RU2531173C2 - Method and plant for deep purification and decontamination of effluents - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to treatment of effluents. Initial effluent flows via pipe 1 into primary settler 2 to be clarified. From said settler 2, water is fed to aeration tank 3 composed by intermediate settler with activated sludge for deep purification of water from contaminants. Then, effluent flows through thin-bed bio-filter 4 with biofilm arranged at its walls to add to filtration of effluent. From bio-filter 4, it flows into secondary settler 5 to settle activated sludge and suspended particles. This sediment is fed back into aeration tank 3 via pipe 10. Note here that this sediment is subjected to treatment by constant electric field of intensity of 2 kV/m. Moreover, it is treated by plates 11 supplied by constant voltage source 12. From settler 5, effluent flows to filter 6 for final removal of suspended particles. Cleaned and decontaminated effluent in discharge pipe 7 is subjected to treatment by constant electric field of intensity of 2 kV/m. Moreover, it is treated by plates 8 supplied by constant voltage source 9. Excess activated sludge from secondary settler 5 and primary settler 2 sediment are removed from the plant via pipe 13.

EFFECT: high-intensity treatment, lower power input, decreased area of treatment plants.

7 cl, 1 dwg, 2 ex

Description

The group of inventions relates to a method and installation for deep cleaning and disinfection of household and wastewater composition close to them.

A known method of purification and disinfection of wastewater, based on the impact on the water of a constant electric field with a strength of 4-20 kV / m The field is created by a pair of electrodes isolated from water (Patent RU 2288893). However, the lower limit of the electric field strength of 4 kV / m is quite high, which requires a voltage transformer.

An additional drawback is the insufficient degree of purification for organic compounds - BOD full is only 20-30% of the initial water pollution instead of the required 90% or more.

The closest technical solution is the "Method of deep biochemical wastewater treatment and installation for its implementation" (Patent No. 2060967).

It consists in the fact that wastewater treatment includes primary sedimentation, aeration, secondary sedimentation and filtration, before primary sedimentation, the wastewater is treated with ozone in an amount of 6.0-60.0 mg / l, and after secondary sedimentation, water is also treated with ozone in an amount 2.0-20.0 mg / l.

However, the energy consumption of the ozonizer is 30-40 kWh per 1 kg of ozone. So, with a consumption of 30 kWh per 1 kg of ozone:

- at a wastewater flow rate of 100 m ³ / day, the total energy consumption will be: 24-240 kW * h / day,

- at a wastewater flow rate of 1000 m ³ / day, the cost of electricity will be: 240-2400 kW * h / day.

This leads to significant energy costs for wastewater treatment.

The technical result of the group of inventions is the intensification of the cleaning process while reducing energy costs when creating an installation for deep biochemical treatment of various composition and amount of wastewater, inexpensive and time-consuming to operate, as well as reduce the volume and area occupied by the treatment plant.

To achieve a technical result, a method of deep biochemical wastewater treatment is used, including primary sedimentation, aeration in the aeration tank, additional treatment in a thin-layer biofilter, removal of activated sludge entering the secondary sump from the aeration tank, additional water treatment from suspended particles in the filter and the release of purified water. At the same time, at the exit of pure water from the filter, it is treated with a constant electric field with a voltage of 2 kV / m or more.

In addition, the return activated sludge from the secondary sump to the aeration tank is also treated with a constant electric field with a strength of 2 kV / m or more.

The method and installation allow for deep biochemical treatment of wastewater, ensuring their disinfection with minimal energy and a significant reduction in the volume of the aeration tank compared to its standard volumes.

We experimentally established that when water is treated with a constant electric field of 2 kV / m or more, water is disinfected by an index of more than 99%.

In addition, the treatment of water containing activated sludge increases the rate of its endogenous respiration and the specific rate of oxidation of organic compounds

$$p=\frac{BP\mathrm{TO}P\mathrm{about}ln}{g*h\mathrm{but}\mathrm{from}}$$

not less than 25%, which has a positive effect on reducing the volume of the aeration tank.

According to SNiP 2.04.03-85, the aeration time in the aeration tank tatm is determined by the formula:

$$\begin{array}{l}tatm=\frac{{}_{(Len\text{Lex})}}{ai(l-s)p},\\ gde\end{array}$$

Len - BOD full of water entering the aeration tank, in mg / l,

Lex - BOD full of purified water, mg / l,

a _i - the dose of sludge, g / l,

s is the ash content of sludge,

p - is determined by the formula (49).

From formula (1) it follows that an increase in p by 25% leads to a decrease in aeration time by 20% and, therefore, under standard conditions, to a decrease in the volume of the aeration tank by 20%. Because the volume of the aeration tank is equal to the product of tatm by the average water consumption of 1 hour.

Installation for deep biochemical wastewater treatment, when implementing the proposed method in it, works as follows.

The group of inventions is illustrated by the installation scheme for deep cleaning and disinfection of wastewater.

The initial wastewater through pipeline 1 enters the primary sump 2, where it is clarified, and due to this, BODfill is reduced. From the primary sump 2, water enters the aeration tank 3, which is made in the form of an intermediate sump with activated sludge for deep purification of water from pollution. Next, the wastewater passes through a thin-layer block 4 of the biofilter, on the walls of which there is a biofilm that further purifies the wastewater. From the thin-layer block 4, the wastewater enters the secondary sump 5. Here, at the bottom of the secondary sump 5, activated sludge and suspended particles settle. This sediment is returned to the aeration tank 3 through a pipe 10, and it is subjected to a constant electric field of 2 kV / m or more using plates 11 fed by a constant voltage source 12. Due to this, the specific rate of oxidation of organic compounds by activated sludge increases by at least than 25%.

From the secondary sump 5, the wastewater enters the filter 6, where it is finally purified from suspended particles.

Then, the purified and disinfected wastewater in the pipeline 7 for the release of purified water is subjected to treatment with a constant electric field with a voltage of 2 kV / m or more using plates 8 connected to a constant voltage source 9. As a result of this, disinfection of wastewater treated according to the index is more than 99%. Excess activated sludge from the secondary sump and sludge from the primary sump are removed from the installation through pipeline 13.

The size of the plates 8 and 11 is determined as follows. The width across the wastewater stream is not less than the outer diameter of the round pipe or not less than the maximum distance between the outer walls of the rectangular pipe. The length of 1 plates 8 and 11 along the stream is determined by the formula

1 = 0.02v,

where v is the flow rate of wastewater. The length is not less than the distance between the plates. As a material for plates, any conductor (aluminum, iron, etc.) can be used. As a material for pipelines, both conductive and dielectrics can be used (steel, cast iron, plastic, etc.).

To power the plates that create a constant electric field in the wastewater stream and the presence of an alternating voltage in the installation? a half-wave or half-wave rectifier is used, at the output of which there is a capacitor with a capacity of 0.1-0.01 μF and connected in parallel to plates located parallel to each other on opposite sides of the pipeline.

If the diameter of the pipeline is such that the distance between the plates creates a constant electric field strength of less than 2 kV / m in the wastewater, then at the place of treatment with an electric field, a large-diameter pipeline is replaced by two or more pipelines of a smaller diameter, or a rectangular pipeline providing a distance between the plates, at which the intensity of the constant electric field in wastewater is 2 kV / m or more.

The cost of electric energy to create a constant electric field plates 8,11 are determined as follows. The current through the plates is 0, because they are isolated from each other. However, reverse current occurs in semiconductors. So, according to Halperin M.V. “Electronic equipment”, for example, the 2D-215 diode, in the voltage range 200–600 V, has a reverse current value of 0.05 mA. From this it follows that at an alternating voltage of 220V, power losses due to reverse current will amount to 0.011 W. There is no direct current, because at the output of the rectifier is a capacitor with a capacity of 0.1-0.01 μF.

Electricity consumed per day will amount to 0.95 kWh for one place of wastewater treatment by a constant electric field with a voltage of 2 kV / m or more. For two treatment sites (return activated sludge and at the outlet of the installation), these costs will amount to 1.9 kWh per day. These energy costs are independent of the amount of waste water flow through the installation and significantly lower than the energy costs in a similar installation (Patent No. 2060967).

Thus, using an alternating voltage of 220V and using the above-described power sources, it is always possible to create a constant electric field of 2 kV / m or more.

Example 1. The consumption of waste water 100 m ³ / day, i.e. 1.16 * 10 ^-3 m ³ / s. BOD _full ⁼ 150 mg / l at the entrance to the aeration tank, and at its exit 6 mg / l. The average content of activated sludge 4 g / l. For domestic wastewater according to SNiP 2.04.03-85, the aeration time is 4.06 hours. The volume of the aeration tank is 16.92 m ³ .

As a result of processing the return activated sludge from the secondary sump into the aeration tank by a constant electric field, the volume of the aeration tank is reduced by 20%, i.e. by 3.38 m ³ and amounts to 13.54 m

The inner diameter of the pipe for pumping settled sludge in the secondary sump into the aeration tank is 20 mm. The distance between the plates is 40 mm. The constant electric field in the wastewater after the rectifier from an alternating voltage of 220 V is 7.8 kV / m.

At the outlet of the treated wastewater from the filter, the inner diameter of the pipe is 60 mm. The distance between the plates is 80 mm. The width of the plates is 70 mm, the length along the stream is 80 mm. The constant electric field in water is 3.9 kV / m.

At the outlet of the installation, the characteristics of the disinfected wastewater: BODful = 3 mg / L, C _pl = 2 mg / L, total nitrogen 7 mg / L, ammonium nitrogen 0.3 mg / L, phosphates 0.6 mg / L. The cost of the electric treatment of water is 1.9 kWh per day.

Example 2. The flow of wastewater 1000 m ³ / day ie 1.16 10 " ² m ³ / s. At the entrance to the aerotank the BOD is _full ⁼ 160 mg / l, at the exit is 6 mg / l. The average content of activated sludge in the aeration tank is 4 g / l. For domestic wastewater according to SNiP 2.04.03-85 time aeration is 4.37 hours. The volume of the aeration tank is 182.2 m ^3. As a result of treating the return sludge with a constant electric field, the volume of the aeration tank is reduced by 20%, that is, 36.4 m ³ and amounts to 145.8 m. activated sludge from the secondary sump 65 mm. The distance between the plates 85 mm. Field of the waste water after the rectifier from AC voltage 220v is 3.6 kV / m.

At the outlet of the treated wastewater from the filter, in the place where it was treated with a constant electric field, a rectangular pipeline with an internal height of 100 mm and a width of 860 mm is located. The distance between the plates is 115 mm. The width of the plates is 870 mm, the length along the stream is 115 mm. The constant electric field in water is 2.7 kV / m. At the outlet from the installation characteristics disinfected wastewater: BOD = 3 mg / L, C = _weighi 3mg / liter, total nitrogen of 8 mg / liter, ammonia nitrogen 0.3 mg / l Phosphates 0.5 mg / l.

The above examples allow us to conclude that the proposed method and installation for deep cleaning and disinfection of wastewater is highly effective. The method and installation can accelerate the biological process in the aeration tank, reduce its size and metal consumption, to obtain purified and disinfected water at the outlet of the installation.

Claims (7)

1. A method of deep cleaning and disinfection of wastewater, including primary sedimentation, aeration in an aeration tank, additional cleaning in a thin-layer biofilter, secondary sedimentation in a secondary sump, cleaning of suspended particles in the filter, and also returning activated sludge settled in the secondary sump to the aeration tank and removing excess activated sludge is carried out through an appropriate pipeline, characterized in that at the outlet of the biofilter, the wastewater is treated with a constant electric field with a voltage awn from 2 kV / m or more, the return activated sludge from the secondary settling tank in the aeration tank is processed with a constant electric field intensity of 2 kV / m or more. 2. The method according to claim 1, characterized in that to create a constant electric field in the wastewater, plates of conductive material are used, isolated from each other and located parallel to each other on opposite sides of the pipeline. 3. The method according to claim 2, characterized in that the plates are powered from an alternating voltage network, which is converted to constant by means of half-wave or half-wave rectifiers, at the output of which a capacitor of 0.1-0.01 μF is connected in parallel to the plates. 4. The method according to claim 2, characterized in that the size of the plates providing the wastewater is treated with a constant electric field is established: the width across the stream is not less than the maximum external size of the pipeline, and the length along the stream is determined by the formula - 1 = 0.02 v, but no less than the distance between the plates. 5. Installation for deep cleaning and disinfection of wastewater, including a primary sump, aeration tank, a secondary sump, a thin-layer biofilter located between the primary and secondary sumps, a pipeline for supplying initial waste water to the primary sump, a pipeline for discharging purified water from the secondary sump, a sludge removal pipeline from a secondary settling tank and an activated sludge recirculation pipeline between the primary and secondary settling tanks, characterized in that a clarified water discharge pipe is installed The first plates are connected to the first constant voltage source. 6. Installation according to claim 5, characterized in that the second plate connected to the second constant voltage source is installed on the activated sludge recirculation pipeline. 7. Installation according to claim 6, characterized in that a filter is installed in front of the purified water outlet pipe.