JPH0487699A - Method for purifying polluted water region - Google Patents

Abstract

PURPOSE:To effectively purify a polluted water region by pumping up water in the water region, adding a flocculant to the water under aeration, forming sludge flocks, carrying out solid-liq. separation with an ultrafilter and returning the resulting filtered water to the water region. CONSTITUTION:Water in a pond L is pumped up and aerated in an aerating tank 2 by diffusing air from a compressor 3 or a blower through an air diffuser 4 set at the bottom of the tank 2. A flocculant in a flocculant tank 5 is added to the tank 2 by an injecting pump 6 and mixed with the water in the tank 2. This water is slowly stirred with a stirrer 9 in a subsequent mixing tank 7. The resulting clean water accompanied with sludge flocks formed in the tank 7 is drawn out of the middle part of the tank 7, pressurized by a pressurizing pump 12 and sent to an ultrafilter 13 with an incorporated ultrafilter membrane as a tube, hollow fiber or flat membrane type module. Clean filtered water 15 passed through the membrane is returned to other place of the pond L.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for effectively purifying polluted water bodies such as lakes, ponds, and moats.

[Conventional technology]

Conventionally, methods for directly purifying polluted water bodies include a method using an aerator called an intermittent air pump, a method of spraying lime or a flocculant, and the like.

[Problem to be solved by the invention]

However, although the former has the effect of preventing anaerobic decay by aerobizing the entire water body, it does not have the function of directly decomposing organic pollutants or removing them from the water body, so it is necessary to treat the pollutants. It has little effect. Furthermore, although the latter method temporarily shows remarkable effects such as improved visibility, it is not a permanent treatment for polluted water because sediment accumulates and anaerobic decomposition gradually progresses.

In order to effectively purify polluted water bodies, it is necessary to directly decompose soluble pollutants, or to adsorb or insolubilize them onto adsorbents, collect the adsorbents or sludge along with other solids, and discharge them out of the water area. There is. In particular, for phosphorus, which is a cause of eutrophication, the conventional method of purifying polluted water by coagulation and sedimentation is considered. Compared to water such as treated sewage water, the degree of phosphorus is low, so the flocs are weak and sedimentation is difficult. Further, even if sand filtration is provided at the latter stage, fine flocs reach the deep part of the filter tank, making backwashing difficult.

The present invention aims to effectively purify water bodies by adding a flocculant to water containing pollutants to form sludge flocs, performing solid-liquid separation, and returning clear water to the water bodies.

[Means to solve the problem]

The present invention was made to achieve the above object, and involves pumping water from a polluted water area, aerating it, adding a coagulant, etc., and separating the flocculated sludge into solid and liquid by ultrafiltration. The purpose is to purify water bodies by returning them to polluted waters.

[For production]

Water from polluted areas is pumped up, flocculants are added to produce sludge, solid-liquid separation is performed using an ultrafiltration device, the sludge is collected and transported out of the system, and the separated purified water is By returning the water to the water, the polluted water area can be effectively purified.

〔Example〕

The present invention will be explained below based on the illustrated embodiments.

In the figure, L indicates a small-scale pond as an example of a polluted water area, and a water pump 1 is provided at the end of the pond. The pumped pond water is aerated in the aeration tank 2 by dispersing air from a compressor 3 or a blower through an aeration device [4] at the bottom. Further, a flocculant is added from the flocculant tank 5 to the aeration tank 2 by an injection pump 6 and mixed with pond water. Furthermore, in the next mixing tank 7, the mixture is slowly stirred by a stirrer 9. A scraping device N8 for floating sludge is provided at the top of the mixing tank, and piping for drawing out the settled sludge is provided at the bottom, and the sludge is sent to the sludge coagulation tank by a sludge drawing pump 10.

The sludge flocs coagulated in the mixing tank 7 are pulled out from the middle stage of the mixing tank together with clear water, pressurized by a pressure pump 12, and sent to an ultrafiltration device 13. Ultrafiltration membrane N
13 is a module in which the ultrafiltration membrane has a tubular shape, a hollow fiber shape, a flat membrane shape, etc., and the clear filtered water 15 that has passed through the membrane is
It is sent back to another part of the pond. In order to prevent the filtered water 15 from being pumped due to a short circuit, it is more effective to provide a partition wall 16 in the pond and to return the filtered water to a position as far away from the water pump 1 as possible. Sludge flocs that do not pass through the ultrafiltration membrane are concentrated and returned to the mixing tank 7 via the return pipe 14.

Next, the operation of the present invention will be explained.

The aeration tank 2 has the function of increasing dissolved oxygen by supplying oxygen to the pond water and mixing it with the added flocculant etc. in a short time. However, the location where the flocculant and the like are added is not necessarily limited to the aeration tank 2, and it is also possible to add the flocculant etc. immediately before flowing into the mixing tank 7.

The chemicals to be added are selected depending on the target components, such as a flocculant that flocculates soluble phosphorus, and an adsorbent that removes other pollutant components. In the next mixing tank 7, slow stirring is performed to promote agglomeration of flocs. When the sludge flocs are sent to the ultrafiltration device 13 together with water, they are pressurized and mixed into the mixing tank 7.
When the water returns to normal pressure, some of the air dissolved in the water precipitates out as fine bubbles, adheres to the sludge flocs, and works to lift the sludge to the surface. It is collected by scraping device N8 and carried out of the tank. Therefore, performing aeration before the mixing tank 7 not only promotes flotation and separation, but also increases the dissolved oxygen concentration in the filtered water returned to the pond, which has the function of keeping the pond water in an aerobic state. ing. Furthermore, the sludge concentrated by the ultrafiltration membrane N13 is returned to the mixing tank 7, and by returning the sludge, the removal rate of phosphorus is increased and the solid-liquid separability of the sludge flocs is also improved.

On the other hand, among the sludge flocs in the mixing tank, those with large and heavy particles gradually settle. In order to enhance the precipitation effect, it is desirable to periodically stop stirring I19 and allow the mixture to stand still. The precipitated sludge is pulled out by a live extraction pump, concentrated to 1% or more at 4 degrees Celsius in a thickening tank 11, discharged outside the tank, and subjected to treatments such as dehydration and then disposed of. Further, the separated water overflowing from the concentration tank 11 is returned to the IIl gas tank 2 and treated again because dissolved oxygen has decreased.

〔Effect of the invention〕

According to the present invention, water in a polluted area is pumped up, a flocculant is added while aerating the water, the pollutants are coagulated to form sludge flocs, and the filtrate is separated into solid and liquid using an ultrafiltration device. In addition to returning the sludge to the polluted water area, the sludge is recovered and disposed of using a combination of flotation and sedimentation, which is more effective in removing pollutants than conventional technology, and by returning clear water with high dissolved oxygen, Polluted waters can be effectively purified.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an apparatus for carrying out the method for purifying polluted water areas of the present invention. 1 is a water pump, 2 is an aeration tank, 3 is a compressor, 4 is an aeration device, 5 is a flocculant tank, 6 is an injection pump, 7 is a mixing tank, 8 is a dirt & scraping device, 9 is an agitator, 10 is a sludge extraction pump, 11 is a sludge transfer tank, 12 is a pressurizing pump, 13
is an ultrafiltration device, ]4 is a return pipe, 15 is filtered water, 16
is a partition wall.

Claims (1)

[Claims] (1) Purify the water area by pumping water from the polluted water area, performing aeration, adding a flocculant, etc., separating the flocculated sludge from solid-liquid through ultrafiltration, and returning the filtered water to the polluted water area. A method for purifying polluted water bodies, characterized by: