KR910003087B1 - Treatment of water - Google Patents

Abstract

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Description

Water treatment method and device

1 is a schematic top view of a wastewater lagoon for carrying out the invention.

2 is a schematic top view of another wastewater lagoon for carrying out the invention.

3 is a cross-sectional view taken along line III-III of FIG.

4 is a sectional view taken along the line IV-IV of FIG.

* Explanation of symbols for main parts of the drawings

102 tank 112 intermediate wall

114, 116 treatment area 118 inflow area

120: inlet pipe 124, 126: beam

128, 130: channel 132, 134: outflow pipe

140: pump 148: spraying pipe

152: surface ventilator 154: water tank

164 pump 166 recovery pipe

202 tank 214, 216 treatment area

218: intermediate region 220: inflow pipe

224, 226: Bo 228, 230: Channel

240: pump 248: spraying pipe

254: tank 266: recovery pipe

278: Surface ventilator

The present invention relates to a method and apparatus for treating water having a biochemical oxygen demand (BOD). The term "water with biochemical oxygen demand" as used throughout the text refers to water with biochemical oxygen demand or other naturally obtainable water sources, or wastewater or other effluents with biochemical oxygen demand. Water).

It is conventionally known to treat water having a biochemical oxygen demand in a so-called "lagoon" or oxidation promoter. However, the rate at which water can be treated in such a lagune or oxidation promoting agent is relatively limited, and the conventional treatment method applied at the time of laungoon and oxidation promotion needs to be improved. It is also necessary to treat water with biochemical oxygen demand in containers such as rainfall tanks that are commonly used to hold water well until it is passed into the treatment vessel or apparatus. Lagune, oxidation promoters and surplus tanks are all characterized by relatively shallow. Such a container will be referred to herein as a "shallow tank."

Typically, treatment of wastewater to reduce its biochemical oxygen demand can be carried out by a group of bacteria known as activated sludge effective to destroy contaminants or other harmful substances in water. Thus, such treatment typically requires a means for keeping the bacterial populations afloat in water and a means for aeration or oxygenation of water to maintain the essential oxygen conditions that bacteria require for breathing purposes. . Moreover, to purify the water to be recovered from the treatment vessel, a means for segregating the bacterial group and separating the water from the bacterial group is required. Typically this precipitation is carried out in a vessel separate from the treatment vessel. However, it is advantageous to simultaneously carry out treatment and precipitation of water in the same tank by the method described in the applicant's British Patent No. 1,596,311 or British Patent Application No. 2,118,449 (these patent documents are not necessary for the understanding of the present invention). Do.

In particular, where there is a need to increase the "biochemical load" of ragoons or oxidation promoters, the installation of a separate sedimentation tank is costly and easily invested in capital. Moreover, when the method described in the above-mentioned British Patent No. 1,596,311 is carried out in a shallow tank, the purification is difficult or impossible. Thus, as mentioned above, the known treatment of water with a biochemical oxygen demand is not suitable for carrying out such treatment in shallow tanks.

It is an object of the present invention to provide a method and apparatus for treating water having a suitable biochemical oxygen demand when it is required to be treated in a shallow tank.

In the water treatment method having the biochemical oxygen demand of the present invention, the step of (a) mixing the water with oxygen in the presence of suspended oxygen bacteria effective for reducing the biochemical oxygen demand of the water and the upper layer of the treated water are relatively aseptic. (B) precipitating the bacterial population, wherein water is treated simultaneously in at least two zones, and in the other zone step (a) while steps (a) and (b) are carried out in one zone. And step (b) are carried out in an abnormal state.

Both regions are formed in the same vessel so that the method of the present invention can be carried out in water contained in a shallow tank. Typically, but not necessarily, the two zones have a common inlet port. Therefore, the treated water in the area where the bacterial group is precipitated is discharged when it is introduced for the treatment of water having a biochemical oxygen demand. It is therefore possible for a continuous process to be carried out by the method according to the invention.

In general, it is important to allow water for treatment to flow into the remote part of the tank drain. It will be appreciated that the water coming in from a single vessel tends to migrate towards the area during precipitation. In addition, steps (a) and (b) are adjusted to have the same time and less than the average residence time of water in the tank. Typically each step (a) or step (b) of the method according to the invention is carried out for a short time (for example about half an hour) before the other steps are carried out continuously in the same zone and the residence time of the water in the tank. Reaches hours. The time of each step (a) and (b) depends on the biochemical oxygen demand of the water and the ambient temperature. If the water has a relatively high biochemical oxygen demand, the time is required to be relatively short for 50 minutes in a high temperature climate in order to settle the bacterial group in good condition, whereas in the temperate climate or when the biochemical oxygen demand is low, each step ( The time in a) and step (b) requires almost an hour. Typically relatively purified water flows out of the shallow tank beyond the beam remote from the inlet. An outflow channel or conduit is to be provided downstream of the beam.

At least one partition wall or baffle or other means is arranged in such a way that the water does not move from one area to the other in order to partition the two areas mentioned above in a single tank. In particular two different configurations are conceivable. In one configuration, two longitudinally extending areas communicate with the outlet beam (or similar means) near one end of the tank and with the common inlet area near the other end. In another configuration, the two zones are separated from each other by an intermediate region of longitudinal extension into which water for treatment is introduced.

The present invention also provides an apparatus for treating water having a biochemical oxygen demand, comprising: a shallow tank having at least two treatment zones, means for effluent water from the treatment zone, and means for effluent water. At least one remote water inlet, means for stirring water in the treatment zone, and means for oxygenating the treatment zone, the apparatus being adapted to carry out the above-mentioned method.

Typically the oxygenation and agitation means operate intermittently so that coralization and agitation occur in one treatment zone at one time (ie only two treatment zones). Therefore, the water in the other side will be relatively stable, and the sedimentation will move over the outflow beam so that purified water is discharged from the thin tank. During the agitation of the water containing the flocks, some water (containing the bacillus) will collect in the outflow channel associated with the beam beyond the outflow beam associated with the adjacent area (or through another outflow device). Typically, these channels are equipped with valves, which open only while the purified water is discharged into the channel beyond the associated beam. The water in the region associated with the beam and the outflow channel is coralized and with agitation of this region, some water (containing floating bacterial populations) moves beyond the beam into the channel and stagnates there. It is desirable to recover such water containing bacterial groups from the channels and back into the shallow tanks. This is done immediately after step (a) to prevent contamination of the purified water from the area during step (b). To this end, a single tank is associated with each channel and is sent to the tank under the action of gravity or a pump that contains suspended bacterial populations, and then to a shallow tank as needed.

Although a means for oxygenating and stirring water is provided separately, the methods described in the Applicant's British Patent No. 1,455,567 can be used to perform these two functions. In this method, water is withdrawn from one region, oxygen is injected under bridge conditions to allow the water to be compressed and to disperse bubbles that do not dissolve in water (also oxygen will be dissolved), and these bubbles can be treated. Oxygen bubbles that are not dissolved by being recovered into the water region and injected into this area will be divided into fine bubbles and easily dissolved. By injecting this water in the form of jets of oxygen bubbles at several different points or locations, the required degree of disturbance in the area of the water to be treated can be achieved. The pressure exerted on the withdrawn water can be selected to provide energy for stirring the water in the oxygenated region.

If necessary, the water can be vented with coral. Such aeration can be carried out equally in the region to be oxygenated or in a separate region. This has the advantage of helping to counteract the carbon dioxide produced by bacteria which create acidic conditions that are unfavorable to the water to be treated. This is because it helps to replace carbon dioxide from the solution.

The advantages of the method and apparatus according to the invention can be readily converted so that the present lagoon or large tanks for the treatment of waste water can be carried out without the need for a large capital, for example without the need for installing a sedimentation tank. have. Thus, it is possible to spend relatively little capital on converting a current treatment tank into a tank for the treatment of water having a biochemical oxygen demand, or to increase the "biochemical load" during current lagoons or oxidation promotions.

The method and apparatus according to the present invention will be described in more detail with reference to the accompanying drawings.

In Figures 1-3, a rectangular tank 102 is shown. The tank has side walls 104, 106 and end walls 108, 110. The tank is relatively large in size. However, the depth of the tank is shallow compared to the lengths of the walls 104, 106. Typically walls 104 and 106 are 50 meters long and walls 108 and 111 are one quarter or one fifth, or 10 meters, of this length. The tank 102 has an open top surface whose top surface corresponds to the height of the ground, and the base of the tank is located below the ground. It is not necessary to install the tank 102 specifically to carry out the method according to the invention. In practice it is preferred that the method according to the invention be carried out in an already installed tank.

In tank 102 an intermediate wall (or baffle) 112 is installed in the tank to carry out the invention. This wall 112 is located at the same distance between the walls 104, 106 and extends parallel to the walls 104, 106 from the wall 110 toward the wall 108. The length of the wall 112 is about 80-90% of the length of the walls 104, 106. The wall 112 has two ends that are remote from the wall 110 and communicate with the inlet zone 118 where the inlet pipe 120 used to supply the biochemical oxygen demand into the tank 102 ends. The tank 102 is divided into treatment areas 114 and 116. Inlet pipe 12 is provided with a valve 122 that can cut off the supply if necessary. Typically the outlet end of the feed or inlet pipe 120 is disposed in the tank at a point on the same line as the longitudinal axis of the wall 112. The height of the wall 112 is chosen so that water does not flow directly over the wall while the present invention is performed. The structure also does not have a lower passageway for water to flow from one side 114 to the other 116 or vice versa. However, the wall does not need to be impermeable to prevent water from passing through the wall since there is no different head between the regions 114 and 116. In practice, the wall 112 is of a simple and lightweight structure, and may be suitably composed of, for example, a mounted taapoline or plastic sheet, or a coal brick. This wall may allow the oxygenation process to be performed in the other region while performing the supernatant function of the purified water in one of the regions 114, 116. Treatment zones 114 and 116 are provided with beams 124 and 126 through which the water treated in the process according to the invention can pass from the tank to the respective channels 128 and 130. The beams 124, 126 and their respective channels 128, 130 are provided around two corners at each end of the tank 102 remote from the inlet area.

In the tank shown in FIG. 1, the beams 124, 126 can be constructed by appropriately adjusting the height of the wall 110 of the tank 102 (or a suitable beam can be installed in the tank 102, at which time The walls 104, 106, 110 need not be modified to some of them to act as beams). Channels 128 and 130 are not in communication with each other. However, channel 128 is in communication with outlet pipe 132 with valve 136. In a similar manner, channel 130 is in communication with outlet pipe 134 having valve 138. If necessary, the channels 128 and 130 may be integrally formed with the pipes 132 and 134. Regions 114 and 116 are provided with oxygenation means.

Each region 114, 116 is associated with a pump 140. Each pump 140 is provided with supply conduits 142 derived from the respective treatment zones 114, 116. Each pump 140 has a recovery conduit 143 having a venturi 144 formed at a portion close to the pump 140. In the venturi 144, the oxygen pipe line 146 is guided to the narrow portion of the venturi 144 so that oxygen is sucked from the pipeline 146 to the recovery line 143 during the oxygenation process. Each oxygen pipe line 146 is in communication with a commercially available pure oxygen source (not shown). The return line 143 ends at the sparge pipe 148 extending below the water surface in the tank 102. The sparging pipe 148 has a plurality of pores 150 from which a relatively high rate of oxygen diffusion into the water is propelled into the respective regions 114 and 116 in the course of the process according to the invention. I'm going. The structure of this sidestream oxygenation system is described in more detail in Applicant's British Patent No. 1,455,567.

The jet of oxygenated water by sparging pipe 148 allows for effective agitation in each region 114, 116. Therefore, the bacterial group remains suspended in the area during the oxygenation process. As shown in FIG. 1, the areas 114 and 116 are provided with a surface ventilator 152 having a known structure. It is not necessary to install such vents, but it will be appreciated that if they are installed they will stir water and float the bacterial population. This vent 152 helps to replace the carbon dioxide generated by the bacteria and facilitates maintaining the pH of the water within the required range.

The agitation that occurs during the operation of the vent and oxygenator in zone 114 or zone 116 causes some of the water suspended in the bacterial population to cross over pedestrians 124 and 126 to each channel 128 and 130. Will flow. It will be appreciated that during the oxygenation process of each zone, the channel associated with that zone is closed (ie valves 136 and 138 are closed in this case). Therefore, after the oxygenation process, the floating bacterial group can be settled, and water containing the floating bacterial group is withdrawn from the channel and recovered to the tank to prevent loss of the bacterial group. To this end, the channels 128 and 130 are in communication with the water tank 154 through the inlet pipes 156 and 158 having the valves 160 and 162, respectively. The water tank 154 is provided with a pump 164 for recovering water from the channels 128 and 130 to the tank through the recovery pipe 166 having the valve 170. Typically recovery pipe 166 extends to inlet pipe 120.

The operation of the device shown in FIGS. 1 and 3 is as follows.

The tank 102 is supplied with wastewater for treatment. Two stages of processing are performed in each of regions 114 and 116. Each two-step treatment consists of oxygenating the water in the presence of a flocculation group that effectively reduces the biochemical oxygen demand of the water and precipitating the bacterial population so that the relatively purified water can flow out of the tank. The processing step in one region is different from the processing step in the other region. In other words, while the precipitation step is performed in one region, the oxygenation step of water is performed in the other region or vice versa.

When oxygenation occurs in zone 114 while precipitation occurs in zone 116, valve 122 of inlet pipe 120 opens and valve 138 of channel 130 also opens while the other valve 136. , 160 and 162 are in a closed state. In addition, pump 140 and vent 152 in region 114 are actuated while pump 140 and vent 152 in region 116 are inoperative. Similarly, the pump 164 coupled to the bath 154 does not work.

Pump 140 associated with zone 114 draws water from the zone and increases its pressure to around 2-4 bar. Pressurized water is oxygenated to form oxygen-containing dispersed water containing bubbles of relatively small oxygen. Typically only 40-60% of the oxygen injected into the pressurized water is dissolved and the remainder remains dispersed.

This dispersion water is sparged into the water in the area 114 and when the jet of the dispersion water enters the water in the area 114, the pressure drops and the bubbles of oxygen are divided into finer bubbles. This facilitates the dissolution of oxygen bubbles. Such oxygenation techniques are described in detail in British Patent No. 1,455,567. The jet of dispersed water disturbs the water in the region 114 to keep the bacterial group naturally floating in the water (or the so-called activated sludge supplied to the water) in the suspension. Bacteria assimilate oxygen to destroy contaminants in wastewater, thus reducing the biochemical oxygen demand of the water. The bacterial group tends to multiply in oxygenated water by respiration of oxygen and in addition carbon dioxide is produced by the bacteria. This carbon dioxide is dissolved in water but at least a portion thereof is replaced by the action of the surface ventilator 152 operated during oxygenation of the water in the region 114.

Water will flow continuously through the beam 126 as it flows into the tank 102 to be treated through the inlet pipe 120. Thus, the drifting of water from the inlet pipe 120 toward the beam 126 will be made. Therefore, the settling time of the zone 116 and the rate of flow of water into the tank 102 are adjusted such that the amount of water entering the tank 102 during any one settling time in the zone 116 is less than the amount of water in the zone. do. Only a small amount of incoming water can be processed and left untreated. Typically the water in zone 114 is oxygenated for a time ranging from half to one hour, while zone 116 enters the precipitation process. At the end of this time the inlet valve 112 and outlet valve 138 are closed and the pump 140 and vent 152 associated with the region 114 are deactivated. Immediately after this, pump 164 of bath 154 is actuated and valve 160 is opened to allow water in channel 128 to be withdrawn from the bath. Water may then be recovered to the tank via pipe 158 (valve 170 is open) in a later step (or immediately). Excess bacterial populations can also be released to the environment. When channel 128 is drained (typically taking 1 or 2 minutes or less), the area where oxygenation occurred immediately before draining of the channel is converted to an oxygenation (and aeration) process. Thus, the inlet valve 122 and the outlet valve 136 are opened, and the pump 140 and the vent 152 associated with the region 116 are operated. Thus, water with little bacterial population flows out of tank 102 beyond beam 124 while water in region 116 is oxygenated and synchronized. At the end of the selected time (which is the same as the time selected for oxygenation of the region 114 and settling of the bacterial colonization of the region 116), the valves 122, 136 are again closed and the pump associated with the region 116 140 and the ventilator 152 is operated. The pump 164 is then operated and the valve 162 is opened to allow the water containing the bacterial group to be discharged from the channel 130. In addition, the function performed in each of the regions 140 and 116 may be diseased again so that oxygen may be oxygenated and treated in the region 114, while bacteria may be precipitated in the region 116. In doing so, a continuous process for the treatment of water may be provided.

If necessary, the operation of valves, pumps and vents can be controlled automatically. The valves 122, 136, and 138 may be penstock type.

The tank 202 in FIG. 2 and FIG. 4 is actually identical to the tank 102 shown in FIG. The tank 202 has side walls 204 and 206 and end walls 208 and 210. However, instead of the wall 112 shown in FIG. 1, two walls 274 and 276 are provided. These walls 274, 276 are spaced apart from each other and extend parallel to the walls 204, 206. Wall 274 extends from wall 210 toward wall 208 and terminates in front of wall 208. Typically the length of the wall 274 is 80% of the length of the walls 204, 206.

Wall 276 is the same length as wall 274 but extends from wall 208 toward wall 210. Thus, three regions are formed in the tank 204. The wall 274 and the sidewall 204 of the tank 202 form a first treatment region 216. Accordingly, water for treatment is supplied to the intermediate region 218 through the inlet pipe 220 having the valve 222. The intermediate or inlet zone 218 is in communication with the zone 216 at an end adjacent to the wall 204 of the tank 202. Inlet pipe 220 extends to the center of region 218. Walls 274, 276 are configured to prevent water from passing upward or downward upon operation of tank 202.

In FIG. 1 the outflow beam is constructed around the edge at the same end of the tank while in the device shown in FIG. 2 the outflow beam is diagonally opposed along the two sidewalls 204, 206 of the tank 202. It is formed at the corner. Water flowing over the beam 224 formed along the sidewall 204 flows into the channel 228 and out through the outlet pipe 232 with the valve 236. Similarly, water flows into channel 230 and out through outlet pipe 234 with valve 238. Regions 214 and 216 are equipped with the same oxygenator as already mentioned in FIG. Therefore, the construction and operation of such oxygenation device will be briefly described. Each oxygenator consists of a pump having an inlet pipe line 242 and a recovery pipe line 243 in which the venturi 244 is disposed. Each recovery pipe line 243 is connected with a spray pipe 248 disposed below the water surface of each treatment area. Each spraying pipe 248 is provided with pores 250 at regular intervals.

Unlike the device shown in FIG. 1, there are no vents in areas 214 and 216. Instead, a plurality of surface ventilators 278 are provided in the intermediate region 218.

An apparatus for draining the water in the channels 228 and 230 is provided. This device is similar to the device shown in FIG. The pump 264 is installed in the common water tank 254. The water tank 254 is in communication with the channel 228 through an inlet pipe 256 having a valve 260 and the channel 230 is in communication with the water tank 254 through a pipe 258 having a valve 262. have. A recovery pipe 266 having a valve 270 is provided. The recovery pipe 266 is connected to the inlet pipe 220 to return the bacterial group to the middle portion of the intermediate region 218.

The operation of the processing areas 214 and 216 is similar to the operation of the areas 114 and 116 mentioned in FIG. In other words, the device shown in FIG. 2 is similar except that there are no ventilation devices in the areas 214 and 216. However, the incoming water for treatment is fed to a relatively remote intermediate zone from zones 214 and 216 as compared to the position supplied to zone 118 in FIG. The oxygenation time and the rate of inflow of water into the tank 202 are selected so that bacterial populations settle out of the water in the zone 214 and the purified water flows out of this zone and no new water enters the zone 214 during this settling time. . When the bacterial group is precipitated in one side region of the tank 202 and the purified water flows out, it will be seen that water is introduced into the other side region. Typically the mean residence time of the wastewater in the intermediate zone 218 is equal to the oxygenation time.

The vent 278 is continuously operated in the intermediate region 218. In this respect the device shown in FIG. 2 is superior to the device shown in FIG. 1, and a commercially available vent can be operated continuously. Air dissolved in water helps to prevent acidification by the production of carbon dioxide by bacteria.

In other respects, the operation of the apparatus shown in FIG. 2 is the same as that of FIG. 1 and will not be described.

The flow of water from or into the device need not be stopped while water containing bacterial populations enters the water bath 254 from one of the channels 228, 230. Thus, valve 222 is left open during operation of the device. At the end of the oxygenation time in region 214, valve 238 is closed and valve 236 is open. At the same time valve 260 is opened. In such a case the bath 254 is not arranged as shown in FIG. Instead of the pump drawing water and bacteria from the channel 228 into the water tank 254, the suction force can sufficiently prevent the flow of water through the pipe 232. When the water drawn up by the pump is purged, the valve 260 closes, the pump stops operating and the purified water flows out through the pipe 232. The time taken for the operation of the pump can be determined empirically or according to its operation and the closing of the valves 260, 262 can be controlled automatically by a nephometer. Thus, the operation of all processes can be continued as a whole.

The method and apparatus according to the present invention provide many advantages. They can be used in existing oxidation-promoting tanks and can be used to convert basic sedimentation tanks into wastewater treatment tanks. Water purified by the present invention may be subjected to other treatments and may be discharged to rivers or other natural water sources.

Claims (5)

In the method of treating water having a biochemical oxygen demand, the method of oxygenation of water in the presence of suspended oxygen bacteria which reduces the biochemical oxygen demand of water (a) and the precipitation of bacteria so that the upper layer of the treated water becomes relatively sterile. And (b), wherein these two steps (a) and (b) are carried out alternately in water in two areas at the same time. The method of claim 1 wherein the two zones are formed in the same vessel and the solution is a shallow tank. The method according to claim 2, wherein, when the water having a biochemical oxygen demand flows in, the treated water flows out of the area where bacteria are precipitated, thereby performing a continuous treatment. The method as claimed in claim 2, wherein the two regions of water extend in the longitudinal direction and are in communication with an intermediate region in which water having a biochemical oxygen demand is supplied. The process of any of claims 2, 3 and 4, wherein step (a) withdraws a portion of the water from this region while step (a) is performed, pressurizing this portion of water, not dissolved in water. Injecting oxygen into a portion of the water under disturbing conditions to form a bubble dispersion, and returning the portion of the water to the region, and the oxygen bubble in which the returned water is injected into the region and does not dissolve is fine. The method of being divided into and easily dissolved.

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