WO2002081387A1

WO2002081387A1 - Apparatus for treatment of wastewater, including a biofilter and a post-filter

Info

Publication number: WO2002081387A1
Application number: PCT/FI2002/000260
Authority: WO
Inventors: Juha Huhta
Original assignee: Green Rock Oy
Priority date: 2001-03-27
Filing date: 2002-03-27
Publication date: 2002-10-17
Also published as: FIU20010133U0; FI5036U1

Abstract

A wastewater treatment apparatus according to the present invention includes a biofilter with a known structure and operating principle, in which organic impurities in the wastewater are removed by means of decomposing microbes. The biofilter has a tank (4) containing fill material (8) which functions as a substrate for microbe growth. Water undergoing treatment is fed into the tank, and after passing through the fill material said water exits to post-treatment. For post-treatment of the waste-water, the apparatus has its own post-treatment unit, or post-filter. The post-filter contains a filter layer (24) with which particles and sludge slicks formed as a result of microbe activity are removed from the water. The material of the filter layer is advantageously mineral wool. The post-filter can be located inside the tank of the biofilter, whereupon the apparatus can be assembled inside one shell structure as an installation-ready package.

Description

Apparatus for treatment of wastewater, including a biofilter and a post-filter.

The present invention concerns a wastewater treatment apparatus, which includes a biofilter having a tank which holds wastewater undergoing treatment and inside said tank, fill material which functions as a substrate for microbe growth.

Biofilters are commonly used in wastewater purification. A biofilter includes a basin or tank containing fill material which functions as a growth substrate for microorganisms. Various materials, such as crushed aggregate, plastic cells or mineral wool, may be used as a fill material. Wastewater undergoing purification is fed through the fill material from the top down while air is simultaneously fed into the fill material. This creates favorable conditions for microbe activity inside the filter. Micro-organisms living on the surface of the fill material consume organic material in the wastewater as nutrition, whereupon the wastewater is purified. Said filter also usually includes a pump which circulates the wastewater through the fill material several times. Biofilters may be manufactured in different sizes, depending on the purifying capacity required. Filters may be large parts of municipal wastewater purification plants or small apparatuses of individual buildings, but their operating principle is nevertheless the same.

When microbe growth on the surface of the fill material reaches a specific thickness, it begins to flow downward along with the water. For this reason, water purified by means of a biofilter needs to be post-treated to remove microbe growth suspended in the water. For post-treatment, a settling basin, into which treated water from the filter is fed, needs to be constructed in conjunction with the biofilter. In the settling basin, growth which is heavier than water settles to the bottom of the basin, after which the purified water is fed out of the purification apparatus.

A wastewater purification apparatus according to the prior art contains several disadvantages. Treatment of large quantities of wastewater requires large post-settling basins, which are expensive to construct. Construction of said basins also requires a large land area, for which reason they cannot be located in confined areas. Due to a lack of space, it is practically impossible to expand many existing municipal purification plants. Furthermore, because the wastewater remains in the settling basins for a relatively long time, the wastewater purification process is slow. Neither is it possible to remove the finest particles in the wastewater by means of settling basins, whereupon the purification capacity of the apparatus is inadequate. The purpose of the present invention is to present an improved wastewater treatment apparatus which diminishes said disadvantages and flaws associated with apparatuses according to the prior art. A wastewater treatment apparatus according to the present invention is characterized by what is presented in the inventive claims. Certain advantageous embodiments of the present invention are presented in the dependent claims.

A wastewater treatment apparatus according to the present invention includes a biofilter with a known structure and operating principle, in which organic impurities in the wastewater are removed by means of decomposing microbes. The biofilter has a tank containing fill material which functions as a substrate for microbe growth. Water undergoing treatment is fed into the tank, and after passing through the fill material said water exits to post-treatment. The basic idea of the present invention is that for post-treatment of the wastewater, the apparatus includes a post- filter used to remove from the water the particles and sludge slicks formed as a result of microbe activity. Thus, the present invention differs decisively from biofilters according to the prior art, in which post-treatment of wastewater takes place in settling basins.

In one advantageous embodiment of the present invention the post-filter is located inside the tank of the biofilter. This type of apparatus is an installation-ready package assembled inside one shell structure.

One advantage of the present invention is that is improves the quality of wastewater treatment, because it also removes fine particles from the wastewater which cannot be removed from the water by means of settling.

Another advantage of the present invention is that it requires little space, because the apparatus does not need a large settling basin.

Yet another advantage of the present invention is that is speeds up the wastewater purification process, because the slow settling phase is eliminated completely.

Yet another advantage of the present invention is that its structure is simple and well suited to industrial manufacture.

The present invention is described in detail below, with reference to the enclosed drawings. Figure 1 presents an exemplary cross section of a wastewater treatment apparatus according to the present invention,

Figure 2 presents an exemplary cross section of an advantageous embodiment of a wastewater treatment apparatus according to the present invention, and

Figure 3 presents an exemplary top view of the apparatus presented in figure 2.

Figure 1 presents a cross section of a wastewater treatment apparatus according to the present invention. Said treatment apparatus includes a biofilter 1 and a post- filter 2 arranged in the same conjunction. The body of the biofilter is formed by a cylindrical tank 4 open at the top and divided in the vertical direction into two parts by means of an intermediate floor 6. The space above the intermediate floor contains fill material 8, which may be any suitable material, such as crushed aggregate or plastic cells, and which functions as a growth substrate for micro-organisms. Advantageously, the fill material is sheet-like or trough-like mineral wool. The intermediate floor is a plate-like part containing holes or cracks through which water is able to flow.

Below the intermediate floor is a drip space 10 bordered by the floor of the tank, the intermediate floor and the vertical wall of the tank. The wall of the tank contains openings 12 through which air may flow into the drip space. Near the floor of the drip space is a drain pipe 14 through which wastewater treated in the biofilter may flow from the drip space to the post-filter 2. The biofilter also includes a feed pipe 16 through which wastewater undergoing treatment is fed into the biofilter. The feed pipe enters the tank through the lower part of the tank, from where the feed pipe passes through the intermediate floor 6 into the upper part of the tank, above the layer of fill material. The top end of the feed pipe branches into several branches containing holes or nozzles facing downward.

Said biofilter functions as follows. Wastewater undergoing treatment flows through the feed pipe to the top end of the feed pipe, from where the wastewater is directed through the holes onto the layer of fill material. The wastewater is lifted onto the layer of fill material by means of a pump 18 connected to the feed pipe. The waste- water gradually flows through the layer of fill material by force of gravity, whereupon microbes living in the fill material consume the organic material in the waste- water as nutrition, thereby purifying the water. When the water has flowed to the bottom part of the layer of fill material, the water flows through the intermediate floor into the drip space 10, from where the water exits via a drain pipe 14 to a post- filter. The biofilter may also include a return pipe 20 from the drip space to the pump 18, through which part of the water in the drip space may be fed back into the feed pipe 16. Part of the wastewater may be recirculated several times through the fill material by means of the return pipe, which naturally improves the purification capacity of the filter.

Water purified by means of the microbes is conducted from the drip space 10 of the biofilter through a drain pipe 14 to the post-filter 2, where suspended particles and sludge slicks formed as a result of microbe activity are removed from the wastewater. The post-filter consists of a basin body 22 containing a filter layer 24 inside. The size and shape of the filter layer is such that it fits snugly against the wall of the basin body on all sides. The material of the filter layer may be any material suitable for a filter. Advantageously the filter layer is sheet-like mineral wool. The filter layer is supported by a supporting net 26 inside the basin body in such a way that there is space above and below the filter layer for water undergoing treatment. The filter layer resting on the supporting net can easily and quickly be replaced when it becomes clogged. The drain pipe 14 from the drip space of the biofilter to the basin body leads to the space above the filter layer 24, and a drain pipe 28 exits from the basin body from the space below the filter layer. If necessary, the open top surface of the basin body can be covered by means of a removable cover. The post-filter may be a separate device installed in conjunction with the biofilter or it may be a fixed part of the structure of the biofilter. The wastewater undergoing treatment flows through the drain pipe to the top of the filter layer 24 and slowly flows through the layer, whereupon the solid particles in the wastewater become attached to the filter layer. Upon flowing through the filter layer the purified water flows through the drain pipe 28 out of the basin body. The purified water that has flowed through the post-filter can be conducted into a waterway or absorbed into the ground.

Figure 2 presents an exemplary vertical cross section and figure 3 presents an exemplary top view (without a cover) of an advantageous embodiment of a wastewater treatment apparatus according to the present invention. In said advantageous embodiment of the present invention a post-filter 2 is located inside a cylindrical tank 4, above fill material 8. The basin body 22 of the post-filter is ring-shaped, and it shares the same exterior wall with the tank 4. The basin body contains a filter layer 24, which is supported by an essentially horizontal supporting net 26 located near the bottom edge of the basin. The bottom 42 of the basin body is inclined, thereby forming a ring-like drain basin between the supporting net and the bottom, into which water that passes through the filter layer flows. A drain pipe 28 leading from the drain basin through the wall of the tank conducts purified water out of the purification apparatus. The treatment apparatus also includes a removable cover 48, which is installed over the open top of the tank 4. The purpose of the cover is to protect the interior parts of the tank against weather and other stress and give the apparatus a finished appearance.

The center of the tank contains a pump well 30, which contains two water pumps, a first water pump 32 and a second water pump 34. Said water pumps are submersible electric pumps which switch on automatically when water flows into the pumps through an opening near the bottom edge of the pumps. The pumps are connected to the electric power line by means of cords not shown in the figure. A lower lifting pipe 38 leads upward from the first water pump inside the pump well and branches into several branches above the layer of fill material. The branches of the lower lifting pipe contain holes or nozzles pointed in the direction of the fill material, which direct the water rising in the lower lifting pipe onto the layer of fill material. A higher lifting pipe 40 leads upward from the second water pipe inside the pump well and also branches at its top end into several branches above the post-filter 2. When the water level in the pump well has risen sufficiently high, the second water pump pumps water undergoing treatment through the higher lifting pipe onto the filter layer 24 of the post-filter. The branches of the higher lifting pipe also contain holes and nozzles which direct the water toward the filter layer.

The bottom end of the pump well contains holes 36 leading to the drip space 10, allowing the water in the pump well to rise to the same level as it is elsewhere in the tank 4. The first water pump 32 is located at the bottom of the pump well, on the bottom of the tank 4. The second water pump is installed at a slightly higher level in the pump well, whereupon it switches on only when the water level inside the pump well has risen sufficiently high.

The advantageous embodiment of a wastewater treatment apparatus according to the present invention presented in figures 2 and 3 functions as follows. Wastewater undergoing treatment flows through the feed pipe 16 into the drip space 10 and through holes 36 into the pump well 30. When the water level in the pump well rises to the switch-on level of the first water pump 32, said pump begins pumping water through the lower lifting pipe onto the layer of fill material. The pumped water flows through the layer of fill material and is purified biologically by means of microbe activity. Water that has flowed through the layer of fill material flows through the intermediate floor into the drip space, from which the first pump again pumps it onto the layer of fill material. The water can be continuously recirculated through the fill material by means of the pump, which improves the purification process. A timer or clock switch (not shown in the figure) may be connected to the first pump, whereupon the pump runs continuously for a preset period of time. Oxygen required by the microbe activity is mixed into the wastewater undergoing treatment when the water is sprayed from the lower lifting pipe onto the layer of fill material, so the apparatus does not necessarily need any other aeration. If necessary, however, aeration can be made more effective by means of an aeration pipe 46 leading into the drip space, which allows air to also flow through the intermediate floor directly into the space below the layer of fill material.

When the water level in the tank 4 and the pump well 30 rise to the switch-on level of the second water pump 34, the second water pump 34 begins to pump water through the higher lifting pipe 40 to the post-filter 2. The water is directed through holes in the branches of the higher lifting pipe onto the filter layer 24, through which the water flows into the drain basin 44 and from the drain basin through the drain pipe 28 out of the purifier. When the water level in the tank and the pump well goes down enough as the result of pumping, the second water pump automatically switches off. Fine particle-like impurities in the water become attached to the filter layer, whereupon the water flowing through the filter is purified. The material of the filter layer is advantageously sheet-like mineral wool, which has a very good filtration capacity. When the filter layer becomes clogged with the attached particles, the filter layer is simply replaced with a new one, whereupon the apparatus is again functional. The used, clogged filter layers can be advantageously disposed of by composting them.

The wastewater treatment apparatus presented in figures 2 and 3 can be constructed into a compact device, for example, approximately 1.5 - 2 meters high and approximately two meters in diameter. The tank 4, intermediate floor 6 and pump well of the apparatus are advantageously made of plastic and the fill material and filter layer are made of mineral wool. Said purification apparatus is compact and lightweight, making it easy to transport in a passenger car trailer, and installation by hand is possible without heavy lifting equipment. The apparatus can be installed above ground or advantageously it can be placed in a pit dug into the ground in such a way that the top surface of the tank is slightly above ground level. Said apparatus is also especially suitable as a building-specific wastewater treatment apparatus in vacation centers, row houses and small groups of houses. A wastewater treatment apparatus according to the present invention can be used alone or it can be con- nected to other wastewater treatment units, such as chemical wastewater treatment apparatuses.

Certain advantageous embodiments of a wastewater treatment apparatus according to the present invention are described above. The present invention is not limited to the embodiments described above, but rather the inventive idea can be applied in numerous ways to the extent allowed by the enclosed claims.

Claims

1. A wastewater treatment apparatus, which includes a biofilter (1) having a tank (4) which holds water undergoing treatment and inside said tank, fill material (8) which functions as a substrate for microbe growth, characterized in that said apparatus also includes a post-filter (2) for post-treatment of biologically purified waste- water.

2. The wastewater treatment apparatus according to claim 1, characterized in that the post-filter (2) is permanently affixed to the tank (4).

3. The wastewater treatment apparatus according to claim 1 or 2, characterized in that the post-filter is located inside the tank (4).

4. The wastewater treatment apparatus according to one of the claims 1 - 3, characterized in that the post-filter (2) includes a basin body (22), inside which is a filter layer (24) for removing solid particles from the water undergoing treatment.

5. The wastewater treatment apparatus according to claim 4, characterized in that the material of the filter layer (24) is mineral wool.

6. The wastewater treatment apparatus according to one of the claims 1 - 5, characterized in that the apparatus includes a first water pump (32) and a lower lifting pipe (38) for transporting water onto the fill material (8).

7. The wastewater treatment apparatus according to one of the claims 1 - 6, characterized in that the apparatus includes a second water pump (34) and a higher lifting pipe (40) for transporting water into the post-filter (2).

8. The wastewater treatment apparatus according to one of the claims 1 - 7, characterized in that the tank (4) contains a pump well (30) and that the first and second water pumps (32, 34) are located in said pump well.