SK162098A3 - Method and device for the two-stage biological purification of sewage - Google Patents

Abstract

In the present invention there is disclosed two-stage biological sewage treatment process using fluidized activated sludge. The process is characterized in that sewage is supplied into an equalizing tank and during filling a reactor, sewage is subsequently pumped by a crude water pump into a reactor for additional treatment. During filling from the minimum to the maximum level, the reactor is aerated, whereby the equalizing tank is aerated during the emptying phase of the reactor from the maximum to the minimum level. Claimed is also a two-stage biological sewage treatment plant using fluidized activated sludge wherein the plant comprises an equalizing tank /1/ with sewage inlet /3/ and an excessive sludge pump /12/, a maximum and minimum level float switch /26/, a purified water pump /13/, an aeration device /11/, a float change-over switch /7/ maintaining a hold mode in the tank /1/ for blocking the purified water pump /13/, wherein in the reactor /2/ there is situated at the level between the maximum and minimum levels a float change-over switch /4/ of the purified water pump /13/.

Description

Technical field

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stage biological treatment of waste water using an activated sludge activated sludge system and an apparatus for carrying out the method, particularly suitable for small domestic treatment plants.

BACKGROUND OF THE INVENTION

Biological wastewater treatment uses activated sludge, a mixture of different bacteria and microorganisms. This sludge needs for its life organic substances in the waste water, which it decomposes and thus purifies the waste water. The activation process is only possible with continuous oxygenation, which is usually solved by blowing air into the activation tank.

Wastewater treatment uses both microorganisms firmly adhered to the substrate in the form of various biofilter and bioreactor systems that are wetted with waste water, as well as float sludge activation systems where sludge flakes are mixed with waste water and air.

Hitherto known wastewater treatment plants with suspended sludge can be divided into systems with continuous waste water flow through the activation tank and into systems with discontinuous flow.

In the case of a continuous purification system, the waste water after the coarse treatment is fed to the activation tank and after a technologically necessary time for water purification, the purified water is discharged together with the activated sludge into a separate settling tank. In this tank the sludge settles and clean water is discharged to the drain.

In the case of discontinuous flow systems, the waste water is fed to the activation tank directly or after being pumped from the buffer tank after rough cleaning. After purification of the water, the activation process is interrupted, i.e. the aeration and eventual mixing of the water in the activation tank is stopped, and after settling the sludge, the purified water is pumped or drained gravitationally to waste. The activation tank is then refilled and the cycle is repeated. Compared to continuous cleaning, the settling tank is eliminated and the activation tank (SBR) is inflated cyclically.

A disadvantage of the above-described activation wastewater treatment systems is that they are difficult to utilize to purify the smaller volumes of wastewater produced, e.g. in family houses, in smaller production plants, etc., they can be used for small domestic sewage treatment plants due to high demands on the operation control of these systems.

In the case of continuous-flow activation plants, the sludge from the sedimentation tank must be permanently pumped back to the wastewater flow to the activation tank. If the sludge concentration in this tank rises above the permissible value, the excess sludge must be drained from the treatment plant. Regular measurements of sludge concentration in the activation tank and sludge pumping require qualified personnel. In addition, the activation tank would be unevenly loaded at the sewage flow. This would result in a deterioration of the outflow water quality or, in the case of the desired water quality, the activation and settling tank would have to be oversized.

Hitherto known small continuous sludge treatment plants with suspended activated sludge are, due to the accumulating sludge in the activation tank, designed either to a large sludge density, which is necessary to maintain in an energy-intensive hovering without interruption of the treatment plant up to 200 days until sludge. provides sludge activation tank. Both of these systems cannot operate for a long time without the inflow of sewage, because after the consumption of organic substances in the activation tank, the sludge is gradually autolysed and disappears from activation. This significantly disrupts the operation of the treatment plant. Activation plants with an intermittent activation tank flow rate (SBR) are characterized by a relatively complex control system with several pumps and are therefore too expensive for small wastewater sources.

SUMMARY OF THE INVENTION

The above-mentioned deficiencies are eliminated by the method of two-stage waste water treatment with biological activated sludge. The essence of the solution according to the invention consists in the fact that the wastewater is introduced into the first activation stage, which at the same time has the function of a buffer tank and a sludge tank, and which is in the phase of slow filling II. The activation stage, which is formed by the reactor, is then pumped through the raw water pump for purification. During cleaning, the reactor is aerated from the minimum to maximum level during the slow-fill phase, while the buffer tank is aerated from the maximum level to the minimum level during the reactor emptying phase. The reactor is emptied immediately after the reactor is filled. The time required to separate the sludge from the purified water and settle on the bottom during the reactor emptying phase is determined by the time of transfer of excess sludge and part of the purified water from the reactor to the buffer tank at which the maximum level in the reactor drops to the level required to start the clean water pump. In the event that the water level in the buffer tank drops to a minimum level, the pumping of pure water into the drain is blocked and the reactor charge volume between the maximum and minimum levels is pumped through the excess sludge pump to the buffer tank. If the water level in the buffer tank rises to the specified level, the pumping of clean water into the drain is unblocked.

This two-stage discontinuous activation sewage treatment plant consists of a buffer tank with a waste water flow and a raw water pump and a reactor with an excess sludge pump, a float switch for maximum and minimum levels, a clean water pump and an aeration device. In addition, an aeration device and a float switch of the holding mode for blocking the clean water trap are located in the buffer tank. The float switch of the clean water pump is located in the reactor between the maximum and minimum level. Typically, the system further includes a central compressor, electrical switchboard, air distribution, calibrated air distribution nozzles for each size plant and a power regulator that is fitted to the plant's electrical connections. A similar variant of the solution is a system where two separate compressors are used instead of one compressor and two pieces of solenoid valves.

The above-described treatment plant takes advantage of the discontinuous activation system (SBR), which eliminates the operational and design-intensive settling tank, while simplifying the management of the system as much as possible. Because the entire system is controlled only by level sensing, usually only floats, and requires no electrical timers, control is very simple and reliable, making it possible to use the SBR system for the smallest pollution sources. At the same time, the efficiency of the treatment is considerably increased, since the blower output is fully utilized during the sedimentation and emptying times of the reactor for aeration of the 1st activation stage, where a considerable degree of wastewater pre-treatment and aerobic stabilization of excess sludge occur.

The most advantageous application of this system is the reconstruction of already built cesspools and septic tanks to waste water treatment plants. In this case, the existing cesspool has the function of a buffer tank and a sludge tank, and only the reactor with aeration and control system is newly inserted into the cesspool, thus creating a complete domestic treatment plant.

These are obviously the smallest treatment plants that operate through controlled denitrification. Nitrification, i.e., the biological oxidation of ammonia to nitrates, is simultaneously carried out in the reactor during filling and biological purification. Upon re-pumping the purified water into a buffer tank with an anoxic environment, nitrogen gas is biologically released from the purified water. The mixture of raw and purified water which is subsequently pumped into the reactor already contains substantially less nitrogen. The efficiency of denitrification is given by the ratio of purified water which is pumped from the reactor into a buffer tank to the volume of water which is pumped to the effluent in one cycle. This ratio is easily determined by adjusting the start level of the clean water pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached drawing shows one possible embodiment of a two-stage activation treatment plant according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The activation treatment plant according to the figure consists of two waterproof separate activation tanks. I. activation stage consists of buffer tank i, usually existing cesspool and II. Reactor stage 2. The buffer tank 1 serves to accumulate and equalize the uneven inflow of sewage while at the same time coarse impurities are trapped and excess sludge is accumulated from the reactor 2. Thus, a mixture of primary and excess activated sludge with a mixture of raw and purified waste water is stored and intermittently aerated. In the buffer tank 1 there is an aeration element 11, a raw water air pump 9, a float switch 7 of the holding mode and a coarse dirt filter 10 with aeration. The reactor 2 comprises the excess sludge air pump 12, the clean water air or electric pump 13, the aeration element 11, the maximum and minimum float switch 26 in the reactor 2 and the clean water float switch 4.

The waste water is fed to the buffer tank 1 and from there it is pumped slowly through the coarse dirt filter 10 through the raw water air pump 9 to the reactor 2, where it is aerated and purified during the filling of the reactor 2. Filling of the reactor 2 proceeds from a minimum level of 14 to a maximum level of 15. The filling range of the reactor 2 is adjusted to between 15% and 60% of the volume of the reactor 2 and the filling then usually takes from one to five hours.

After the reactor 2 has been filled to the maximum level 15, the float switch 22 closes the charging valve 19 and at the same time opens the discharge valve 2 of the reactor 2. This results in the emptying phase of the reactor 2 with simultaneous aeration of the buffer tank 1. . Throughout this phase, an excess sludge air pump 12 is operated, which lowers the water level in the reactor 2 from the maximum level 15 to the start level 16 of the clean water pump 13, which unlocks the clean water pump solenoid 21, thereby introducing the clean water pump 13. Into service. This time interval required to separate the sludge from the purified water is determined by the pump output of the excess sludge 12 and is usually from 30 to 90 minutes. When the clean water pump 13 is switched on, the reactor is quickly pumped to a minimum level of 14 to terminate the emptying phase of the reactor 2 associated with the aeration of the buffer tank 1 and at the same time starting the next filling phase of the reactor 2. This operation is repeated cyclically.

The inlet to the excess sludge pump 12 is at the desired sludge level 17 in the reactor 2 after settling. This means that the optimum amount of activated sludge in reactor 2 is automatically maintained for each cycle.

If there is insufficient sewage flow into the sewage plant, the level in the buffer tank 1 will drop to the set minimum level 5, with the float switch 7 blocking the electrovalve 21 of the clean water pump 13 even after the level in reactor 2 has fallen to start level 16 of the clean pump 13. As a result, the emptying phase of the reactor 2 associated with the aeration of the buffer tank 1 lasts as long as the entire volume of the reactor 2 from the maximum level 15 to the minimum level 14 is slowly pumped through the excess sludge pump 12 to the buffer tank. cleaning. As long as the electricity is supplied to the treatment plant without interruption, the compressor operates 24 hours a day with alternating aeration of the buffer tank 1 and the reactor 2 and thus the treatment plant operates at full capacity. If the power supply interruption 24 is set on the power regulator 24, this will reduce the total running time of the compressor 25 and thus the operation of the treatment plant. This makes it very simple and efficient to control the plant's performance while saving electricity according to the plant's actual load.

The same way the system works when using two separate compressors. One is then in operation for the filling phase of reactor 2 and the other for the phase of its emptying. Then, instead of opening and closing the solenoid valves 19 and 20, the maximum and minimum level level switch 26 then alternately triggers one of the two compressors.

Claims (4)

PATENT CLAIMS 1. Method of two-stage waste water treatment with biologically activated suspended sludge, in which waste water is fed into the buffer tank and subsequently pumped through the raw water pump into the reactor for purification, characterized in that the reactor is aerated in the filling phase from the minimum to the maximum level, the buffer tank being aerated during the reactor emptying phase from the maximum to the minimum level. Wastewater treatment method according to claim 1, characterized in that the time required to separate the sludge from the treated water and to settle at the bottom in the reactor emptying phase is determined by the time of pumping the excess sludge and part of the purified water from the reactor into the buffer tank. by which the maximum level in the reactor drops to the starting level of the clean water pump. Wastewater treatment method according to claims 1 and 2, characterized in that, when the water level in the buffer tank drops to a minimum level, the pumping of clean water into the drain is blocked and the reactor filling volume between the maximum and minimum levels is pumped through an excess sludge pump. If the water level in the buffer tank rises to the specified level, the pumping of clean water into the drain is unblocked. 4. Biological two-stage activated sludge activated sludge sewage treatment plant with suspended activated sludge, consisting of a buffer tank with a sewage inlet and a raw water pump and a reactor with excess sludge pump, maximum and minimum float switch, clean water pump and aeration device, that the buffer tank (1) is further provided with an aeration device (11) and a float switch (7) of a maintenance mode for blocking the clean water pump (13), wherein a float switch is arranged in the reactor (2) between the maximum and minimum levels. (4) clean water pumps (13).