FI121506B - Biological purification procedure - Google Patents

Description

Method for biological purification

The present invention relates to a process for biological purification based on the purification of a process liquid, such as waste water, at least in part by a batch active sludge process wherein aeration of the process liquid, separation of the pure liquid and removal of the purified liquid take place sequentially. The liquid to be treated is fed to a process space containing activated sludge, wherein the activated sludge is aerated, at least below, by aeration air supplied through an air distribution arrangement substantially connected to the bottom of the process space through a flow arrangement to oxidize the microorganisms in the The above 20 methods have been applied, for example, to Ekora Engineering Office

Oy developed and marketed by HKN wastewater treatment plant.

For example, wastewater is purified mechanically, chemically, biologically or in combination depending on the quality of the wastewater. Various film techniques are also used. Exceptionally difficult wastewater can also be treated by evaporation. Generally, however, most treatment plant demand is directed to the treatment of residential water. These wastewaters are of biological origin, so it is also advantageous to purify them biologically. The same principle is used to treat wastewater from the food industry as well as from the forest industry.

At present, the majority of biological treatment plants operate in the so-called. the activated sludge method, which in simplified terms means aeration of the waste water, ie the supply of oxygen to microorganisms, which in turn use waste water contaminants (nutrients). Technically, a sludge treatment plant can be technically implemented in two ways, for example.

5

The first option is based on continuous aeration in the aeration tank from which the effluent-activated sludge mixture flows to the post-clarification plant. From the post-clarification plant, the activated sludge is pumped sedimented back to the aeration tank and the clarified water flows out from the top of the post-clarification plant.

The second alternative is based on the fact that the entire activated sludge mass is simultaneously in the aeration tank, to which 15 wastewater is fed. However, in this case, there is no separate clarification tank, but rather the tank. the aeration tank also acts as a clarification tank after the aeration has been completed. Once the activated sludge has settled sufficiently, the clarified upper layer, i.e. the purified 20 waste water, can be discharged from the treatment plant (pumping, various floating drainage pipes, etc.). Such a process is called a batch technology and a refinery operating on that principle as a batch process; International abbreviation SBR (Sequencing Batch Reactor). This method 25 is particularly suitable for use when wastewater flows irregularly and for part of the day and / or when the biological specific load of the wastewater is high but the hydraulic load is low. The apparatus operating in the process is also referred to as "shortened activated sludge".

In particular, the use of batch technology has increased in recent years due to its simple operating principle and the good cleaning results achieved. 35 However, the batch process based on the normal activated sludge process has a number of drawbacks which have slowed down its complete breakthrough eg in various wastewater flow situations, malfunctions, cramped installation locations, but also due to its acquisition cost.

First, the batch process is able to receive only the amount of waste water programmed and dimensioned in the norm-5 list. For example, a sudden peak in consumption leads to overflow, which means that only partially treated waste water is discharged from the treatment plant. Avoiding overflow requires additional leveling tanks and additional equipment, thus causing additional costs.

In existing activated sludge plants, including batch purification plants, the purified water is taken from the clarified upper part of the above-ground process tank. If the process is disturbed, this usually occurs immediately. upper layer turbidity, i.e. non-settling solids, various flock populations, etc. If such solids reach the discharge line, it will significantly degrade the purification result of the treatment plant.

The use of the above-mentioned method, which has been in use for over 100 years, for settling activated sludge and removing 25 clarified purified water above, therefore, means that there should not be too much activated sludge to settle sufficiently down within the given time. This further results in the aeration basins becoming relatively large and cannot be reduced without altering the overall operation of the system.

The purpose of the method of the present invention is to provide a decisive improvement on the problems outlined above and thereby substantially increase the state of the art. To accomplish this purpose, the process of the invention is characterized in that the separation and removal of the purified liquid 4 from the activated sludge in the process is effected by passing the liquid at least below the aeration suspended below the activated sludge and associated filtration arrangement. the equilibration and recirculation step of firstly allowing the liquid state of the process space to equilibrate by gravity, through a convergent vessel, through a flow arrangement or part of a flow arrangement as a flow arrangement, and thereafter reactivating

The main advantages of the process according to the invention are, firstly, the process engineering benefits it achieves, in particular because it is possible to scale the volume of the actual process space to a fraction, e.g., about 1/5 to 1/10 of the existing over-clarification basins. Because the removal of purified water occurs through a filtration arrangement, the discharge line never has particles larger than fine particles.

A preferred embodiment of the process is also possible by denitrification and biological removal of phosphorus so that, for example, precipitating chemicals are not required. The operation of the process operating by the method of Kek-30 is still extremely simple and efficient, preferably as a preferred application for monitoring the liquid surface height of the process pool, which provides numerous advantages in process control and practical operation 35. In this case, the method allows for flexible monitoring of large variations in the hydraulic load, by surface-controlled switching of internal recycling and purification of wastewater with 5 intermittent cycles. Thus, no overflow can occur, as in a conventional batch purifier with a process tank already full. Also, possible process malfunctions do not affect the quality of the effluent as easily as with current arrangements. The invention further enables as simple a device technology as possible. a conventional exhaust pump may not be needed. The apparatus 10 operating by the method of the invention has good mechanical reliability, reducing the need for maintenance and maintenance, and furthermore, the reduced overall dimensions provided by the invention imply economic savings.

Other preferred embodiments of the method of the invention are set forth in the dependent claims.

In the following description, the invention will be illustrated in detail with reference to the accompanying drawings, in which Figures 1a, Ib and 1e show three exemplary embodiments of the method of the invention in minor use, and Figures 2a and 2b are longitudinal and top views respectively. a preferred embodiment of the method utilized on a larger scale.

The invention relates to a process for biological purification based on the purification of a process liquid, such as waste water, at least in part by a batch active sludge process wherein aeration of the process liquid, separation of the pure liquid and removal of the purified liquid take place in successive steps. The fluid to be processed is fed to process mode 1 containing activated sludge mass M, wherein the activated sludge mass is aerated 5 at least downstream therewith by aeration system 3 directed through the air distribution arrangement 3 substantially connected to the bottom of the process space to purify the microorganisms in the activated sludge when they use the impurities in the process liquid as a nutrient. In the process, separation of the purified liquid from the activated sludge and removal from the process space 1 is effected by passing the liquid at least downstream of the aeration, through the activated sludge mass M and the associated filtration arrangement 4. The method further comprises an equilibration and recirculation step I, II wherein first the liquid surface of process space 1 is allowed to equilibrate by gravity, through the convergent vessels 20 through the filtration flow 4 through the filtration arrangement 4 and the air distribution arrangement 3 as part of the recycling w to process space 1 to increase its solids mass (MLSS) of active-25 slurry M by re-layering it.

A preferred embodiment of the process according to the invention is that the aeration 30 of the activated sludge mass M is maintained when the liquid to be processed is supplied to the process space 1, that the aeration is stopped before the equilibration step I is started and that the aeration is restarted before the recirculation step II.

In a further particularly preferred embodiment of the method, the level of the liquid surface of the process space 1 is monitored by monitoring means 15, such as the float-controlled control unit 15a shown in Figure 1a to initiate the stabilization step I when the liquid level of the process space reaches its upper limit. In this connection, as a further preferred embodiment, the purified liquid removal step is initiated, preferably within an adjustable time after the completion of the recycling step II, and terminates the process space 1 when the liquid level reaches its lower limit.

In a further preferred embodiment of the method, when the liquid to be processed z is interrupted in process space 1, it is temporarily stored, for example, in the principle x shown in Fig. 2a in the buffer space x in connection with process space 1.

15

Specifically referring to the exemplary alternative embodiments shown in Figures 1a and Ib, regarding the application of the method of the invention in smaller scale operation, the recirculation-20-stage II recirculation is produced by the Mammut principle, producing aeration air by flow arrangement 2; 2a or a flow channel 2 inserted therein as shown in Fig. Ib; 2b or, respectively, to the lower part of the equalizer-25 wire 5, at a distance e from the bottom of the process space 1, and / or by a dotted dash, as shown in Fig. Ib, by a separate recirculating pump 6.

Referring further to the embodiment illustrated in Fig. Le, an alternative or complementary embodiment to the foregoing, a conically expanding top is utilized in process space 1, in particular to reduce the variation in the liquid surface height to facilitate surface adjustment.

Preferably, the process of the invention further comprises a denitrification step 8 and / or a biological phosphorus removal step wherein the fluid to be processed is produced in process space 1 with aeration interrupted for nitrogen removal in an anaerobic condition followed by preferably adjustable shutdown periods, or alternately a recycle and conditioning period (s) of the fluid to be processed to effect biological phosphorus removal in the anoxic state, followed by a suitably adjustable shutdown period if necessary.

In a further preferred embodiment of the method, the oxygen and / or nitric oxide content of the fluid to be processed is monitored in particular to control processing in the denitrification and / or biological phosphorus removal step.

A further advantageous practical application is that it is possible to interrupt the aeration when the fluid level of the process space remains constant for a predetermined period and to restart it when the liquid level of the process space begins to rise, i.e. to produce new liquid.

The dimensioning of the apparatus utilizing the method according to the invention starts with the load SL of activated sludge. It can be selected on the "long aeration process" side from SL = 0.05..0,08..0.1 [kg BOD7 / kg MLSS x d]. In design, the bulk density is OL [kg BOD7 / d / V (i1 - 30 sink) m3] and the relative total amount of activated sludge MLSS [kg / m3]. The interdependence of these factors is well known:

OL

35 SL = -

MT

, hence 9

OL

MLSS = -

SL

Because the method of the invention works by "reversing" the removal of aeration effluent through the aeration filtration layer at the bottom of the aeration basin, the MLSS may be significantly higher than in a conventional clarification-settling process. Again, this results in a high volume of space and hence a "unprecedented" reduction in the volume of the aeration tank:

Biological load LbOD7 V (aeration tank) = - = -

Space load OL

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However, the biological activity of the process remains unchanged and safe when the activated sludge load SL is selected as "safe", as exemplified by the following series: 20 OL 0.3 0.5 0.8 1.0 1.2 1.4 SL = 0.08 = - = - - = - - - = - MLSS 3.75 6.25 10 12.5 15 17.5 1.6 1.8 2.0 25 20 22.5 25 Therefore, if a conventional batch cleaning for example, the spatial load OL = 0.3 and the resulting process state 1 or so-called. aeration tank volumetric index, e.g. 4.0m3 (1.2 kgBOD7 / d), the process according to the invention can be well resolved with a volume: 1.2 kgBOD7 / d V a = = 1.0 m3 35 l, 2kg / m3xd and even more, selecting OL = 2 for a volume of 0.6 m3.

10

Referring to the accompanying drawings, when utilizing the method of the invention, waste water flows freely or is pumped to aeration tank 1, which is in the process of aeration. Compressor C, for example, in the embodiment shown in Fig. Ib, supplies air to the lower part of the center tube 2 / 2b but not to the bottom. The electrically operated valves V2 and V3 at the top of the center tube are closed. The aeration air is distributed evenly through, for example, drainage tube type boreholes 3, where the filter 10 arrangement 4 has a larger scale use e.g. a filter row layer, such as a drain filter sand bed or in smaller implementations e.g. removable dish filter disks.

In order to achieve good cleaning results, the activated sludge should be abundant in relation to the available nutrients, i.e. the activated sludge load SL (= Sludge Load) may, for example, be 0.08 [kg BHK7 / kg MLSS x d) ie. the biological oxygen demand of the incoming wastewater relative to the total amount of activated sludge. Thus, the volume of the aeration tank can be significantly reduced if the slurry of activated sludge (MLSS) is allowed to increase at the same time. The method thus takes advantage of this situation.

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When the aeration tank waste water level reaches the upper limit, the level relay stops the aeration compressor C. According to the principle of converging containers, the effluent slowly rises through the bottom filter 4 while the bulk of the central tube remains in the filter 4 (which functioned as an aerator). After a short wait, the logic center opens the bypass valve V2 and at the same time compressor C starts. The center tube 2b with its air supply is immediately transformed into an air pump (so called Mammut-35 pump), starting to pump aerated waste water via the circulating valve V2 as an upper recirculation w to the aeration tank 1. The suction flow through the bottom filter 4 follows the flow equation 11 V m

(-) = KxT A

The settling and depositing activated sludge forms additional layers continuously, so that the solids content of the effluent leaving the aeration tank is constantly decreasing. After a suitable additional time, the logic relay further opens the actual outlet valve V3, whereupon the circulation water valve V2 closes. Thus, a clean-up waste water discharge step is in progress, which lasts as long as the level relay detects the lower limit and closes the drain valve V3. Compressor C is constantly running, so that the direction of air flow at the same time changes through the bottom filter 4 acting as a filter in the previous step, supplying aeration air to the aeration tank 1. At the same time, this aeration air regenerates and flushes the bottom filter 4. Also, in the larger-scale embodiment 20 shown in Figures 2a and 2b, the aeration is performed by supplying the recirculation flow w preferably with one or more elongated hole or nozzle tubes JP to a wider area on or below the fluid surface of the process space. 1 2 3 4 5 6 7 8 9 10 11

2a and 2b, it is also possible in this connection to utilize 3 auxiliary aerators, such as e.g. a turbine aerator D 4, which is operated on the filter surface as needed to produce additional acidification power by its own rotary motor 6 assisted by a compressor air supply or then without a compressor air supply 7. Because of the separate recirculation pump 6 utilized in the embodiment 8 of Figures 2a and 2b, additional valves V4 and 10V5 have been utilized to perform the desired flow functions in cooperation with the main actuators V2 and V3. Of course, similar types of valve arrangements can also be utilized, e.g., in the embodiments of Figures 1a to 12, when utilizing a separate recirculation pump.

Referring to Figure 2a, the process functions are supplemented by a pump-5 bursting tank X, in which the waste water feed pump has a storage and waiting volume while the internal settling I, recycling II and off pumping steps described above are in progress.

10 Depending on the nature and nature of the wastewater, the duty cycle, for example the level relay difference, can be adjusted appropriately. At the same time, the number of cycles is determined, for example, per day. Thus, the process implemented in accordance with the invention is thus within the scope of the SBR technology, in a sense an intermediate step between the batch technology and the continuous system.

In addition, a logic relay can be used to control the time period during which special denitrification 20 allows denitrification (complete nitrogen removal) and biological phosphorus removal. It is also possible to calculate the amount of wastewater by pulse counting.

Since process control is not necessarily time bound but control based on the height of the aeration tank surface, this should be taken into account in the operating logic. For example, if the surface of the waste water does not change within a certain time, aeration can be stopped. The length of the suspension period depends on the laws of the bioprocess 30. When the surface rises, that is, when new waste water flows in, aeration starts immediately. The situation described is particularly advantageous for the denitrification phenomenon and also for the biological removal of phosphorus.

35 The conditions for dentrification (temperature, pH, and adequate aeration for nitrification) exist with the correct sludge loading (SL) and aeration dimensioning. In addition, the oxygen concentration in the suction step 13 must be brought to the O-level. This is done so that during pumping into the waste water, compressor C is stopped and the downtime is empirically adjusted to a suitable length.

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Biological removal of phosphorus is based on the ability of some bacteria, such as Acinetobacter, to absorb excess phosphorus under aerobic conditions and release it under anaerobic conditions. Thus, biological removal of phosphorus requires a wastewater treatment period in which the water contains no soluble oxygen or nitrogen oxides (anoxic state). In addition, sufficient nutrients must be present.

15 The process cycle of the process is almost the same as above in the denitrification process. The wastewater is pumped in with the aeration interrupted and the wastewater recirculated via the recirculation valve V2. Aeration and recycling now take place in turn.

20

It will be understood that the invention is not limited to the embodiments described or described above, but that it can be modified in many ways within the scope of the basic idea of the invention. Thus, it is clear that the process of the invention can be varied in many respects by using filtration and flow arrangements of a different structural type. Further, it is possible to supplement the method according to the invention with additional control sensors, measuring logics 30 and actuators such as control valves, non-return valves etc. for fine-tuning the process control. In addition, it is also possible to utilize adjustable shutdown or waiting periods between different process steps to stabilize process 35 in the process state. In addition, it is possible to utilize a technique known per se for the chemical removal of phosphorus, e.g. utilizing the co-precipitation method, which means that the precipitation occurs alongside the biological process, rather than as a separate step in which the precipitating chemical (typically ferrous sulfate (FeSO 4) is introduced into the process space.) The precipitated phosphorus must then be removed.

Claims (9)

15 A process for biological purification based on at least partially batch purification of a process liquid, such as wastewater, in which the aeration of the process liquid, the separation of the clean liquid and the removal of the purified liquid take place in successive steps in the same process state. A process space (1) comprising (A) wherein the activated sludge pulp is aerated at least below by 15 aeration air supplied through a flow arrangement (2) substantially connected to the bottom of the process space to purify the process liquid by oxidizing the microorganisms in the activated sludge; impurities in the liquid as a nutrient, characterized in that the process-purified liquid is separated from the active-sludge and removed from the process space (1) is effected by passing the liquid at least below the aeration, downstream, through the activated sludge sludge (M) and the associated filtration arrangement (4), and that, to enhance the process, it comprises an equilibration and recycling step (I, II), first, allowing the liquid surface to equilibrate by gravity, through converging vessels, through a filtration arrangement (4) and an air distribution arrangement (3) through a flow arrangement (v) as a flow arrangement (2) or as part of the settling chamber (5); a process space (1) for increasing the solids content (MLSS) of the activated sludge mass (M) by re-deposition. Method according to Claim 1, characterized in that the aeration 16 of the activated sludge pulp (M) is maintained when the liquid to be processed is supplied to the process space (1), that the aeration is stopped before the equilibration step (I) is started and that the aeration is restarted before the recirculation step 5 (II). Method according to Claim 1 or 2, characterized in that the liquid level of the process space (1) is monitored by monitoring means (15 / 15a, 15b) 10 to initiate the stabilization step (I) when the liquid level of the process space reaches its upper limit. Method according to one of the preceding claims 1 to 3, characterized in that the purification step of the purified liquid 15 is initiated within a certain time after the completion of the recycle step (II) and terminates when the liquid level of the process space (1) reaches its lower limit. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Method 2 according to one of the preceding claims 1 to 4, characterized in that, while the supply of liquid 3 to the process space (1) is interrupted, it is temporarily stored in the buffer space (x) adjacent to the process space (1). 6 7 Method according to one of the preceding claims 1 to 5 8, characterized in that the recirculation (w) of the recirculation stage 9 (II) is produced by the 10 Mammut principle by generating aeration air through a flow arrangement (2), such as by a flow duct 13 (2; 2a or 2; 2b) disposed therein or, respectively, at the bottom of the equilibrium space (5) 14, at a distance (e) from the bottom 15 of the process space (1), and / or a separate recirculation pump (2) 6). 17 Process according to one of the preceding claims 1 to 6, characterized in that the process comprises a denitrification step and / or a biological phosphorus removal step, during which the processable liquid is produced in the process space (1) with aeration suspended for nitrogen removal in an anaerobic state, followed, if necessary, by a period of downtime of a certain length or by alternately recirculating and air-conditioning cycle (s) of the fluid to be processed to effect biological phosphorus removal in anoxic state, followed by a period of downtime of a certain length. Process according to Claim 7, characterized in that the oxygen and / or nitric oxide content of the liquid to be processed is monitored in particular to control processing in the denitrification and / or biological phosphorus removal step. 20 9. A method according to any one of the preceding claims 1-8, characterized in that aeration is interrupted when the fluid level of the process space remains constant for a predetermined time and is restarted when the liquid level of the process space begins to rise, i.e. producing new liquid. Method according to Claim 4 or 7, characterized in that the duration of the shutdown period following the start of the purified liquid removal step following the end of the recycling step II 30 or the anaerobic or anoxic state is adjusted. 18