KR100304404B1 - Dense wastewater treatment method by fixed biofilm and continuous backwash filtration - Google Patents

Abstract

The present invention enables the removal of nutrients such as nitrogen along with organic matter, suspended solids, etc. through the combination of fixed biofilm and continuous backwash filtration method, and reduces the scale of sewage water treatment process by excluding secondary sedimentation tank and extra filtration tank. It is intended to pursue various economic benefits, such as cost reduction, by providing a compact high-level wastewater treatment method that can solve the site securing problem of the treatment plant.

The present invention provides a process for converting nitrates into nitrogen gas and removing organic substances by denitrification in an anoxic tank (1, 2), in which sewage water introduced into a fixed biofilm reactor (A) filled with a carrier for biofilm attachment is fixed; Floatability in the process of removing the remaining organic substances from the denitrification process in the aerobic tanks (3,4) and converting ammonia nitrogen to nitrate, and in the process through the anoxic tanks (1,2) and the aerobic tanks (3,4). The solid material is adsorbed and removed into the biofilm, and the remaining solids and nitrates of the treated water passing through the fixed biofilm reaction tank (A) are removed from the continuous backwash filtration tank (5) to discharge the removed solids through the solid discharge pipe (7). The final treated effluent is discharged through the filtered water discharge pipe (6),

It is important to note that some of the effluents are returned to the anoxic tanks (1, 2) for the removal of nitrates.

Description

Dense wastewater treatment method by fixed biofilm and continuous backwash filtration

The present invention relates to a novel method of dense advanced sewage treatment using a fixed biofilm method and a continuous backwash filtration method.

As the conventional wastewater treatment method, the activated sludge method is generally used. This method uses floating microorganisms, which adversely affects the microorganisms in the presence of fluctuations in loads of pollutants and influx of toxic substances in the wastewater, thereby properly operating the reactor. The disadvantage is that it is not easy to manage.

In addition, secondary sedimentation tanks are necessary for maintaining sufficient concentration of microorganisms in the reaction tank and separating treated water and sludge. At this time, the problem of deterioration of treated water quality may occur because solid-liquid separation is not performed due to problems such as swelling. do.

In addition, 0.5 kg of microbial mass is generally generated per 1 kg of BOD (biochemical oxygen demand) to be removed, and surplus biomass other than the appropriate amount of microorganisms required for stable reactor operation must be continuously discarded in the reactor.

In contrast, the fixed biofilm method, which has recently been spotlighted as a new wastewater treatment process, can maintain a high concentration of microorganisms in a unit reaction tank and has a strong coping capacity against load shock and toxic substances in wastewater.

In addition, as the microorganisms are attached to the carrier and grow, the residence time in the reaction vessel becomes considerably longer, so that the amount of excess sludge generated by endogenous breathing is considerably reduced to about 1/4 of the activated sludge method.

In addition, since the particulate solid material is substantially removed through adsorption in a biofilm reactor without undergoing a process such as solid-liquid separation in the secondary settling tank, it may provide a condition to exclude the secondary settling tank.

In addition, since the microorganism is fixed to the carrier, the sludge required for maintaining the concentration of the microorganism in the reaction tank is not required.

In addition, nutrients such as nitrogen can be removed by introducing an aerobic and anoxic tanks through proper fractionation of biofilm reactors.

Most of the biofilm methods widely used in the past have been used in the form of a biofilter, which requires the periodic backwashing process due to the pressure loss caused by excess biofilm during operation and channeling. It has the same limitation as the occurrence of.

On the contrary, the method adopted in the present invention is not a filtration type, but a horizontal type of reaction tank, which can avoid problems such as pressure loss, and has an advantage that it can be applied to an existing wastewater treatment plant simply by expanding a facility.

Conventional filtration tanks commonly used as post-treatment processes require backwashing as the pressure loss in the bed increases after a certain period of time (usually 24 hours).

In this case, sewage treatment plants usually have several sets of filtration tanks for alternating filtration and operate alternately.

Such extra filtration tanks are an obstacle to the compact construction of the equipment scale, and it is difficult to promote the continuity of the filtration work because the treatment process must be temporarily suspended in order to operate alternately.

In the continuous backwash filtration process which is part of the present invention, the limitations of this conventional filtration tank are overcome.

As the backwashing process for continuity of filtration takes place simultaneously with filtration, the bed always remains in its initial operating state.

That is, the filtration process can be maintained continuously.

The use of such a continuous backwash filtration tank does not need to have a spare filtration tank, which can be said to have a large cost reduction effect due to facility exclusion.

As the social expectations for the water environment have increased, it has become difficult to meet the existing sewage treatment methods.

In addition to organic and suspended solids, which are the main pollutants of the past, the removal of nutrients such as nitrogen is urgently required.

In addition, the problem of securing land in sewage treatment plants is becoming a strong motivation to reduce the size of sewage treatment processes.

At this point, the various characteristics proposed by the present invention have sufficient advantages as an alternative to the low cost, high efficiency wastewater treatment method.

Accordingly, the present invention enables the removal of nutrients, such as nitrogen, together with organic matter, suspended solids, and the like through a combination of a fixed biofilm excluding a secondary precipitation tank and a filtration tank and a continuous backwash filtration method, and reduces the scale of the wastewater treatment process. The present invention aims to provide a compact advanced wastewater treatment method that can solve the problem of securing the site of the wastewater treatment plant.

1 is a whole system consisting of a immersion-type fixed biofilm and a continuous backwash filtration tank showing an embodiment of the present invention

2 is an internal structure diagram of a continuous backwash filtration tank

☞ Explanation of symbols used in the main part of the drawing ☜

A; fixed biofilm reactor

1,2; anaerobic bath 3,4; aerobic bath

5; Continuous backwash filtration tank 6; Filtrate drainage pipe

7; solid discharge pipe 8; return pipe

9; Stirrer 10; Blower

11; Air compressor 12; Raw water storage tank

51; inlet pipe 52,52 '; inlet distribution hood

53; Filtrate 54; Weir

55; air supply unit 56; air supply pipe

57; sand washer 58; back wash drain Weir

1 is a view showing the entire system consisting of a immersion-type fixed biofilm and a continuous backwash filtration tank showing an embodiment of the present invention,

The fixed biofilm reactor A is filled with a carrier for biofilm adhesion into the stationary phase. The carrier to be applied may be used in various kinds.

Wastewater flowing into the fixed biofilm reactor A from the raw water storage tank 12 is converted to nitrogen gas at the same time as the nitrates returned to the return pipe 8 by denitrification in anoxic tanks 1 and 2 of FIG.

The organic matter remaining in the denitrification process is removed from the aerobic tanks 3 and 4.

In addition, in the aerobic tanks 3 and 4, ammonia nitrogen is converted into nitrates.

In the process of passing through the fixed biofilm reactor A, the solids contained in the wastewater are mostly adsorbed and removed from the anoxic tanks 1 and 2 and the aerobic tanks 3 and 4.

The treated water passing through the fixed biofilm reactor A removes most of the organics and solids, leaving only the remaining solids and nitrates, which are then removed through a continuous backwash filtration tank 5.

The solids removed in the continuous backwash filtration tank 5 are discharged through the solid discharge pipe 7 and the discharged treated water is discharged through the filtered water discharge pipe 6.

At this time, some of the effluent is sent to anoxic tanks 1 and 2 again for the removal of nitrates.

Meanwhile, the continuous backwash filtration tank 5 is provided with a return tube 8 for returning nitrates to the anoxic tanks 1 and 2 and an air compressor 11 for blowing air for backwashing, and the anoxic tanks 1 and 2 are completely equipped with anoxic tanks 1 and 2. A mixer 9 and an aerobic tank 3 and 4 for achieving a mixed state are provided with a blower 10 for supplying oxygen, respectively.

The present invention is characterized by providing a compact advanced wastewater treatment method using the fixed biofilm reactor A and the continuous backwash filtration tank 5 described later.

Figure 2 shows the internal structure of the continuous backwash filtration tank,

The treated water having passed through the fixed biofilm reactor A is introduced into the inlet pipe 51 and flows into the inlet water distribution hood 52, 52 'from inside the filter sand 53.

The influent distribution hood 52, 52 'is inverted V to distribute the influent evenly into the filtrate 53 and the solids contained in the influent are filtered out by the filtrate 53.

The filtered filtrate is discharged to the final effluent through the effluent weir 54 through the filtrate discharge pipe 6 of FIG.

Some of the effluent is returned to the anaerobic tank 1 of the fixed biofilm reactor A through the return tube 8 of FIG. 1 connected to the filtered water discharge tube 6 for the denitrification process, and the sand filter media (53) filtering the solids of the influent is gradually lowered. It flows up through the air floater 55 at the bottom of the filtration tank 5.

When air is supplied into the air buoy 55 through the air supply pipe 56 connected to the air compressor 11 of FIG. 1, the filtration yarn 53 which collects the solids at the bottom of the continuous backwash filtration tank 5 floats upwards. As a result, the solid matter attached to the sand particles falls off and is washed.

In the sand washer 57, the sand particles flowing from the upper portion of the air floater 55 flows down due to the specific gravity, passes through a zigzag passage formed at the bottom, and the remaining solids are shaken off and fall back to the surface layer of the filter sand 53.

Solids separated from the sand particles are discharged through backwash effluent 58.

Since the level of the effluent ware 54 is kept above the level of the backwash effluent ware 58, the filtered effluent always flows over the sand washer 57 and prevents recontamination of the filtered water by solids separated from the sand particles.

Hereinafter, the present invention will be described in more detail through one embodiment.

Example

The fixed biofilm reactor A was operated for 180 days with a hydraulic residence time of 8 hours to obtain the following results.

The filling rate was 20% based on the volume of the reactor using a commercially available carrier.

When the average SS concentration of raw water was 82mg / l, the effluent quality of the fixed biofilm was 30mg / l.

Operation of the average concentration of the raw water COD 285mg / l and a mean volume load 0.85kgCOD / m ³ under the conditions of organic removal efficiency .d 77%, the removal rate was obtained 0.7kgCOD / m ³ .d.

At this time, the removal efficiency remained stable at 80% when the organic load ranged from 0.5kgCOD / m ³ .d to 1.4kgCOD / m ³ .d.

The average NH ₄ -N 72mg / l of raw water showed more than 91% of the nitrification rate in the fixed biofilm reactor A and the discharge quality was less than 5mg / l.

The average nitrification rate was 0.2 kg NH ₄ -N / m ³ .d.

Jilsanhwayul as the ammonium nitrogen load amount to 0.13~0.32kgNH ₄ -N / m ³ .d exhibited ^{_{0.12~ 0.29kgNH 4 -N / m 3 .d}} .

The total nitrogen removal efficiency in the fixed biofilm reactor was 70% during the operation period and the removal rate was 0.15kgN / m ³ .d.

When the continuous backwash filtration tank was operated at various filtration rates, the following results were obtained.

Filtration quality of the treated water is to give the quality of the treated water in the 9mg / l and when 2NTU 30L / m ² .min an average suspended solids and turbidity of the raw water 48mg / l, in 23NTU days.

Filtration to give the quality of the treated water quality of the treated water is of 19mg / l and when 3NTU 50L / m ² .min an average suspended solids and turbidity of the raw water 47mg / l, in 9NTU days.

Filtration to give the quality of the treated water quality of the treated water is of 18mg / l and when 4NTU 70L / m ² .min an average suspended solids and turbidity of the raw water 42mg / l, in 10NTU days.

Filtration to give the quality of the treated water quality of the treated water is of 27mg / l and when 8NTU 100L / m ² .min an average suspended solids and turbidity of the raw water 53mg / l, in 16NTU days.

Table 1 below shows the removal efficiency at each filtration rate.

Water factor Filtration rate (L / m ² .min) 30 50 70 100 Floating Solids Removal Efficiency (%) 79 59 58 47 Turbidity Removal Efficiency (%) 74 60 62 54

As described above, the present invention uses the fixed biofilm method. First, it is possible to handle high loads by maintaining a high concentration of microorganisms in the reaction tank, and secondly, to treat the high load of the biofilm and to remove the excess sludge. The low concentration of solids provides a condition for excluding the secondary sedimentation tank and filtering the treated water directly. Third, microorganisms are fixed to the carrier in the reaction tank to maintain the proper concentration of microorganisms in the reactor as in activated sludge method. It is possible to reduce the related equipment because there is no need for sludge return, and fourthly, since denitrification is performed by internal circulation in the reactor itself, a separate denitrification tank is not necessary. and,

In the continuous backwash filtration tank 5, the filtration and backwashing processes are performed continuously, so it is easy to operate and manage, and economic efficiency can be achieved because no extra filtration tank is required.

The dense advanced sewage treatment method using the fixed biofilm and continuous backwash filtration method of the present invention described above is capable of removing organic substances, suspended solids and nitrogen, but with the elimination of the secondary settling tank and the introduction of the continuous backwash filtration method. Unlike the existing filtration method that requires extra filtration tanks, it is possible to perform sufficient filtration function with only a single filtration tank, which enables advanced treatment of wastewater and compaction of the system. The following advantages and economic effects can be expected in various wastewater treatments.

First, it is possible to equip a system that is stable and highly able to handle load fluctuations at low cost in small residential areas where the amount of wastewater generated that does not require a large-scale wastewater treatment plant facilities is low.

Second, it can be usefully applied to places where the wastewater treatment plant site is narrow or a small wastewater treatment plant construction is required, such as inside a building.

Third, the treated water can be reused as toilet water and cleaning water through the disinfection process, and thus can be widely used as a recycling system for wastewater.

Claims (2)

A process for converting nitrates returned to the return tube 8 to nitrogen gas and removing organic matter by the denitrification reaction in the anoxic tanks 1 and 2, in which the wastewater flowing into the fixed biofilm reactor A, in which the carrier for biofilm attachment is filled into the fixed phase, Removing the remaining organic substances from the denitrification process in aerobic tanks 3 and 4 and converting ammonia nitrogen to nitrates; The process of adsorption and removal of suspended solids into biofilm in the course of anoxic tanks 1,2 and aerobic tanks 3,4, Removing residual solids from the treated water that has passed through the fixed biofilm reactor A in the continuous backwash filtration tank 5, and discharging the removed solids through the solid discharge pipe 7 and discharging the final treated effluent through the filtered water discharge pipe 6, Part of the effluent is a high-density sewage treatment method by a fixed biofilm and continuous backwash filtration method characterized in that the step of returning to the anoxic tank 1, 2 to remove the nitrate. Wastewater flows from the raw water storage tank 12, and the nitrates returned from the return pipe 8 are converted to nitrogen gas by denitrification, and anoxic tanks 1 and 2 are removed to remove organic substances, and the remaining organic substances are removed from the denitrification process. Fixed biofilm reaction tank A consisting of aerobic tanks 3 and 4 for converting and filled with a fixed phase with a carrier for biofilm attachment. 10. A densely packed wastewater treatment system using a fixed biofilm and a continuous backwash filtration method, comprising a continuous backwash filtration tank 5 for removing residual solids from treated water passing through the fixed biofilm reactor A.