WO2009082237A1

WO2009082237A1 - Apparatus and method for purification of waste water

Info

Publication number: WO2009082237A1
Application number: PCT/NO2008/000452
Authority: WO
Inventors: Rune Bakke
Original assignee: Waterment As
Priority date: 2007-12-21
Filing date: 2008-12-16
Publication date: 2009-07-02
Also published as: NO330212B1; NO20076606L

Abstract

Apparatus and method for treatment of wastewater and odorous fumes therefrom with low mechanical complexity. The apparatus consists of 3 chambers (I, II, III) to which one air pump (7a) provides aeration of activated sludge and biofilm processes. The same pump (7a) acts to obtain sludge return from sedimentation zone (6) to a mixed bioreactor zone (4), acts to pump liquid up through the sedimentation zone to obtain a suspended sludge bed, and provides pumping action to obtain mixing of the bioreactor zone (4), and flushing of odorous gasses from the first treatment stage (I) to the final treatment stage (III) where the odours are adsorbed and removed by biological reactions. The treatment capacity of the final stage, a trickle filter (9), is enhanced by integrating at least one equalisation tank (8) within the filter mass of the trickle filter.

Description

Apparatus and method for purification of waste water

Field of the invention

The present relates to the design of a process to remove dissolved and particulate pollutants from wastewater.

Background

Many houses, recreational homes, huts etc., not connected to public sewers, have separate toilet waste handling. The remaining wastewater from washing and kitchen activities, termed grey water, also needs treatment. Available solutions are quite expensive and/or complicated even though grey water is much less demanding to treat than normal domestic wastewater as it does not contain faeces, urine or toilet paper.

Existing solutions for grey water require bio filters almost as large as for normal wastewater to be able to handle the large load variations. Some use buffer tanks before the bio filter to equalise the flow, pumping the water from the tank to the bio filter to even out the large variations in wastewater flow. During periods when the filter is not in use, and there is no water to be treated, the filter can dry out, damaging the culture, causing a period of low treatment efficiency when the filter is again put in use. Other solutions use pumps to recycle the water from a tank after the bio filter back to the bio filter to increase the contact time between the water and the filter media. Existing solutions produce environmentally unfriendly gasses with unpleasant odours and are therefore equipped with ventilation above the building roof to disperse the odours and reduce nuisance.

Grey water treatment plants on the market consists of a filter unit or a septic tank as the first treatment step. The next and final step of these plants is a trickling filter which is quite large since this is the only biological treatment element in these plants. Trickle filters are the oldest technique for biological wastewater treatment, invented in Germany in the mid eighteen hundreds. It is not an efficient method and sensitive to load variations typical for small grey water treatment applications. The large size of these trickle filter chambers has two main disadvantages: Firstly they require large space (typically a large hole in the ground) and secondly they require a rather elaborate water distribution system on the top to make sure that the water is distributed over the whole filter medium. An alternative solution to the trickle filter sometimes used is a constructed wetland, but this also requires large space and considerable construction work. None of these solutions are equipped with air treatment and can therefore cause foul odours. Object

It is an objective of the present invention to provide a method to adequately treat wastewater, and the odours from this, in a process which can be conducted in portable tanks or containers and operated with low energy costs and other costs. It is a further object of the invention to provide an apparatus suited for conducting such a method, the mechanical complexity and construction costs of which are kept at a minimum.

The present invention

The above objects are fulfilled with the apparatus and method according to the present invention. The apparatus is defined by claim 1 and the method is defined by claim 13. The dependent claims disclose preferred embodiments of the invention.

The invention is a novel combination of purification techniques comprising essentially three steps. The water to be purified is passed through a series of reactors or chambers in a manner not allowing air or fumes to escape therefrom except at their respective outlet conduits. Air is passed through the same chambers but in a different sequence than the water.

One feature of the invention is the circulation of air in a loop where an air pump serves several purposes. The apparatus consists of 3 closed chambers or tanks where water and air can only enter and leave through sealed ports and pipes for such transport purposes. By "sealed" is understood that no air or odours are able to escape from the chambers to the environment except at the final outlet.

The raw wastewater enters the first chamber (chamber I) through a pipe with a water lock to prevent air from flowing back into the pipe. The water is typically filtered through a mesh or porous filter bag hanging from a rack in the first chamber to remove larger particles, such as hair. The water then either flows by gravity or it is pumped to the second chamber (chamber II). The second chamber is generally arranged as a biological treatment reactor incorporating suspended and/or attached microbiological cultures and a sedimentation zone to separate the culture from the liquid leaving the chamber. More typically the second chamber is arranged as a hybrid bioreactor combining the activated sludge principle and the biofilm principle, and consists of two zones. The water first enters a zone defined as the bioreactor and flows on to a separate zone for sedimentation of particles before it flows by gravity to the third chamber (chamber III). The particles separated by sedimentation consist mainly of bacteria grown on the organic matter to be removed from the water, and they are continuously transported back to the bioreactor zone. There is a water lock between the 2nd and the third chamber to prevent air from flowing with the water.

The third chamber consists of an adapted version of a conventional trickle filter. The adaptations are: 1. Air from the previous two chambers is introduced through a pipe in the underdrain in order

₅ to use the trickle filter as a filter to capture and biologically degrade the gasses and odours from the raw wastewater and the first treatment stages. 2. The trickle filter has an integrated flow equalisation measure to make the filter capable of handling the large load variations typical for "grey water" from recreation houses. The uniqueness of the invention is the way that the air is supplied from a single pump to serve several purposes in the described treatment process io consisting of 3 chambers.

The air is pumped through a conduit into the second chamber where it is introduced through diffusers into the bottom of vertical pipes in the interface between the two zones. Air bubbles rise vertically inside the pipes, termed risers, pulling along liquid from the bottom of the sedimentation zone to the bioreactor zone, supplying oxygen to the water and at the same time

I₅ pumping particles with active biomass from the sedimentation back to the bioreactor. This pumping action also supplies the required mixing of the bioreactor to keep the biomass suspended and in contact with the organic matter in the water to be removed by the biomass. This pumping action is designed so that it also pumps water from a level close to the top of the sedimentation zone to maintain a continuous vertical flow in the sedimentation zone to obtain a

20 more efficient sedimentation due to the interaction of particles to be separated, as known from the technology termed up-flow sludge beds. The air introduced in chamber Il has only one escape from this chamber and that is through a pipe to chamber I, where it flows through the chamber flushing out the air with the wastewater odours, and into a new pipe leading to the bottom of chamber III.

25 The air finally flows up through the filter in chamber III serving two new purposes. The air supplies oxygen to the biomass growing on the filter media so that an aerobic degradation of organic matter in the wastewater can occur. This air also contains odorous molecules flushed from chamber I and these molecules are adsorbed by the liquid and the biofilm, and aerobically degraded. The air is thereby cleaned before it is released through at pipe at the top of chamber III.

₃o Brief description of the figures

The invention is described with reference to the attached figures wherein:

Fig. 1 is an illustration the air and water flows through the complete 3 process chambers treatment plant Fig. 2 is an illustration of the hybrid bioreactor combining activated sludge, biofilm and up-flow sludge bed techniques operated with an air compressor

Fig. 3 is an illustration of the trickle filter with flow equalization, water and air treatment

Detailed description of the invention The following description is a description of preferred embodiments of the invention with reference to the enclosed drawings.

Referring to Figure 1, an embodiment of the entire apparatus and process of the invention is illustrated. The apparatus comprises 3 chambers where a single compressor or air pump or compressor 7a with two outlets 7b supplies air to the process, and serves several purposes in all three chambers. The air is pumped from the air compressor, 7a, situated outside the chambers through two conduits 7b into the second chamber where it is introduced through diffusers into the bottom of vertical pipes, supplying oxygen to the biological reaction, mixing liquid to keep the biomass suspended and supplying a pumping effect to transport biomass from a sedimentation zone back to a bioreactor zone, 4, (se also Fig. 2) and to maintain a vertical water flow in the sedimentation zone, 6. There is a water lock between the second and the third chamber to prevent air from flowing with the water. The air is therefore forced to flow from chamber II, through chamber I through conduit 7c to aerate this and to flush odorous gasses out from chamber I and into the bottom of chamber III through conduit 7d. The air flows up through chamber III, counter current to the wastewater, to supply oxygen to the biomass growing on the filter media so that an aerobic degradation of organic matter in the wastewater can occur. This air also contains odorous molecules flushed from chamber 1 and these molecules are adsorbed by the liquid and the biofilm, and aerobically degraded. The air is thereby cleaned before it is released through a pipe 7e at the top of chamber III. Chamber III houses a trickle filter with an integrated chamber for flow equalisation to increase the contact time between the water and the filter media (Figure 3).

The raw wastewater enters the first chamber through a pipe with a water lock 1 to prevent air from flowing back into the pipe. The water is filtered through a filter bag 2 hanging in the air from a rack in the first chamber, to remove larger particles, such as hair, to avoid clogging of the down stream processes. The filter bag 2 can be lifted out, emptied and put back in the same position. The filter bag needs to be emptied before it is full or clogged. The water either flows by gravity or it is pumped 3 to the second chamber.

The second chamber is a hybrid bioreactor combining the activated sludge principle, the sludge bed principle and the biofilm principle, and consists of two main zones. The water first enters a zone defined as the bioreactor 4 and flows on to a separate zone for sedimentation 6 of particles before it flows by gravity to the third chamber. The particles separated by sedimentation consist mainly of bacteria grown on the organic matter to be removed from the water, and they are continuously transported back to the bioreactor zone trough vertical pipes 5 termed risers, to obtain the activated sludge principle. The pumping action through the risers is obtained by air bubbles rising vertically inside the pipes 5 pulling along liquid from the bottom of the sedimentation zone to the top of the biofilm zone. The air bubbles also supply oxygen to the water and supply mixing of the bioreactor. Water is also pumped through a pipeline 13 from the upper part of the sedimentations zone 6 to the bottom of the risers 5 to maintain a vertical flow in the sedimentation zone 6 also when there is no water entering the treatment plant. This pumping action is also obtained by the air bubble induced vertical flow in the risers 5. This pumping action is designed so that the continuous vertical flow in the sedimentation zone 6 cause more efficient sedimentation due to the interaction of particles to be separated, as known from the technology termed up-flow sludge beds. Support media for biofilm growth 11 can also be positioned in the bioreactor zone 4 to further enhance the accumulation of organisms involved in the water treatment.

The third chamber consists of an adapted version of a conventional trickle filter. The adaptations are: 1. Air from the previous two chambers is introduced through a pipe in the underdrain in order to use the trickle filter as a filter to capture and biologically degrade the gasses and odours from the raw wastewater and the first treatment stages. 2. The trickle filter has an integrated flow equalisation measure to make the filter capable of handling the large load variations typical for "grey water" from recreation houses.

The trickle filter (Fig.3) function as a biological filter where wastewater inlet and air outlet is at the top, water flow by gravity from the top trough an inert trickle filter media 9 with large surface area to volume ratio, such as expanded clay, sand, gravel, plastic media, on which bacteria and other living organisms live, capture and degrade pollutants. One or more equalisation tank(s) 8 is (are) integrated in the trickle filter medium. The watertight tank(s) is (are) positioned within the bio filter to obtain flow equalisation. Flow equalisation is to slow down the flow of wastewater to be treated, which typically comes in bursts, to increase the contact time between the water and the biofilm culture treating it. The tank or basin is lined on the inside and the outside by a cloth 14 capable of transporting water so that it will drain slowly after it has been filled, to cause slow drainage of the tanks during periods of low or no load to the treatment process, supplying moisture to the biofilm on the filter medium. The equalisation tank may also be fitted with several small holes to obtain faster drainage, when suitable. More than one equalisation basins may be applied within a single trickle filter. Air from chamber 1 flows through the media from the bottom to the top to supply oxygen to the biological processes and to deposit odorous chemical from chamber I to the liquid. The treated water flow by gravity from the trickle filter, to a filter medium support, air inlet and underdrain structure at the bottom 10 to an outlet pipe. Example

Full-scale pilot plants have been tested on vacation homes. Water samples were taken from the inlets and from the outlets of the chambers. The samples were analysed for organic matter and nutrient content. Samples from the retained particles in the filter bag were analysed for solids and organic matter content. The treatment effect increased rapidly after start-up and reached a maximum when the culture was well established after 1 month. The quality of the treated water was in accordance with standard demands; below discharge concentration limits. The water quality was similar to that obtained in alternative established treatment plant solutions. The cost of the pilot plants were less than half of any known treatment plants for the same purpose on the Norwegian market. The pre treatment filter bag removed ca. 40 % of the total solids in the wastewater. The organic fraction of this, measured as volatile solids, was approximately 60 %, implying that the removal of organic matter was approximately 50 % in the filter bag.

Ca. 70 % of the organic matter entering chamber Il was removed from the wastewater through chambers Il and III. The total removal of organic matter through the pilot plants was therefore ca. 80 %. The phosphate removal was above 50 % and the effluent concentration below 0.5 mgP/1. Total nitrogen removal was ca 30 % and the effluent concentration below 1 mgN/l. Most of the odours smelled in chamber I was removed in chamber 111 producing an almost odourless and nuisance free air outlet.

With reference to Figure 1, the apparatus consists of 3 closed chambers where water and air can only enter and leave the chambers through ports and pipes for such transport purposes: Double line illustrate water flow ducts and single line arrow illustrate ducts for air flow. The raw wastewater enters the first chamber through a pipe 3a with a water lock 1 to prevent air from flowing back into the pipe. The water is filtered through a mesh or a filter bag 2 hanging in the air from a rack in the first chamber to remove larger particles, such as hair, to be emptied at regular intervals or as required. The water then either flows by gravity or it is pumped to the next chamber by a pump 3b through a conduit 3c. The second chamber is a hybrid bioreactor combining the activated sludge principle and the biofilm principle, and consists of two zones. The water first enters a zone defined as the bioreactor 4 and flows on to a separate zone 6 for sedimentation of particles, before it flows by gravity through a pipe 3d with a water lock to the third and final chamber. The air is pumped by a compressor or air pump 7 from the outside through a duct into the bottom of vertical pipes 5 termed risers, pulling along liquid from the bottom of the risers and out at the top. Chamber III houses of a trickle filter 9 with a flow equalization tank, or tanks, 8 and an underdrain 10 at the bottom. A flow equalization tank can also serve as a water lock to prevent air from flowing from chamber 11 to III directly.

We are now referring to Figure 2. Chamber Il consists of the components 4, 5, 6 shown in Figure 1 and the following elements: Diffusers 12 at the bottom of the risers 5 to make the air from the two lines from the compressor 7 enter the water as small bubbles. The risers 5 are pipes with open tops and bottoms so that the rising air bubbles pull water along, creating a water flow from the bottom of the bioreactor zone 4 and the sedimentation zone 6 to the top of the bioreactor zone. Sludge with active biomass separated by gravity in the sedimentation zone is thereby returned to the bioreactor zone 4 creating an "activated sludge process". A pipe 13 with an opening in the upper part of the sedimentation zone 6 and the other open end at the bottom of one of the risers 5 is included to obtain a flow from the upper part of the sedimentations zone 6 via the pipe 13 and the riser 5 to the bioreactor zone 4 to obtain a continuous vertical flow in the sedimentation zone 6 to obtain a more efficient sedimentation due to the interaction of particles to be separated, as known from the technology termed "up-flow sludge beds". The bioreactor zone is also equipped with a medium with large surface area 11 serving as substratum for fixed growth of biomass, termed "biofilm", adsorbing and degrading the pollutants in the water. Double lines illustrate water flow ducts 3c and 3d and single line arrows illustrate ducts for air flow.

We are now referring to Figure 3. Chamber III consists of the components 8, 9, 10 shown in Figure 1 and a cloth 14 covering the equalization tank 8. The cloth 14 serves the purpose as a wicket to spread water from the inlet pipe to the filter medium 9 and to keep 9 moist during periods when no wastewater enters the system, to maintain a healthy biofilm culture on the medium. More than one equalization tank can be used. The air from chamber I enters the bottom of chamber III, flowing up through the medium 9 supplying oxygen and odorous molecules flushed from chamber I to the biofilm, aerobically degrading this and pollution left in the effluent from chamber II. The water outlet 3e at the bottom includes a water lock to prevent air outflow, forcing the air up through the filter medium 9.

Claims

oClaims

1. Apparatus for purification of waste water comprising three integrated and substantially closed chambers (I, II, III) of which the first chamber (I) is one for separation of coarse waste, as well as comprising means for supply of the water to be purified and means for supply of air, characterized in that the second chamber (II) is arranged as a biological treatment reactor (4) incorporating suspended and/or attached microbiological cultures and a sedimentation zone (6) to separate the culture from the liquid leaving the chamber, while the third chamber (111) comprises a trickle filter (9) arranged to biologically purify the discharge air as well as the discharge liquid.

2. Apparatus as claimed in claim 1, characterized in that the microbiological culture present in a form chosen among suspended microbiological cultures, attached microbiological cultures and a combination thereof.

3. Apparatus as claimed in claim 1, characterized in that chamber (II) is arranged as an activated sludge reactor, implying that the culture separates from the liquid leaving the chamber in a sedimentation zone is returned to the reaction zone.

4. Apparatus as claimed in claim 1, characterized in that chamber (H) is arranged as a biofilm reactor.

5. Apparatus as claimed in claim 1, characterized in that chamber (II) is arranged as a combination of a biofilm reactor and an activated sludge reactor.

6. Apparatus as claimed in claim 1, characterized in that the water is arranged to pass in sealed passages (3a-3e) to a first chamber (I), from first chamber (I) to a second chamber (II), and from second chamber (II) to a third chamber (III) and eventually to be discharged in a purified condition.

7. Apparatus as claimed in claim 1, characterized in that the apparatus is arranged to receive air being blown (7) into second chamber (II) for allowing purification according to the activated sludge principle.

8. Apparatus as claimed in claim 1, characterized in that second chamber (II) is arranged for internal recirculation of material between a first biofilm zone (4) and a second sedimentation zone (6), using air as a driving medium for such recirculation.

9. Apparatus as claimed in claim 8, characterized in that the apparatus comprises means (7a, 7b) for blowing air into the lower end of the sedimentation zone for thereby initiating an internal circulation therein independent of water supply, and to act as a transportation medium for settled particles from the sedimentation zone to the biofilm zone.

10. Apparatus as claimed in claim 1, characterized in that the air is arranged to pass first to second chamber (ll)(7b), from second chamber (II) to first chamber (l)(7c), from first chamber (I) to third chamber (III) (7d) and eventually to be released in a mainly pure condition (7e).

11. Apparatus as claimed in claim 1, characterized in that the air is arranged to pass counter- current with the liquid in third chamber (III).

12. Apparatus as claimed in claim 1, characterized in that the third chamber (III) comprises at least one equalisation tank (8) arranged to receive entering liquid () from second chamber and to allow said liquid to pass through the trickle filter at a suitable volume rate.

13. Apparatus as claimed in claim 12, characterized in that the equalisation tank (8) is furnished with a wick device which prevents the tank from drying out when the apparatus is left unused.

14. Apparatus as claimed in claim 1, characterized in that one single pump (compressor) is arranged to pump the required volume rate of air into second chamber (II) of the apparatus and further on through the apparatus.

15. Apparatus as claimed in claim 1, characterized in that it comprises a water seal arranged to prevent odours from first chamber (I) to escape to the environment.

16. Apparatus as claimed in claim 1, characterized in that it comprises a pump for transportation of water from first to second chamber (II).

17. Method for purification of waste water, characterized in the combination of the following purification steps:

- a first separation of coarse particles and fibres in a conventional coarse filter,

- a second separation and conversion step constituting a biological treatment incorporating suspended and/or attached microbiological cultures and a sedimentation zone to separate the culture from the liquid leaving the second separation step, and

- a third separation and conversion step in the form of a trickle filter.