DE102005013702A1 - Wastewater treatment in a sequencing batch reactor comprises interposing short intermediate sedimentation phases outside of the actual sedimentation/decanting phase - Google Patents

Abstract

Wastewater treatment in a sequencing batch reactor comprises interposing short intermediate sedimentation phases outside of the actual sedimentation/decanting phase. The intermediate phases start between 10 minutes before and 50 minutes after the start of a corresponding charging phase and the amount of wastewater supplied does not cause complete mixing in the reactor.

Description

The The invention relates to a process for wastewater treatment in at least a SB reactor equipped SBR plants, (SBR: sequencing batch reactor), in which the wastewater to be treated in the at least one SB reactor promoted being, being outside the actual sedimentation / decanting phase short sedimentation phases are interposed

at many municipal, industrial and commercial wastewater treatment plants have been a myriad of special procedural steps in recent decades developed and realized the effects on the mud index to be able to examine specifically. It is the primary goal to determine process conditions, among those a stable one. low sludge index is achieved.

This is economical advantageous as the height the mud index over the height the operable activated sludge concentration and / or the hydraulic Throughput capacity decides and thus the decisive parameter for the plant size of the aeration and secondary clarifier or SB reactors.

In an SB reactor, the activated sludge concentration is z. B. TS _R = 5 g / l. The sludge index is ISV = 100 ml / g, the sludge volume SV is then given as 5 g / l × 100 ml / g = 500 ml / l. This means that after a defined settling time of the activated sludge has been reduced to half the reactor volume and the other half is present as a clear water supernatant. At a higher ISV of, for example, 150 ml / g, the mud volume would be 5x150 = 750 ml / L and only a quarter of the reactor contents could be withdrawn as clear water, ie the hydraulic throughput capacity of this higher mud index reactor would be only half that of Reactor with the smaller mud index.

Besides that is a stable low sludge index ecologically very beneficial, because at high sludge indices there are big problems like floating and bulking sludge formation result. These sludge fractions with a comparatively high sludge index often arrive in the receiving waters uncontrolled and cause there considerable water pollution.

moreover to lead increased Sludge drifts to correspondingly higher effluent concentrations, in particular of the wastewater taxable parameter COD (: chemical Oxygen Demand). This then results in higher wastewater disposal costs and ggfl. also fines.

ever by type of commercial influences can favorable or unfavorable Effects on the sludge index occur. For example, they work vineyard wastewater often unfavorable out. Even lower mud ages often have an unfavorable effect the mud index. Operating modes with burst feed In contrast, they predominantly affect positive for the sludge index.

Basically but that even when realizing many or all of the positive factors Also high sludge indices can result and sometimes even low Mud indices under unfavorable Conditions occur.

Also a number of special factors, such as anaerobic, anoxic and aerobic selectors and adding different precipitants and flocculants are been examined in their effects on the sludge index. Sometimes positive and sometimes negative effects were noted. Again, no positive effects were found in any case What: For many plants, a reduction in the sludge index led, effected almost nothing at other facilities and even affected some negative.

To The most stable positive factors include the realization of the feast / famine Principle of SBR systems, unfortunately, there are also some large-scale Counterexamples.

since some years ago, process conditions are developing that way called aerobic granular Flakes leads, intensively examined. This is a special one Type of activated sludge in SBR plants with an extremely low sludge index from 15-40 ml / g.

meanwhile are for this from an economic point of view viable process techniques have been developed that a right ensure stable activated sludge population at least on a laboratory scale. However, the COD effluent concentration from such plants is unacceptable high and must be reduced with subsequent cleaning steps. These too high COD values always occur when falling below one Sludge indexes in granules of about 40 ml / g.

All of the above methods are aimed at realizing process conditions that more or less indirectly exert positive selection pressure on rapidly settable flakes. This is therefore often (but not always) possible because the activated sludge of all plants consists of a mixture of different quickly deductible flakes. The measured mud index is therefore a kind of means worth about the flake structure of all the flakes of a basin.

• 1) entweder aus dem vollduchmischten Behälter die Entnahmen erfolgen und somit zwischen den Flockenfraktionen keinerlei Unterscheidung erfolgt oder
• 2) während bzw. am Ende der Sedimentationsphase die Überschussschlammentnahme im Bereich der Reaktorsohle erfolgt und somit tendenziell sogar Fraktionen mit überwiegend guten Absetzeigenschaften entnommen werden.

These framework conditions are indirect as far as in all previously implemented forms of excess sludge sampling from SBR reactors

• 1) either from the vollduchmischten container take the withdrawals and thus no distinction between the flake fractions takes place or
• 2) takes place during or at the end of the sedimentation phase, the excess sludge removal in the reactor bottom and thus tend even fractions are taken with predominantly good Absetzzeigenschaften.

The however, the factors which determine the floc structure are such diverse and also largely unknown in their mutual behavior, so that again and again, even in the case of the most favorable conditions, the plant "overturned" and within a short time Time a high sludge index arises.

In WO 93/04759 and the US 5,395,527 It is proposed to carry out the feeding of the reactors more or less flat on the reactor bottom a certain time after the beginning of the sedimentation phase. Thus, the raw sewage is pushed from below through the sedimented activated sludge bed. With this specific form of the feed a certain time after the beginning of the sedimentation phase, the clear water supernatant is displaced or decanted at the same time, ie this feed is integrally coupled to the decantation and can only begin after a certain sedimentation time, so that the displaced batch consists only of purified clear water.

In order to will most likely have a positive impact on the Mud index exercised. Indeed is the execution a nearly sole-flat Reactor feed very expensive and some non-reactive sedimentation time (about one hour) must wait before the start of the loading, so that a sufficient clear water supernatant has formed.

In The 10 2005 007 408.1 is proposed by a controlled Charge at the beginning of the actual sedimentation predominantly the Low-sludge index fraction to a positive selection pressure suspend.

task It is therefore an object of the invention to provide a method in the context of all or some feeds outside the actual sedimentation a directly positive selection pressure on the predominantly Low-mud index fraction is exercised, possibly without good indirect conditions, as described above, are present.

The Invention is solved solved by a method having the features of claim 1, the dependent claims advantageous embodiments of the method.

These Must have feeds thereby take place in the lower reactor area and predominantly in the lower layers (in which the sedimenting sludge falls down) remain or be stirred into it.

Unlike the method of the DE 10 2005 007 408.1 According to this method, it is completely sufficient to ensure that the raw sewage of the feeds predominantly remain in the lower reactor area in the course of the intermediate sedimentation phases, thus ensuring that the raw raw sewage fed in does not reach the above-formed clear water layer under any circumstances the fastest settling mud flakes are mixed on average more strongly with the raw sewage supplied, as the upper flake fractions, which consist on average of slower settleable flakes.

These Feeding therefore preferably takes place at only one point in the peripheral region of the reactor bottom in horizontally same direction like the movement of the reactor contents (which due to the inertial principle the mass after stopping the Umwälzeinrichtungen stir for some time). Of the Beginning of these intermediate sedimentation phases takes place 10 minutes before 50 minutes after the beginning of a corresponding charging phase in the reactor and can until the beginning of the next Ventilation phase persist.

A further preferred embodiment The invention is as described above, but with several Supply locations. For example, the peripheral is in the sole area horizontal guided Feed line provided with several tangential openings, which ensure that the water leakage predominantly horizontally in the flow direction the reactor contents. Compared to the first embodiment can thus a significantly higher load be realized without a breakthrough in the upper forming Clear water takes place.

The advantage of this type of process is therefore that this specific form of the feed generates a reaction space below the settling sludge volume, in which both the activated sludge concentration and the pollutant load concentrations are greatly increased. This reaction kinetic has great advantages for the corresponding reaction rates.

Furthermore arise big Benefits for the Effects on the floc structure: the higher the wastewater concentrations are (analogous to the plug flow principle) the more positive are the effects on the sludge index, i. the more compact mud flakes become positively selected and it forms a comparatively lower Sludge index.

This Advantage is reinforced by the fact that the fastest settling mud flakes (i.e. contribute to a particularly low sludge index) in the statistical Apply medium in the lower part of the mud bed, in the area So, in which the raw sewage least with the reactor contents dilute becomes. This will be the fastest settling mud flakes the strongest positively selected and the setting of a low sludge index promoted.

This Method can also be realized with upstream of one or more buffer tanks.

Without upstream buffer tank the entire feed effluent has to be pumped into a reactor. In this case, need the supply line (s) in which the reactor (s) are formed so that the feeds not in itself lead to a complete circulation of the reactor contents.

With Pre-connection of one or more buffer tanks, the reactor feeds on the other hand almost freely chosen are largely decoupled from the current feed quantities. Therefore can also the feeds at the beginning of sedimentation by a corresponding adapted control of the promotion be designed so that there is no complete revolution.

Claims (4)

Method of wastewater treatment in one with at least a SB reactor equipped SBR systems, in which the wastewater to be treated in the at least one SB reactor promoted being, being outside the actual sedimentation / decanting phase short sedimentation phases be interposed, characterized by a beginning of Intermediate sedimentation phases 10 before to 50 min after the beginning of a corresponding feed phase in the reactor, wherein the feed rate alone not complete Reactor mixing causes. Method according to claim 1, characterized in that that the intermediate sedimentation phase until the beginning of the next ventilation phase ongoing. Method according to Claims 1 and 2, characterized that the feeder only at one point in the peripheral region of the reactor bottom in horizontally the same Direction as the movement of the reactor contents takes place. Method according to Claims 1 and 2, characterized that the feeder in several places in the form of tangential feeds / openings in the peripheral area the reactor bottom in the same horizontal direction as the movement the reactor contents.