SK282315B6 - Small-scale biological sewage treatment plant - Google Patents

Abstract

The invention concerns a small-scale biological sewage treatment plant operated by fluid bed/biofilm technology for treating waste water. According to the invention, for the biological/biofilm treatment of the activated sludge a biostage (2) with an aeration device (4) which can be switched off is arranged downstream of a preliminary sedimentation tank with a sludge reservoir (1) and a feed pipe (6). The biostage (2) is partially filled with growth bodies (5) having a colonizable area of at least 800 m<2> per m<3> of bulk volume and comprises a retention device (8) for retaining the growth bodies (5) in an obstruction-free manner. Disposed after the retention device (8) is a final sedimentation tank (3) which can be flowed through vertically and has a discharge (7), the parts of the plant (1 to 4) preferably being disposed in circular tanks. The retention device (8) can consist of a pipe in or over which a discharge pipe leads into the final sedimentation tank (3). The biostage (2) can further comprise a biofilter stage (9) into which lead the feed pipe from the preliminary sedimentation tank (1) and the feed pipe for returned sludge from the final sedimentation tank (3). The specific weight of the growth bodies can be greater or less than 1.0 g/cm<3>.

Description

Technical field

The invention relates to a small-capacity biological treatment plant comprising a pre-treatment and sludge storage tank equipped with a wastewater inlet and downstream of a biological stage with activated sludge biology / layer biology and a detachable aeration device partially filled microorganisms which are cultivated with culture means, in which a containment device is arranged for holding the culture bodies and is connected to a purification tank with a flow in the vertical direction, which is equipped with a drain, and parts of the small-capacity cleaning device are located in a circular tank.

BACKGROUND OF THE INVENTION

According to the state of the art of wastewater treatment, the cleaning performance and process stability of small-scale treatment plants are insufficient.

The main reasons for this are:

- fluctuating and mostly low biomass concentrations,

- instability of biomass,

- Extraction of biomass in hydraulic shocks

- unstable reintroduction of biomass from the treatment plant to the biological stage,

- lack of peak load balancing capacity,

- biomass discharging and thus a decrease in low-load performance and waste water scarcity,

- a decrease in pH as a result of nitrification and, as a consequence, a delay in the biodegradation processes.

For example, in order to increase the cleaning performance and process stability, the biological stage of the small cleaning equipment is equipped with a packet fixed bed on which microorganisms settle. These microorganisms are then not released even in the case of hydraulic shocks. The shortcomings of these technologies are:

- the settable surface of fixed beds, which is 100 to 150 m ² per m ^{3 of} biological degree, is relatively small. As a result, the cleaning capacity or load capacity per m ³ of the tank volume is also low.

- Fixed bed surfaces are usually overgrown with relatively thick layers of biomass. Since only the topmost layer of biofilm is adequately supplied with oxygen and nutrients, its bioactivity is limited.

- Rotation processes occur inside the grown biomass layer, which also adversely affects the potential cleaning performance due to the death of microorganisms.

- Deposits on packet fixed beds and their clogging both inside and outside limit the settling area and thus the biofilm performance.

- Fixed bed cleaning is only possible at the expense of increased maintenance costs.

In a research report of the Federal Ministry of Research and Technology, 02 WA 8538 of October 1987, there is information on the use of whirling floating bodies to increase the capacity of cleaning equipment. Compared to packed fixed beds, the settable surface per unit volume of the tank is noticeably larger.

However, there are unsolvable problems with the retention of the floating bodies at the biological stage. The bodies are partially retained by a rake. In addition, these bodies are clogged so that they sink to the bottom and settle on this day.

It is also known to use vortex culture bodies to increase the amount of biomass in purification plants. The retention of the bodies is carried out by sieves or rakes.

In view of the high proportion of fibers and suspended particles in municipal waste water, this type of retention of the bodies must clog with clogging and clogging, and consequently emergency situations, after a short period of operation.

WO-A-95 17351 discloses an aerated tank comprising a fluidized bed of particulate carrier material. US-A-4,421,648 discloses an apparatus and method for biological treatment of waste water with a purified water flow in the purification tank in a vertical direction.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a small-capacity biological purification apparatus, in which the aforementioned drawbacks of known apparatus of comparable size are largely eliminated.

SUMMARY OF THE INVENTION

The problem is addressed and the shortcomings of similar small-scale biological treatment plants are largely eliminated by a small-capacity biological treatment plant consisting of a pre-treatment and sludge storage tank equipped with a waste water inlet followed by a biological stage with activated sludge biology / biology. layers and a detachable aeration device, which is partially filled with microorganisms which can be revived with cultivation bodies, in which a containment device is arranged for detaining the cultivation bodies and is connected to a purification tank with a flow in the vertical direction, equipped with a drainage device. A circular tank according to the invention, characterized in that in the biological stage there is additionally placed a biological filtration stage, into which the inlet from the routine water purification and sludge storage and re-introduction of sludge from the purification tank.

The density of the culture bodies in the first variant is less than 1.0 g / cm ³ and preferably is 0.9 g / cm ³ , both inlets from the pre-treatment and sludge storage tank and from the purification tank being located at the top of the biological filter and the tube of the containment device extends from the bottom of the biological stage to the water level.

In a second variant, the density of the cultivation bodies is greater than 1.0 g / cm ³ and preferably is 1.1 g / cm ³ , both inlets from the pre-treatment and sludge storage tank and from the treatment tank being located at the bottom of the biological filter and the pipe of the retention device extends at a distance from the bottom of the biological step up to the water level.

The cultivation bodies have a settable surface of at least 800 m ² per m ^{3 of} bulk volume. The retention of the culture bodies in the aerated biological stage, with the exclusion of the risk of clogging, takes place on the following two principles:

Option 1: Cultivation bodies with a specific gravity of less than 1,0 g / cm ³ :

A sealed and top-open tube is placed in the aerated biological stage. The pipe ends approximately 30 cm below the surface of the water. The diameter of the pipe depends on the amount of water passing through. A second smaller diameter pipe is connected to this outlet and is connected to the outlet. This second smaller diameter pipe starts approximately 30 cm above the bottom of the larger diameter pipe and ends above the water surface.

This solution ensures that the culture bodies with a specific weight of less than 1.0 g / cm ³ in a pipe of larger diameter continuously flow back into the swirl bed.

The recovered sludge and purified wastewater flow through the smaller diameter inner pipe into the purification tank.

Option 2: Cultivation bodies weighing more than 1,0 g / cm ³ :

At both ends, the open tube begins above the surface of the water and ends approximately 30 cm above the bottom of the biological stage.

A smaller diameter pipe is inserted from below into a larger diameter pipe. This pipe begins below the surface of the water and ends with a drain from the biological stage.

This solution ensures that the cultivation bodies with a density greater than 1.0 g / cm ^{3 are} continuously returned to the whirling bed. The activated sludge and purified water flow through the inner pipe into the purification tank.

Both tubes are sized so that the cultivation bodies cannot be removed from the biological stage even under high hydraulic loads.

The recovered sludge separated in the purification tank is partly pumped back to the biological stage. The excess sludge produced, together with the primary sludge, which is separated during pre-treatment, is stored until withdrawal in the pre-treatment and sludge storage tank.

Significant differences from the prior art are as follows:

- In the aerated biological stage of the purification plant, cultivation bodies are used whose settable surface, which is more than 800 m ² / m ^{3 of} bulk volume, is several times larger than in fixed bed installations with known cultivation bodies.

- The size and shape of the cultivation bodies are such that clogging and settling can be excluded.

- The biological layer on the cultivation bodies is thin and therefore physiologically very active due to their continuous rubbing in the whirling bed.

- The supply of oxygen and nutrients to the micro-organisms in the biological layer is optimal. Rotting processes cannot occur. The cultivation bodies are maintenance-free,

- Microorganisms grown in the mica layer on cultivation bodies are resistant to even a long-term lack of new wastewater and transient oxygen deficiency.

- The cultivation bodies have a specific gravity of either less than or greater than 1 g / cm ³ .

- The retention of the culture bodies in the fluidized bed through which the waste water passes is ensured without the risk of clogging.

-1, it is difficult to remove the cultivation bodies when the cleaning device is hydraulically overloaded.

- The cleaning performance is stable even in the case of hydraulic shocks and heavy fluctuations in the content of impurities in the waste water.

- The recovered sludge is separated in a known manner by sedimentation in the after-treatment tank and is partially returned to the biological stage. Due to the combination of both technologies, the biological stage can be more burdened and a high stability of the wastewater treatment process is ensured.

- Due to the arrangement of the anoxic stage in the biological stage, nitrogen is largely eliminated by biological nitrification / denitrification processes.

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS The invention is further elucidated with reference to the accompanying drawings, in which:

FIG. 1 small-capacity biological treatment plant with cultivation bodies of less than 1,0 g / cm ³ ,

FIG. 2 a small-capacity biological treatment plant with cultivation bodies having a specific gravity of more than 1.0 g / cm ³ .

DETAILED DESCRIPTION OF THE INVENTION

The individual stages of the small-capacity biological treatment plant are preferably arranged in a circular concrete tank, which is divided into three segments. The raw waste water first flows into the first segment, which serves as a tank 1 for preliminary water purification and sludge storage, in which the waste water is freed of coarse and floating dirt and sand. The waste water then enters biological stage 2, which is partially filled with culture bodies 5 and equipped with an adjustable aeration device 4. At the same time, biological sludge from the purification tank 3 is reintroduced into biological stage 2.

The culture bodies 5 form a whirling bed when the air is introduced, while forming a layer with an anoxic environment when the aeration is disconnected.

In particular, as wastewater passes through this biological stage 2, dissolved organic substances (biological oxygen demand, CSB) are degraded aerobically and nitrogen is partially eliminated in the biological phases of nitrification and denitrification.

The culture bodies 5 together with the microorganisms deposited thereon are retained in the aerated biological stage 2 without the risk of clogging.

The suspended biomass, i.e. the recovered sludge, is separated from the purified water in the purification tank 3 with inclined walls and with a flow in the vertical direction. Part of the sedimented recovered sludge is continuously fed back to biological stage 2. The excess biomass is pumped intermittently to the pre-treatment tank 1 and sludge storage.

Sludge resulting from mechanical pre-treatment and biological treatment is collected until collection and anaerobically stabilized in the pre-treatment tank 1 and sludge deposit.

Biological step 2 is provided with an un aerated biological filtration step 9, which is filled with culture bodies 5 and serves as a denitrification step. This biological filtration stage 9 introduces the recovered sludge, which is fed back from the purification tank 3, and the water discharged from the tank 1 for preliminary water purification and sludge storage.

The anoxically pre-treated wastewater enters the aerated portion of the biological stage 2 after passing through the biological filtration stage 9.

Claims (3)

PATENT CLAIMS 1. Small-scale biological treatment plant, consisting of a tank (1) for pre-treatment of sludge and sludge storage, which is equipped with a wastewater inlet (6) followed by a biological stage (2) with activated sludge biology / layer biology and detachable an aeration device (4), which is partially filled with microorganisms which are capable of being revived by cultivation bodies (5) having a settable surface of at least 800 m ² per m ^{3 of} bulk volume, in which the containment device (8) is located and connected a purification tank (3) with a flow in the vertical direction, which is provided with a drain (7), the parts (1 to 4) of the small-capacity cleaning device being located in a circular tank, characterized in that in the biological stage (2) filtration stage (9), into which the inlet from the tank (1) for the preliminary purification of water and supplying the sludge and supplying the recycled sludge from the purification tank (3). A small-capacity biological treatment plant according to claim 1, characterized in that the density of the culture bodies (5) is less than 1.0 g / cm ³ and preferably is 0.9 g / cm ³ , both inlets from the tank (1). ) for pre-treatment of water and sludge storage and from the purification tank (3) are located in the upper part of the biological filtration stage (9), which is connected downstream to the biological stage (2) and protrudes above the water level, from the bottom of the biological stage (2) to the water level. A small-capacity biological treatment device according to claim 1, characterized in that the density of the culture bodies (5) is greater than 1.0 g / cm ³ and preferably is 1.1 g / cm ³ , both inlets from the tank. (1) for pre-treatment of water and sludge storage and from the purification tank (3) are located at the bottom of the biological filtration stage (9) which is closed down against the biological stage (2) and ends up at the water level; (8) passes from the bottom of the biological stage (2) to above the water level.