DE3017439A1 - Biological waste water purificn. - with addn. of density-controlled open hollow bodies allowing abrasion-protected bacterial growth - Google Patents

Abstract

Biological waste water is purified by using solid bodies which are kept in flotation and in constant motion and to which there adheres a bacterial growth. Excess bacterial growth is removed, to leave sufficient growth for purificn. process as a thin bacterial surface layer. Novelty consists in adding open hollow bodies to the waste water-activated sludge mixt. of a standard activation tank, in the presence of O2. Hollow body specific gravity is selected to suit that of mixt. and its flow-form, so that they are driven in flow. Hollow body shape and size is selected so that inside them the bacteria find a growth-surface protected against mechanical abrasion. The process is used esp. for purifying conc. industrial waste waters. The advantages of activated sludge and trickle filter processes are combined in one reaction tank. Microorganisms having different purificn. properties can be cultivated in one activation tank. Easily- and difficultly degradable materials can be decomposed in one working step, including nitrifying and denitrifying of N cpds. Clarifying plant can be restored by hollow body addn.

Description

The invention relates to a method for biological purification

Treatment of wastewater using solids that are in suspension and kept in constant motion and on which there is bacterial growth adheres, the excess bacterial growth is removed so that a sufficient growth in the form of a thin layer of bacteria for the cleaning process remains on its surface.

In aerobic biological wastewater treatment, the natural Technically simulated biological self-cleaning processes occurring in bodies of water. In these technical processes (activated sludge and trickling filter processes) a closely limited section of a natural habitat modeled. Instead of the to let the entire "eating chain" run, it is here after the 2nd or 3rd

Member, the protozoa or rotifers, by removing the organisms broken off in the form of mud, because only the first links are for the direct Removal of pollutants from the water is responsible.

About the aerobic biological processes as they occur in self-cleaning of the natural waters, for temporally and spatially limited reactions In order to make it usable, the following conditions must be observed: 1. The wastewater constituents biological bacteria must be accessible, 2. oxygen must be taken from the air can be, with concentrations above 2 to 3 mg 02/1 on the biological cleaning process are without influence, 3. biologically active substance, doh. Microorganisms, predominantly Bacteria and protozoa, the organic substances contained in water under aerobic conditions Binding to itself adsorptively and absorptively to build up cell substance or as an energy source consume, must be present, 4. a good distribution of waste water constituents, Oxygen and microorganisms in the reaction space, as well as a quick change the contact areas between # organically polluted wastewater and small organisms must be guaranteed and 5. the response time must be sufficient.

The aerobic biological wastewater treatment is nowadays in two main processes as well as some variations of these procedures: a. the activation process, b. the trickling filter method.

To a.) Activation process.

The technical system driving this process consists of the biological one Reactor, the so-called activated sludge tank, and a settling tank, the secondary clarifier, in which the revitalized mass in the form of sludge from the treated wastewater passes through gravity separates.

The settled sludge, the actual carrier of the cleaning performance, is continuously withdrawn at the bottom of the funnel of the sedimentation basin and to further Degradation feed returned to the aeration tank. So the mud is constant in the cycle. Only the sludge increment is removed as excess sludge.

Regarding b.) Trickling filter method.

The trickling filter is a copy of the top soil layers in technical terms Scale, due to the ground clearance and the pore volume, the oxygen supply guaranteed by air currents0 on the surface of the rock material can - just like with the soil particles - an aerobic community to settle.

Trickling filters consist mainly of rocks or slag, the ~ filler material ", with a larger proportion of voids o Distribute on round trickling filters mostly rotary sprinklers, which are kept in motion by the recoil of water, the pre-clarified Sewage over the surface. Rectangular, hexagonal or octagonal trickling filters can can be fed with fixed or mobile distributors.

The trickling water is underneath the trickling filter base collected in a grate and drained into gutters. The hollow floor and the one between the Chunks of remaining gaps allow oxygen delivery from the vertical through air sweeping the trickling filter. The microorganisms adhere to mucous membranes as biological turf on the filler material. Also removing the undissolved contaminants from the wastewater happens in the trickling filter with the larger cavities between the Broken not by filtering, but by adsorption on the biological lawn Dem Trickling filters are usually followed by a sedimentation basin in the drain to keep the sludge parts of the rinsed biological lawn away from the receiving water.

In the activation process, the excess sludge becomes continuous or discontinuously removed from the activated sludge tank - secondary clarifier system, Das Mud age, which is largely responsible for substances that are difficult to degrade is, becomes smaller with increasing load, because the sludge age results from the ratio of the amount of sludge working in the aeration tank to the amount of sludge removed daily Excess sludge.

This is taken into account in a two-stage recovery system. It two biozenoses with different properties are used. Be there in the first stage predominantly the easily degradable carbon compounds and in the second stage the more difficult to break down nitrogen compounds are broken down. For this however, an intermediate clarifier is required.

For a cleaning with nitrogen oxidation are therefore with the one-stage Treatment of large pelvic volumes with the resulting large residences and ventilation times required. In the case of a two-stage system, the aeration tank content can be used must be kept smaller, but an additional intermediate clarification is then inevitable.

In the trickling filter process, the biological lawn has due to its Age the properties required for the breakdown of more difficultly degradable substances are. The possible cleaning performance in a reactor (aeration tank as well as Trickling filter bed) depends on the product of the biologically active substance and the reaction time. However, the reaction time in a drop is relatively short (10-30 min.). With the trickling filter method is also a 3 times longer residence time in the primary treatment (3 times the tank volume) than necessary for the activated sludge process because of the risk of clogging the trickling filter.

While in the activation process there are significant influences (bacterial density, Return sludge, oxygen supply) are to be regulated operationally, are in the trickling filter the most important operating data are already defined during the dimensioning.

In the case of the goblet method, there is also an edge effect in some areas (Niches and deeper layers) Lack of oxygen. this has with weakly polluted trickling filters a reduction in the total nitrogen es up to 25 ffi result. Higher values can only rarely be achieved and not in the process controllable.

Immersion trickling filters have so far been in an order of magnitude between Proven to be equivalent to 10 and 15,000 inhabitants. They are, however, very high Oxidation times required. The principle is the same as with the float method (DE-OS 23 66 033) on bringing organism growth areas into the wastewater.

The size of these areas remains far behind that of the Float method possible back.

These recent developments have the disadvantage that they are special Need reaction vessels and / or special agitators. So you are not or not to be used in existing systems without great effort.

In none of the procedures is oxygen starvation allowed or conscious generated, denitrification in the process step is therefore not possible.

The invention is based on the object of the advantages of the activation and the trickling filter process in a reaction basin and the To create the conditions for microorganisms in an aeration tank can be raised with different cleaning properties, with which Easily and poorly degradable substances can be broken down in one operation, including Nitrification and denitrification of nitrogen compounds.

The object is achieved according to the invention in that the waste water / activated sludge mixture an aeration tank of known type in the presence of oxygen open hollow bodies admitted whose specific weight is adapted to that of the mixture and to whose flow forces are chosen so that they float in the flow, and their The shape and size is chosen so that the bacteria in their interior have a mechanical resistance Find abrasion-protected growth areas. With a fixed specific weight control the suspension by the return sludge ratio.

For simultaneous nitrification and denitrification in the aeration tank The following properties of the bacteria are used: In natural waters -are A number of facultatively anaerobic bacteria are involved in self-cleaning, i.e. ~ 3acteria that use both elementary and bound oxygen. If there is a lack of free oxygen in the water, such bacteria are able to bind Oxygen from nitrites, ritrates and sulphates for the anaerobic oxidation of organic Use carbon compounds.

You can use both nitrate oxygen and elemental oxygen Oxidize carbon compounds, such as the Pseudomonas species P. fluorescens, P. aeruginoss and P. denitrificans.

Typical facultative anaerobic nitrogen utilizers are Iroteus vulgaris and Escherichia coli. Some bacteria can be heterotrophic in terms of nitrogen sources or be autotrophic; E.g. Escherichia coli uses het-erotroph protein, peptones, Amino acids, autotrophic ammonium, P. fluorescens utilizes the same organic N sources, as well as ammonium and nitrate. Most nitrate reducers are also heterotrophic, which anaerobically reduce nitrate to molecular nitrogen, such as Micrococcus denitrificans.

F.W. Siepmann wrote in his diploma thesis at the T.H. Darmstadt proven, that the described anaerobic nitrate reduction in the sediment of a river bed also then expires when there is still oxygen in the water. This is due to, that in the cavities on the sole and in deeper cell layers on the stones there will always be zones with a lack of oxygen, depending on the oxygen content of the surrounding water.

In bodies of water, the one in the test arrangement comes under the exclusion of light measured effect just does not come into its own because ammonium and nitrate are constantly over algae and higher plants are built into the nutrient cycle and at night when there is no light, and in over-fertilized rivers there is no oxygen for oxidation via nitrite too nitrate is absent.

The invention makes use of these findings. The aeration tank float system represents the river system - bottom cavities - overgrown stones.

In the short term as well as in the long term, there are alternating states of breathing of the facultative anaerobic bacteria due to the float shape, their position in the Current and occur locally in the aeration tank, namely: In the rotating Flow are the flowing and driving floats with a statistical distribution once from the open side, the other time from the closed side and also hit by the oxygen-enriched flow in all other positions, i.e.

once the oxygen reaches the biological growth directly, a other times only via diffusion.

In the case of the floats, there is a statistical distribution different densities of vegetation with different oxygen supply. The growth within the float will grow as long as until the lower bacterial layers die and are washed away by the current.

Since the flow is not stationary, it is for individual floats the time from ventilation to ventilation - again with statistical distribution - varies in length.

In a further development of the invention, the cavity is through the hollow body Slats divided into niche-like sub-spaces.

As a result, the colonizable surface is multiplied.

The type of respiration is determined by the number of lamellae within the hollow body the facultative anaerobic bacteria also influenced.

Compaction of the lamellas means increasing the anaerobic area.

In an advantageous embodiment, the hollow bodies are spherical caps a ~ 2 c D - <15 cm and a height H = D / 2 + 0.25 cm. The number n of lamellas should be 0.5 between D i n L 2D.

By varying the ball diameter and the arrangement of the operating density111 # the growth area can be varied in a wide range. The size of the Lamellenhaibkugeln is limited at the bottom by the fact that they are not in the secondary clarifier be allowed to absolutely swim. For this purpose, sieves of the appropriate hole size are at the outlet of the Provide aeration tank.

1) Operating density equal to 1 means balls in the loosest ball packing stored, operating density equal to 0.5 means half as tight as the loosest spherical packing stored.

To produce the lamellar hemispheres, POLYAMIDE or in the Properties of comparable plastics with a specific weight between 1.0 and 1.03 g / cm3, depending on the nature of the wastewater-activated sludge mixture, Find use.

The following ratios should preferably be selected.

a) Bacteria activity predominantly in the aerobic area: D = n / 2 (D in cm) D = diameter of the hemispheres (H = D / 2) n = number of lamellae per hemisphere The specific surface area per m3 with the loosest spherical packing (loosest spherical packing equal to 52 r # volume per m3) is then: For the benefit of greater freedom of movement for the individual floats, less than the loosest ball packing should always be used.

Small ball diameters favor the exchange processes within the lamellae and thus aerobic degradation.

b) Substrate degradation with increased denitrification: The lamellae in between serve as "denitrification niches" 1.

The degree of denitrification is based on the oxygen content in the aeration tank controlled and should not be above 3 mg / l.

In biological stages with extensive nitrogen oxidation takes place denitrification as an unwanted effect in the settled sludge of the secondary clarifier instead of. Unintentional because rising nitrogen gas expels the sludge and it swims over the spout.

In the method according to the invention, this process takes place in the for it provided "denitrification niches" of the hollow body instead. It becomes a conscious one Oxygen bottleneck generated within a portion of the hollow body.

The nitrification and the breakdown of poorly degradable substances is of the remaining, predominant part of the aerobically working bacteria.

The process is particularly suitable for cleaning concentrated Industrial wastewater, because of the shape, size and operating density of the invention Float the openable area is very large compared to other methods can be chosen. In addition, it is possible to "readjust" by adding more Hollow bodies possible.

Another advantage is that existing sewage treatment plants with overloaded aeration tank by adding such hollow bodies, in particular lamellar hemispheres can be easily refurbished.

Significant construction and operating costs can be saved for new systems will be through a) more economical use of the registered Oxygen, since it does not get into the water, especially in the case of aeration tanks with pressure aeration transferred air bubbles adhere to and in the hollow bodies and thus a longer one Remaining time in the water, b) reduced return sludge costs, c) saved it basin volume by increasing the active biomass and thus shorter Ventilation and residence times.

The following combinations of processes are possible: For concentrated Industrial wastewater (dairy, slaughterhouses, etc.) Use of the float without the use of return sludge and control of the degradation a) predominantly aerobic, b) aerobic and anaerobic.

Use of the float for domestic and industrial wastewater mixtures with the usual activated sludge process and control of the degradation a) predominantly aerobic, b) aerobic and anaerobic.

A calculation example is given below.

In the calculation: Q = amount of water d = days BOD5 = biochemical Oxygen demand, i.e. the amount of dissolved oxygen required for the oxidative biological Degradation of organic substances in the water in 5 days is required TSR = solids content in the aeration tank BTS, HR, Q / 18 = design guide values TS = dry matter One Municipality whose wastewater quality has increased in recent years due to brewery, dairy and wastewater from large farms has deteriorated significantly, is to be rehabilitated.

Data: Q = 9333 m3 / d design BOD5 - 600 mg / l design BOD5, separated = 420 mg / l design quantity = Q / 18 BOD5 - load = 420 mg / l 9333 m3 / d aeration tank V = 1200 m3 dry sludge substance TSR = 3 kg / m3 BOD - freight sludge load BTS = 5 BS35 / d = kg BSB5 kg TS od 3920 - kg BSB5 residence time t w 7 = 1200 = 2.3 h Auf eit t = Q / 18 9333/18 i.e. heavily loaded aeration tank, efficiency approx 72%.

Remediation: Complete cleaning with nitrogen oxidation. Division of cleaning in two stages.

The existing system works as the 1st stage, the 2nd stage is the float admitted.

The assessment of the cleaning performance of the 2nd stage is derived from the cleaning performance derived from trickling filters (see table).

Br, erf 0.4 kg BOD5 / m3.d BOD / d BR (kg BOD5 / m3.d) cleaning performance (kg m² m 0.2 0.0025 0.3 0.00375 0.4 0.005 0.5 0.00625 0.6 0.0075 0.7 0.0088 0.8 0.01 contact time: 10 - 30 min.

Well comparable values are also found in bodies of water for organisms drifting sand grains have been measured.

How many m2 of growth area must be added? 3920. (1 - 0.72) = 1114 kg BOD5 / d must be broken down from the second stage.

1114 kg BOD / d 2 222 800 m2 5 222 800 m 0.005 kg BOD5 / dm required Fspec. - 222 800 m² - 185.66 1200 m3 m² / m³ Selected: D # 5 cm, hemisphere spec. area with loosest packing of spheres Per m³ = 282.7 2 67.5% of the loosest packing of spheres inserted: 282.7 ~ 0.675 o 1200 = 229 255 m i.e. take the lamellar hemispheres in the pool without water 0.52 ~ 0.675 = 0.35 = 35 # of the pool volume.

The values for the reduction in total nitrogen are also used a comparative drainage filter was used.

With about five times the time spent in the calculated aeration tank to be on the safe side, the trickling filter values are compared to the dripping time for the trickling filter only tripled.

Reduction in total nitrogen: 25%. 3 = 75% The bill is on on the safe side in all points.

The attached diagram shows the proven by measurements Relationship between the oxygen content of the river water and the decrease in nitrate nitrogen during the test period in the closed control volume of the measuring device with a simultaneous decrease in total nitrogen for various sands and gravels.

The measuring device for determining the oxygen consumption of sedentary people Organisms in bodies of water under natural conditions is part of the thesis described.

The drawing shows an example of a lamellar hemisphere in plan view and side view in natural size with the values D = 7 cm, H = D / 2 and n = 8 as well as a wall thickness of 1 mm.

Claims (1)

Process for the biological purification of wastewater Patentanænrüche 1 Process for the biological purification of wastewater using solid bodies, which are kept in suspension and in constant motion and on which a bacterial growth adheres, with the excess bacterial growth such is removed that a growth sufficient for the cleaning process in the form of a a thin layer of bacteria remains on its surface, characterized by that the sewage-activated sludge mixture of an activated sludge basin is known in the art Presence of oxygen open hollow bodies are added, their specific Weight in adaptation to that of the mixture and its flow forces as above is chosen that they float in the current, and their shape and size so chosen is that inside the bacteria are a against mechanical Find abrasion-protected growth areas. 2. The method flat to claim 1, characterized in that the cavity the hollow body is divided into niche-like sub-spaces by lamellae. 5. The method according to claim 1 or 2, characterized in that the specific weight of the hollow body is in the range from 1.0 to 1.03 g / cm3. 4. The method according to claim 1, characterized in that the hollow body Calottes of a ~ 2 <D D # 15 cm and a height H = D / 2 + o 255 cm. 5. The method according to claim 2 and 4, characterized in that the number of lamellas between D n <2D, # is selected as an integer.