CN105236564A - Combined packing for biological aerated filter and application of combined packing - Google Patents

Abstract

The invention discloses combined packing for a biological aerated filter. The combined packing is composed of walnut shells and zeolite in a volume ratio of (2-4) : 1. The invention further discloses an application of the combined packing in the biological aerated filter. The combined packing for the biological aerated filter disclosed by the invention is fast in biofilm culturing speed in a same condition compared with other packing. The walnut shells and the zeolite are combined as the combined packing for the biological aerated filter, and therefore, the porosity, the adsorbability, the ion-exchange property and a relatively strong supporting effect of the zeolite are exerted; and the walnut shells are used as a solid carbon source so that no additional carbon source is needed, and the walnut shells further have a certain framework supporting effect, so that the combined packing is not prone to blockage. In addition, the walnut shells as an agricultural solid waste are wide in source and low in price.

Description

A kind of composite filler of biological aerated filter and its application

technical field

The invention belongs to the technical field of water treatment, and in particular relates to a combined filler for an aerated biological filter, and also relates to the application of the combined filler in an aerated biological filter.

Background technique

In recent years, due to the improvement of human living standards and the excessive use of agricultural chemical fertilizers, a large amount of nitrogen-containing domestic sewage and industrial wastewater have been discharged into water bodies. Nitrogen is the main factor causing eutrophication of water bodies and can be transformed into "three causes" The substance nitrite seriously threatens human health. Therefore, the research and development of economical and efficient wastewater denitrification treatment technology has become the focus and hot spot in the field of water pollution control engineering. Among the many denitrification technologies, the biological aerated filter (BAF) integrates biological oxidation and interception of suspended solids, eliminating the need for subsequent secondary sedimentation tanks, simplifying the treatment process under the premise of ensuring the treatment effect, and occupying an area Small area, high treatment efficiency, good effluent quality, easy automatic control, etc. Especially in recent years, the research on the nitrification and denitrification functions of the reactor has become a hot spot.

As the carrier of microorganisms, the filler is a place for microorganisms to inhabit and reproduce. At the same time, it also plays a role in intercepting suspended matter during operation. It is one of the cores of biological aerated filter treatment technology. Its material composition and surface properties will directly affect The attachment, growth, reproduction and activity of microorganisms on the surface of fillers will affect the performance of microbial film formation and the degradation efficiency of pollutants. Different fillers form different biofilms, and different biofilm states lead to differences in microbial ecology in the system, which will have a great impact on the treatment efficiency of the reactor.

At present, the biological aerated filter fillers that have been studied more mainly include activated carbon, spherical lightweight porous biological ceramsite fillers fired with fly ash and clay as the main raw materials, natural silicate mineral fillers such as zeolite, and fillers made of various fillers. Combination of composite fillers, etc. Activated carbon is used as a filler, which is expensive, and the agitation of the gas and aqueous solution in the activated carbon biological aerated filter makes the activated carbon biological filter effluent color darker, causing the turbidity of the effluent to increase, even greater than the turbidity of the influent water; zeolite as aeration Due to its irregular shape and large water flow resistance, the packing of biological filter is easy to be blocked, and the distribution of water and air is not easy to be uniform. The surface of zeolite has a negative charge, which is not conducive to the growth of microbial film formation when used alone as a biological aerated filter filler; walnut shells as a biological aerated filter filler require a long time to form a film, and due to microbial decomposition, the filler after long-term operation The column collapsed. Therefore, it is necessary to develop inexpensive, widely sourced and efficient biofilter fillers.

Contents of the invention

The object of the present invention is to provide a composite filler for biological aerated filter, the composite filler has fast film formation speed, good denitrification performance under optimal operating process parameters, wide sources and low price.

Another object of the present invention is to provide an application of the above combined filler in a biological aerated filter.

The technical scheme adopted in the present invention is a combined packing of biological aerated filter, which is composed of walnut shell and zeolite, wherein the volume ratio of walnut shell and zeolite is 2-4:1.

The present invention is also characterized in that,

The average particle size of walnut shell and zeolite is 4-6mm.

Another technical solution adopted by the present invention is that the application of the above-mentioned combined filler in the biological aerated filter is specifically implemented according to the following steps

Step 1, static film hanging stage

Mix walnut shells with an average particle size of 4-6mm and zeolite at a volume ratio of 2-4:1 and put them into the biological aerated filter, and inject the activated sludge into the filter for aeration to restore the sludge Activity, the amount of sludge dosage is based on filling the filter tank. After inoculating the sludge, a small amount of water is fed in, and air is introduced for aeration and stirring. Every 24 hours, 1/3 of the upper layer solution in the filter tank is taken out and drained. Supplement the simulated wastewater, monitor the water quality of the reactor effluent regularly every day, that is, monitor pH, DO, COD and NH ₄ ⁺ -N, and observe the growth of microorganisms on the filler under a microscope; enter the continuous culture stage after 7 days;

Step 2, continuous culture phase

Discharge the suspended microorganisms that cannot effectively hang the film, use the simulated wastewater to continuously feed water and air, keep the hydraulic retention time of the biofilter at 12h, keep the dissolved oxygen concentration at 4mg/L during the film hanging period, and the dissolved oxygen concentration meets the requirements Under the premise of reducing the amount of aeration as much as possible, the water quality of the reactor effluent is regularly checked every day, that is, the pH, DO, COD, and NH ₄ ⁺ -N are monitored, and the growth of microorganisms on the filler is observed; if the effluent water quality fluctuates slightly, the COD And the removal rate of NH ₄ ⁺ -N tends to be stable, and it can be observed under the microscope that the effluent contains more bell worms, indicating that after a period of domestication and cultivation, the biofilm has formed and is gradually growing and maturing, with strong load resistance Impact capacity, to determine the success of film hanging;

Step 3, Biological Aerated Filter Operation Phase

After successful film formation, the pH value is 7.5-8.5, the COD concentration of the influent water is 300mg/L, and the NH ₄ ⁺ -N concentration is 30mg/L. , NH ₄ ⁺ -N, NO ₂ ^- -N and NO ₃ ^- -N water quality indicators.

The present invention is also characterized in that,

In step 1, the aeration rate is 9 L/h, and intermittent aeration is adopted, and after 3 hours of aeration, it is left to stand for 1 hour to cultivate microorganisms.

In step 3, the aeration rate is 9-12 L/h, the hydraulic load is 0.03-0.06 m ³ /(m ² ·h), and the air-water ratio is 3-12:1.

The beneficial effect of the present invention is that, compared with other fillers, the combined filler of the biological aerated filter of the present invention has a faster film-forming speed under the same conditions; walnut shells and zeolite are combined as the filler of the biological aerated filter, which can not only exert the zeolite Porosity, adsorption, ion exchange performance and relatively strong support, and walnut shells are used as a solid carbon source without additional carbon sources, walnut shells also have a certain skeleton support, and are not prone to blockage. In addition, as a kind of agricultural solid waste, walnut shell has a wide range of sources and low price.

Description of drawings

Figure 1 is the COD change curve during the film-hanging start-up period;

Figure 2 is the NH4 ⁺ -N change curve during the start-up of film formation;

Figure 3 is the influence curve of the hydraulic load in the operation stage of the biological aerated filter;

Figure 4 is the influence curve of the air-water ratio in the operation stage of the biological aerated filter.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The invention relates to a combined filler for an aerated biological filter, which is composed of walnut shells and zeolite, wherein the volume ratio of the walnut shells to the zeolite is 2-4:1.

The average particle size of walnut shell and zeolite is 4-6mm.

The application of the above-mentioned combined filler in the biological aerated filter is implemented according to the following steps:

Step 1, static film hanging stage

Mix walnut shells with an average particle size of 4-6mm and zeolite at a volume ratio of 2-4:1 and put them into the biological aerated filter, and inject the activated sludge into the filter for aeration to restore the sludge Activity, the amount of sludge dosage is based on filling the filter tank. After inoculating the sludge, a small amount of water is introduced into the water, and air is introduced for aeration and stirring. The aeration rate is 9L/h, and intermittent aeration is used. After 3 hours, let it stand for 1 hour to cultivate microorganisms, so that the microorganisms with good adhesion on the filler can fully grow, adhere and grow on the filler carrier; take out 1/3 of the upper layer solution in the filter every 24 hours, and supplement the simulated wastewater , regularly monitor the water quality of the reactor effluent every day, that is, monitor pH, DO, COD and NH ₄ ⁺ -N, and observe the growth of microorganisms on the filler under a microscope; enter the continuous culture stage after 7 days;

Step 2, continuous culture phase

Discharge the suspended microorganisms that cannot effectively hang the film, use the simulated wastewater to continuously feed water and air, keep the hydraulic retention time of the biofilter at 12h, keep the dissolved oxygen concentration at 4mg/L during the film hanging period, and the dissolved oxygen concentration meets the requirements Under the premise of reducing the amount of aeration as much as possible, this will not only reduce the erosion of the surface of the filter material, but also facilitate the attachment and growth of microorganisms. The water quality of the reactor effluent is regularly checked every day, that is, pH, DO, COD, and NH ₄ ⁺ - N, and observe the growth of microorganisms on the filler; if the effluent water quality fluctuates less, the removal rate of COD and NH ₄ ⁺ -N tends to be stable, and it can be observed under the microscope that the effluent contains more bell worms, indicating that after a period of time After domestication and cultivation, the biofilm has formed and is gradually growing to maturity, and has a strong ability to resist load shocks, which confirms the success of the film formation;

Step 3, Biological Aerated Filter Operation Phase

After successful film formation, the pH value is 7.5-8.5, the influent COD concentration is 300mg/L, the NH ₄ ⁺ -N concentration is 30mg/L, the aeration rate is 9-12L/h, and the hydraulic load is 0.03-0.06m ³ /( m ² h), the gas-water ratio is 3-12:1, and the water quality of the reactor effluent is regularly monitored every day, that is, pH, dissolved oxygen, COD, NH ₄ ⁺ -N, NO ₂ ^- -N and NO ₃ ^- -N water quality indicators.

Example 1

The walnut shell and zeolite are mixed in a volume ratio of 3:1 and applied to the biological aerated filter.

1. The start-up and operation effect of the biological aerated filter with membrane

(1) COD concentration and its removal rate during the start-up of film formation

It can be seen from Figure 1 that the COD removal rate of the biological aerated filter is about 60% at the initial stage of continuous water inflow during the start-up period of the film hanging, and when the continuous reaction reaches the fifth day, the COD removal rate is 61.5% of the previous day Rapidly increased to 90%. When the influent organic matter concentration (COD) was in the range of 218.4mg/L-353.9mg/L, COD maintained a high removal rate (61.5%-94%). It can also be seen that, except for the special circumstances of a few days, the COD removal rate generally increases with time, and in the late start-up period, even if the influent COD concentration fluctuates greatly, it also has a high removal rate. This shows that after a period of domestication and cultivation, the biofilm has formed and is gradually growing and maturing. Moreover, due to the large specific surface area of the biological aerated filter material, the biomass per unit surface area is high, and when the external load changes greatly, it can show a strong buffer capacity, and the reactor has a relatively strong load impact resistance.

(2) NH ₄ ⁺ -N concentration and its removal rate during startup

It can be seen from Figure 2 that in the initial stage of continuous water inflow, the removal rate of ammonia nitrogen increases rapidly with time. Within two days, the removal rate of ammonia nitrogen increases from 73.7% to 85.96%. When changing within the L range, the removal rate of ammonia nitrogen remains above 60%, and the highest can reach 86.5%.

Like the removal of organic matter, there are also obvious fluctuations. Overall, the biological aerated filter has a good removal effect on ammonia nitrogen. It can also be seen that when the concentration of ammonia nitrogen in the influent is maintained at 50±3mg/L, the ammonia nitrogen in the effluent is all around 10mg/L. From the 20th day to the 26th day, the concentration of ammonia nitrogen in the influent changed greatly, but the removal rate of ammonia nitrogen was relatively stable, ranging from 74.4% to 79.7%, which indicated that after a period of domestication and cultivation, the biofilm had formed and gradually matured. There is a certain ability to resist shock loads.

2. Microscopic inspection results of biological aerated filter start-up

At the initial stage of start-up, the reactor was unstable and the quality of the effluent was poor. Microorganisms such as paramecium, rotifers, and branch worms could be observed in the effluent under the microscope. Paramecium indicated that the system load was low and the dissolved oxygen was low; During the operation of the device, it can be observed that there are a large number of bell worms in the effluent. The front edge of the worm body has a ciliated band (composed of two circles of cilia that can be moved), and the worm body is a typical bell shape, so it is called bell worms. , belonging to protozoa. Whether it is a single or a group of species, it grows very rich in the aeration tank and filter tank of the wastewater biological treatment plant, which can promote the flocculation of activated sludge, and can prey on a large number of free bacteria to clarify the effluent. The large number of clock worms is a manifestation of the mature growth of activated sludge, indicating that the treatment effect is good.

3. Optimization of operating parameters of biological aerated filter

(1) hydraulic load

Under the operating conditions of pH 7.5-8.5, influent COD concentration of 300mg/L, and NH4 ⁺ -N concentration of 30mg/L. Effect of hydraulic load on COD and NH4 ⁺ -N removal rate when changing from 0.03m ³ /(m ² ·h) to 0.06m ³ /(m ² ·h). The effect of hydraulic loading is shown in Fig. 3.

It can be seen from Figure 3 that the removal rate of COD and ammonia nitrogen both increased first and then decreased with the increase of hydraulic load. When the hydraulic load increases from 0.03m ³ /(m ² ·h) to 0.04m ³ /(m ² ·h), the average removal rate of COD increases from 56.20% to 83.16%, when the hydraulic load continues to increase to 0.06m ³ / (m ² ·h), the average COD removal rate decreased again to 74%, so when the water conservancy load was 0.04m ³ /(m ² ·h)), the COD removal rate was the highest. Similarly, the removal rate of NH ₄ ⁺ -N is also maximum when the hydraulic load is 0.04m ³ /(m ^{2 ·} h). At this time, the removal rate of ammonia nitrogen is 81.26 ^% . h) or increased to 0.06m ³ /(m ² ·h) ammonia nitrogen removal rates were reduced to 72.50% and 75.01%.

^The results show that: under the condition of ensuring sufficient hydraulic retention time, the biological aerated filter has a certain ability to resist the impact ^of hydraulic load. The filter reactor can guarantee a high removal rate of organic matter and ammonia nitrogen.

When the hydraulic load is less than or greater than 0.03～0.06m ³ /(m ² ·h)), the COD removal rate and ammonia nitrogen removal rate both decrease. Because maintaining a certain gas-water ratio, the hydraulic load is too high, the contact reaction time between microorganisms and the substrate is reduced, which is not conducive to the removal of pollutants; at the same time, the higher filtration rate also increases the flow rate and hydraulic shear between the filter layers. The force makes the biofilm easier to be eluted, which reduces the removal efficiency of pollutants. Moreover, increasing the hydraulic load also means reducing the hydraulic retention time (HRT), and the slower-growing nitrifying bacteria, nitrosifying bacteria, will be in a disadvantageous position in the competition with the carbonizing heterotrophic bacteria, and the overall activity will decrease, thereby reducing the overall reactor capacity. Nitrifying ability.

(2) Air-to-water ratio

Under the operating conditions of pH 7.5-8.5, hydraulic load 0.04m ³ /(m ² h), influent COD concentration 300mg/L, NH ₄ ⁺ -N concentration 30mg/L, the gas-water ratio is The effects of 3:1, 6:1, and 12:1 on COD, NH ₄ ⁺ -N removal rate, and the effect of different gas-water ratios are shown in Figure 4.

It can be seen from Figure 4 that with the gradual increase of the air-water ratio, the removal capacity of the biological aerated filter for COD and NH ₄ ⁺ -N also gradually increases. When the air-water ratio increases from 3:1 to 6:1, the removal rates of COD and NH ₄ ⁺ -N increase from 66.71%, 76.17% to 79.85%, 80.6%, respectively, and the increase is relatively obvious. When the air-water ratio increased from 6:1 to 12:1, the removal rate of COD and NH ₄ ⁺ -N increased but not obviously, and the increase of COD removal rate was less than 1%.

The results show that: biological aerated filter has high oxygen utilization and conversion capacity. When the air-water ratio is 6:1, a good oxygenation effect can be obtained, so that aerobic bacteria can grow well, and the reactor shows a stable treatment effect. With the increase of aeration rate, the degree of liquid turbulence caused by air bubbling increases, which is conducive to the transfer of oxygen in the gas phase to the water and the surface of the filler, and the concentration of oxygen in the reaction system increases, providing sufficient oxygen for aerobic microorganisms. , so the removal rate of pollutants increases with the increase of aeration rate. However, if the aeration rate is too large, the concentration of oxygen in the reaction system is limited by the equilibrium solubility, and the dissolved oxygen will not increase, but the excessive turbulence will cause the analysis of dissolved oxygen in the water and the shedding of the biofilm on the filler, reducing the concentration of immobilized microorganisms. The concentration is not conducive to the removal of pollutants. And too much aeration will increase power consumption.

Example 2

Mix walnut shells and zeolite in a volume ratio of 2:1 as the filler of the biological aerated filter, and start operation in the same manner as in Example 1. The monitoring results show that it takes 23 days for the biological aerated filter to successfully form a membrane at this time, and the COD and NH ₄ ⁺ -N removal rates were 73.3% to 87.5% and 63.2% to 77.4%.

Example 3

Walnut shells and zeolite are mixed evenly as the biological aerated filter filler in a volume ratio of 4:1, and start operation in the same manner as in Example 1. The monitoring results show that it takes 27 days for the biological aerated filter to successfully form a film at this time. The removal rates of COD and NH ₄ ⁺ -N can reach 71.8%-89.6% and 65.1%-80.6%, respectively.

Compared with other fillers, the combined filler of the biological aerated filter of the present invention has a faster film-forming speed under the same conditions, and it only takes about 20 days for the successful film-forming; it has a good removal effect on pollutants (COD, NH ₄ ⁺ -N) ,

In addition, the filler is common agricultural waste with wide sources and low price, and is suitable for mass use.

Claims (5)

1. a BAF combined stuffing, is characterized in that, is made up of nut-shell and zeolite, and wherein the volume ratio of nut-shell and zeolite is 2 ~ 4:1.

2. BAF combined stuffing according to claim 1, is characterized in that, the median size of nut-shell and zeolite is 4 ~ 6mm.

3. the application of combined stuffing in BAF, is characterized in that, specifically implements according to following steps:

Step 1, the static biofilm stage

Be nut-shell and the zeolite of 4 ~ 6mm by median size be that 2 ~ 4:1 mixes rear loading BAF by volume, and active sludge is injected in filter tank and carry out stewing exposing to the sun, make mud activity recovery, mud dosage is as the criterion to fill filter tank, intakes after seed sludge with the little water yield, and passes into air and carry out aeration agitation, every 24 hours by filter tank 1/3 upper solution take out, and supplement simulated wastewater, every day, periodic monitor reactor effluent quality, namely monitored pH, DO, COD and NH ₄ ⁺-N, and examine under a microscope microbial growth situation on filler, enter into the cultured continuously stage after 7 days;

Step 2, the cultured continuously stage

Discharge and fail the suspension microorganism of effective biofilm, pass into air with simulated wastewater continuum micromeehanics, the hydraulic detention time keeping biological filter is 12h, keep dissolved oxygen concentration at 4mg/L during biofilm, under the prerequisite that dissolved oxygen concentration meets the demands, reduce aeration rate, timing every day detection reaction device effluent quality, namely monitors pH, DO, COD and NH as far as possible ₄ ⁺-N, and observe microbial growth situation on filler; If effluent quality fluctuation is less, COD and NH ₄ ⁺-N clearance tends towards stability, and to can be observed in water outlet containing more campanularian under the microscope, illustrates to cultivate through domestication after a while, and microbial film has been formed and growth and maturity just gradually, has stronger anti-load impact ability, determines biofilm success;

Step 3, the BAF operation phase

After biofilm success, pH value 7.5 ~ 8.5, inlet COD concentration are 300mg/L, NH ₄ ⁺-N concentration is run under 30mg/L condition, and every day, periodic monitor reactor effluent quality, namely monitored pH, dissolved oxygen, COD, NH ₄ ⁺-N, NO ₂ ^--N and NO ₃ ^--N water-quality guideline.

4. the application of combined stuffing according to claim 3 in BAF, is characterized in that, in step 1, aeration rate is 9L/h, adopts intermittent aeration, leaves standstill 1h with culturing micro-organisms after aeration 3h.

5. the application of combined stuffing according to claim 3 in BAF, is characterized in that, in step 3, aeration rate is 9 ~ 12L/h, hydraulic load 0.03 ~ 0.06m ³/ (m ²h), gas-water ratio is 3 ~ 12:1.