proportions to the first and second stages, and waste water to the second and third stages of the mineralizer in a ratio of 1: 2 - 1: 3, while a ratio of 1: 3 is used in the case of supplying to the first stage of the mineralizer of the raw sediment primary sedimentation tanks, and the total amount of ashless substance precipitation (excess active or raw of sludge) supplied to the aerobic mineralizer should be 2-3 times larger than the amount of dissolved organic substances entering it from the wastewater.

 Analysis of known technologies related to biological wastewater treatment and sludge treatment showed that no technical solutions containing the same set of essential features as the claimed method were found, which allows us to conclude that the claimed method meets the criterion of "novelty "

 An analysis of the essential features that are distinctive from prototypes showed that such or similar features in known technical solutions, with the manifestation of the same properties that they exhibit in the claimed combination, were not found, which allows us to conclude that the claimed method meets the criterion " significant differences. "

 Separation of the wastewater stream into two, one of which, not exceeding the hourly average flow rate of wastewater, is sent to a multistage aerobic bioreactor, and at hours when the wastewater flow rate exceeds the average hourly flow, its greater part is fed to the aerobic mineralizer, from which after sludge discharge therein water along with sludge is fed into the aerobic bioreactor, which allows to obtain a new higher result, expressed in a uniform load of pollution on the biomass of microorganisms during the day, in addition, water, returning When removed from the mineralizer, it contains an incomparably small amount of organic impurities; therefore, they do not affect the load on the biomass of microorganisms, which allows one to reduce the volumes of aerobic bioreactors and increase the degree of decomposition of the ashless sediment matter.

 The proposed method is illustrated in the drawing, where figure 1 shows the technological scheme of biological wastewater treatment and sludge treatment.

 The method of biological wastewater treatment and sludge treatment is as follows.

Sewage flow rate Q _calc share in the distribution chamber 1 into two streams, one of which, the magnitude does not exceed a weight hourly flow rate Q _cf. ^h is fed through primary sedimentation tanks 7 in multistage aerobic bioreactor (MAB) 2, and the second, equal in magnitude to the difference between _rasch Q and Q _cf. ^hours and certainly not continuously supplied to the multistage aerobic mineralizer (MAM) 2 in MAB is first treated sewage and free-community of microorganisms attached to the first stage 2a MAB 2, the first sludge mixture mortars neither 2A MAB 2 flows into the sludge separator 2b of the first stage of MAB 2, from where waste water is sent by stream II to the second stage 2c of MAB 2, return activated sludge by stream III is pumped to the entrance to the first stage 2a of MAB 2, and excess activated sludge by stream IV is discharged into the first from the second stage of MAM 3, to the first stage of MAM 3, the raw sediment of primary settlers 7 is discharged by stream VII, MAM 3 also has a sludge separator 4, in which the effluents of stream Ib are separated from the stabilized sludge and enter the entrance to the first stage 2a of MAB 2 saturated with nitrites and nitrates and freed from most of the organic compounds that pollute them, from the MAM sludge separator 4, the stabilized sludge is sent to the dewatering device 5, from where the solid phase is discharged by stream V for disposal as fertilizer, and the sludge water, together with wastewater stream II, enters to the second stage 2B of MAB 2, from where the sludge mixture flows into the sludge separator 2g of the second stage 2b of MAB 2, from which the return sludge is pumped to the head of the second stage 2b of MAB 2, and the excess activated sludge together with the excess sludge of the first Stage 2a of MAB 2 is discharged into MAM 3, the wastewater after the sludge separator 2g goes further to the aftertreatment stage 2d and into the decontamination facilities 6, the treated wastewater by stream VI can be directed to the technical needs of industrial enterprises. At all stages of MAB 2 and MAM 3 and aftertreatment, compressed air is provided.

 In the first stage of MAM, where the flow of wastewater does not flow at all, the processes of oxidation of organic substances that make up the suspension, as well as adsorbed on suspended particles, proceed. Under the influence of free-floating and attached microorganisms, simultaneously with the processes of exogenous and endogenous oxidation of the substrate, ammonification, nitri- and denitrification also occur.

 The supply of the total volume of crude sludge of the primary settlers and half of the total volume of excess activated sludge from the MAB sludge separators of the first and second stages to the first MAM stage provides the fastest possible processing of the organic matter contained in the raw sludge due to the constructive and energy exchange in the cells of aerobic microorganisms that came with excess activated sludge from the MAB. After the first stage of MAM, the precipitation mixture is a homogeneous mass consisting only of activated sludge and sludge water. It is advisable to equip the first stage of MAM with its sludge separator in order to remove the waste products of microorganisms working with high concentrations of biomass of microorganisms and substrate with silt water.

 The total concentration of organic substances in this sludge water is at the level of the amount of pollution in the wastewater after secondary settling tanks of aeration tanks with free-floating activated sludge, but in this sludge water the concentration of nitrogen compounds (both ammonium and nitrite and nitrate) is higher. Compounds of oxidized forms of nitrogen create a reserve of aerobicity of the medium not only in the volume of water in the MAB first stage structure, but also inside the nozzle, where air access is difficult. In the zone of microorganism fixation through the use of nitrite and nitrate oxygen, denitrification processes take place, which are also accompanied by the oxidation of organic wastewater contaminants, especially easily oxidized ones, contributing to the fast binding of oxygen dissolved in water.

 In the second stage of MAM, the mineralization of activated sludge begins directly. In the process of lysis of the cell membrane of dying microorganisms, an intracellular substance is released, during the oxidation of which (and it consists of amino acids) nitrites and nitrates are formed. The MAM nozzle holds microorganisms - denitrifiers - and due to their vital activity the process of aerobic mineralization does not come to a standstill. The fact is that, if only nitrification processes occur as a result of the oxidation of amino acids, the sludge mixture will be acidified, and nitrites and nitrates as waste products inhibit the continuation of oxidative processes. It has been experimentally established that denitrification is accelerated by the addition of easily digestible organics. At the same time, the addition of easily digestible organics should not be constant and there should be a limited amount, since otherwise the biocenosis of aerobic mineralizers will not be oriented to aerobic mineralization of activated sludge biomass. For example, if glucose is periodically added in certain doses to a stabilized precipitate with a decay of an ashless substance of 45%, then with a certain increase in the load of organic substances on the biocenosis of microorganisms - stabilizers, the decomposition of an ash-free substance of a stabilized precipitate increases and reaches a glucose application rate under a certain regimen 58% without increasing stabilization time.

 In FIG. Figure 2 shows the effect of the ratio (K) of the amount of ashless sludge substance supplied for stabilization (a) to the amount of glucose introduced (m) on the degree of decomposition of the ashless sludge substance during stabilization.

 As can be seen from FIG. 2, when K is equal to 2–3, a sharp increase in the degree of decomposition of the ashless sludge material upon stabilization is observed. However, such a jump in the degree of decomposition is possible with a certain mode of glucose supply. With a total stabilization time of 3 days, glucose administration should be carried out in three doses with a duration of glucose administration in one dose of 12-18 hours (Fig. 3) and a break between doses of 6-12 hours. Deviation of the duration of administration in either direction leads to a decrease in the degree decay. Moreover, the deeper it is desirable to obtain the decomposition of ashless sediment, the greater the dose of easily digestible organics should be introduced into the stabilization process.

 This phenomenon was laid in the basis of the invention. That is, not only the task was to reduce the size of the aerobic bioreactor and to reduce the air consumption for the wastewater treatment process, but also to rationally use the wastewater as a source of easily digestible organic matter to increase the degree of decomposition of ashless substances produced at the sewage treatment plant.

 Since urban wastewaters differ in composition, the number of pollutants contained in them required determining the boundaries of the loads on the biocenosis of aerobic mineralizers by the amount of easily digestible organic matter added to the wastewater compared to the dry ashless substance of the stabilized sludge and the regimen of applying this easily digestible organic.

 Example 1 shows the effect of the amount and mode of application of easily digestible organics on the degree of decomposition of the ashless substance of excess activated sludge from aeration tanks.

 Example 1. Activated sludge was loaded into an aerobic stabilizer model with an initial concentration of 5-8 g / l using an ashless substance. The total stabilization duration was 3 days. The glucose solution was dosed into a stabilizer in three divided doses. The duration of each dose was 16 hours, the interval between injections of a glucose solution was 8 hours. After stabilization (after three days), the content of stabilized ash-free substance was determined or its decomposition was evaluated. For comparison, an experiment was carried out without adding glucose (experiment 1) table. 1.

The data table. 1 indicate an increase in the degree of decomposition of the ashless sludge material during stabilization with the introduction of easily digestible organics in the indicated mode, and the highest degree of decomposition corresponds to the ratio of the ashless sludge substance to the total amount of added glucose (based on BOD, _full , equal to 2 - 3.

 At the same time, with a constant supply of glucose solution to the stabilizer during the entire stabilization period, the degree of decomposition of the ashless sludge substance is only 43-45%, which is caused by a change in the biocenosis of denitrifying microorganisms with a reorientation of them to the consumption of easily digestible organics (Table 2).

Let us compare the obtained data with the data on wastewater equal to the volume α Q _days when MAM is supplied to MAM, where α is a coefficient that takes into account the share of daily consumption entering MAM. Then the increase in excess activated sludge in all bioreactors will be
Pr = 0.8 C + 0.3 L _en ,
where C is the initial concentration of suspended solids in the wastewater entering biological treatment;
L _en - BOD is _{full of} wastewater after initial sedimentation.

The total amount of excess sludge and wet sludge on dry matter, formed during cleaning and sent to MAM
G _total = [Pr + (C _en - C)] Q _day (1- α)
or ashless substance
G _be = 0.7 G _total

The amount of organic matter in accordance with the BOD is _fully supplied to MAM with waste water consumption
G _BOD = α Q _day L ' _en ,
where L ' _en - BOD of unclarified wastewater.

Режим поступления в МАМ сточных вод, например, при коэффициенте неравномерности 1,6 приведен в табл. 3.The ratio of the ashless substance mixture flowing to the amount of precipitation of organics _BOD will be

The mode of wastewater entering MAM, for example, with a non-uniformity coefficient of 1.6, is given in table. 3.

Как видно из приведенных данных, величина K, полученная при поступлении в МАМ сточных вод, соответствует значениям K (табл.1), при которых степень распада беззольного вещества ила максимальна. Кроме того, соответствуют друг другу и режимы поступления в стабилизируемый ил органических веществ со сточными водами и при введении раствора глюкозы.Thus, for wastewater flow rate with a total coefficient of unevenness of 1.6 α = 0.203
Taking into account that with a specific average daily water discharge of 200 l / (day. People): C _en = 325 mg / l; C = 150 mg / L; L ' _en = 375 mg / l; L _en = 0.85 L ' _en = 319 mg / l, then we get

As can be seen from the data presented, the value of K obtained upon entering sewage into MAM corresponds to the values of K (Table 1) at which the degree of decomposition of the ashless sludge material is maximum. In addition, correspond to each other and the modes of entry into a stabilized sludge of organic substances with wastewater and with the introduction of a glucose solution.

 A similar analysis for wastewater flow with a coefficient of total unevenness of 1.8 and 1.4 show that the K value is 2.18 and 3.12, respectively.

 An increase in the degree of decomposition of ashless matter or during its stabilization in MAM is associated with the denitrification process, in which the oxygen consumption of nitrites, nitrates and organic matter occurs. Without the addition of organic substances, the rate of denitrification, as well as the amount of sludge organics consumed for denitrification at the beginning of stabilization, is maximum and minimum towards the end of stabilization. This is due to the fact that in the initial period of stabilization, the ratio of easily digestible and digestible organics is maximum and minimum towards the end of stabilization. In this case, there is also some accumulation of nitrates in the silt water.

 The supply of wastewater containing easily digestible organic matter to the second and third stages of MAM in a ratio of 1: 2 (i.e., to the second stage to 1 part, and to the third stage to 2 parts of wastewater) equalizes the denitrification rate, increases the overall decay of ashless sludge, and reduces the total oxygen consumption due to more complete use of nitrates.

 The indicated proportion of the introduction of wastewater into MAM can be confirmed by the following considerations.

 If the total amount of ashless sludge material supplied for stabilization is taken as a unit, then for 1.5 days of stabilization due to decay, 0.55 of its initial amount will remain, and for 3 days - 0.42. Of this amount, 0.26 falls on the digestible organics (figure 4).

 The required amount of easily digestible organics added to MAM, for example, at K = 2.5, should be in units of 0.4.

где α - часть органического вещества, вводимого во вторую ступень МАМ.Then, to ensure the same ratio of easily digestible to hard to digest organics in the second and third stage, the ratio

where α is part of the organic matter introduced into the second stage of MAM.

 From this ratio α = 0.33, that is, 0.33 of the total amount of easily digestible organic matter should be fed into the second stage, 1-0.33 = 0.67 into the third stage, which corresponds to a ratio of 1: 2.

 Failure to comply with the above proportions leads to a decrease in the degree of decomposition of the ashless sludge substance (Fig. 5), where n is the ratio of easily digestible organics introduced into the third stage to those introduced into the second stage.

 When raw sludge is fed into the first MAM stage (according to the technology, sludge is unloaded from the primary settling tanks periodically), the load on activated sludge entering this stage in an amount of 50% of its total discharge increases. However, the sludge water separated after the first stage of MAM will not change its quality, since the organic matter of the raw sediment during its stay in this stage manages to oxidize partly, partly accumulate as reserve substances in the sludge cells and partially adsorb on the surface of the sludge flakes. The activated sludge entering the second stage of MAM, in this case, contains an increased amount of easily digestible organic matter in the form of adsorbed and reserve substances, which necessitates a decrease in the fraction of easily digestible organic matter supplied to the second stage and will change the proportion of adding it to the second and third stages to 1: 3.

 The supply of an hourly average flow of contaminated wastewater to the first stage of the MAB provides a uniform load of pollution on the biomass of microorganisms during the day. Regenerative water from the aftertreatment stages, as well as the liquid returned from the MAM sludge separator, contains an incomparably small amount of organic impurities, therefore they do not affect the load on the biomass of microorganisms of the first MAB stage.

 Therefore, the proposed method of biological wastewater treatment and treatment of sludge can reduce the size of the primary settlers and the first stage of the MAB by an amount equal to the unevenness of the flow of wastewater to the treatment plant, that is, almost no less than 1.5 times, without building additional volumes of capacitive structures, for example, flow averagers, in addition, the need for air at this stage of the MAB is reduced by 1.5 times, and the decay rate of the ashless sediment substance also increases.

Sources of information
1. SNiP 2.04.03-85 Sewerage. External networks and structures - M., Stroyizdat, 198b - p. 39.

 2. Gvozdyak P.I. Microbiology and biotechnology of water purification. - Kiev, Chemistry and water technology. T.p. N 9, 1989 - p. 854.

 3. Chernysheva E.N., Zavsigalova L.V. Experimental studies of aerobic stabilization of activated sludge in a structure with a fibrous nozzle. Sat scientific tr New technological processes and equipment in the field of water purification and pipelines. - Kiev, 1991 - p. eleven.

 4. Engineering equipment of buildings and structures: Encyclopedia / ed. S.V. Yakovleva - M .: Stroyizdat, 1994 .-- 512 p. (Prototype).

Claims (3)

 1. A method of biological wastewater treatment and sludge treatment, including aeration of wastewater together with free-floating and attached activated sludge, aerobic mineralization of sludge with free-floating and attached activated sludge, recirculation of free-floating activated sludge, characterized in that the wastewater flow rate not exceeding the hourly average is supplied for aeration into an aerobic bioreactor, and at hours when the wastewater flow rate exceeds the hourly average, the greater part is sent to an aerobic mineralizer, from where after sludge separation Wastewater together with sludge water is fed into the aerobic bioreactor, while the stabilized sludge from the aerobic mineralizer is removed for dehydration no earlier than 6 hours after the cessation of wastewater supply to it.  2. The method according to claim 1, characterized in that the sludge and wastewater are directed to at least a three-stage aerobic mineralizer dispersed, the raw sludge is sent only to the first stage of the mineralizer, excess activated sludge is sent in equal proportions to the first and second stages, and waste water - in the second and third stages of the mineralizer in a ratio of 1: 2 - 1: 3.  3. The method according to claim 1, characterized in that the total amount of dry ashless sediment - excess activated sludge and wet sludge supplied to the aerobic mineralizer should be 2-3 times greater than the amount of dissolved organic substances entering it from sewage.

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