FORM-2 THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2006
COMPLETE
Specification
(See Section 10 and Rule 13)


COMPACT SMALL SCALE HYBIRD BIOFILTER FOR SEWAGE TREATMENT
THERMAX LIMITED

an Indian Company
of D-13, MIDC, Chinchwad,
Pune - 19, India
The following specification particularly describes the invention and the manner in which it is to be performed.


FIELD OF THE INVENTION
The present invention relates to sewage treatment.
Particularly, the present invention relates to sewage treatment using biofilter.
BACKGROUND OF THE INVENTION & PRIOR ART
Large volume of sewage is generated everyday from residential, industrial, institutional and commercial establishments. Treatment for sewage is required to make it suitable for disposal into a river, stream or the ocean or for the purpose of recycling and reuse. Sewage is generally treated through physical, chemical and biological processes, to remove/bring down the organic and inorganic impurities, within or below the respective specified standards. Conventionally, sewage treatment includes a pretreatment for removal of inert material, a primary treatment including a sedimentation stage, a secondary treatment for removal of the organic matter, a tertiary treatment for further improving the effluent quality and an effluent polishing stage including disinfection and filtering for further purification of the effluent.
Any sewage treatment system along with the treated water effluent also generates biological sludge (solid or semi-solid waste) which is either disposed off in a landfill or incinerated or goes through a separate anaerobic or aerobic sludge digestion system for further treatment and volume reduction. This leads to separate processes for organic removal and sludge digestion through additional energy input and high foot print area. This finally leads to high capital investment and high operating cost. Disposal of sludge is another matter of concern in wastewater treatment facilities because of high costs and lack of space.
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The existing pollution control norms require the industries, institutions and commercial establishments to install sewage treatment facilities to meet the statutory requirements. In small-scale industries like dairy farm, animal husbandry and food processing units and commercial establishments like hotels and restaurants, where the amount of sewage generated is less and mainly organic in nature; a small sewage treatment plant for wastewater treatment is required to make the sewage suitable for disposal into the sewer. In such cases, the primary requirement of a sewage treatment facility is a small foot print area, low initial investment, low operating and maintenance costs and reduction in quantity of sludge produced. Thus, there is a requirement for a compact small-scale sewage treatment plant that is cost-effective, easy to operate and produces less sludge.
The secondary treatment unit of a conventional sewage treatment facility is designed to substantially reduce the organic content of the sewage through the aerobic biological processes broadly classified as fixed-film e.g. trickling filters and suspended-growth e.g. activated sludge process. These processes require a source of air or oxygen to perform the reactions. For this purpose, external aeration devices are required, which further increases the capital and operating cost of the unit.
Various attempts have been made to provide a compact system for sewage treatment that requires a small foot-print area, involves less capital investment and reduces the cost of operation and maintenance.
Patent No: WO2007/050775, discloses a system and method for wastewater treatment using a biological reactor. The system disclosed in WO2007/050775 consists of three units: a primary clarifier located before the bioreactor, a fixed-
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film bioreactor and another clarifier located after the bioreactor. The bioreactor is provided with aeration devices, mixing devices and control sensors. The control sensors are provided on the bioreactor for monitoring parameters like pH, temperature, time and concentrations. The cited system however does not have provisions for sludge treatment or digestion. The cited system involves high operating and maintenance costs because of the aeration, mixing and sensing devices and requires large foot-print area.
Patent No: WO2008/155407, discloses a single unit for wastewater treatment. The unit disclosed in WO2008/155407 comprises: an upper chamber which is a biofilter, an air distribution unit located below the biofilter and a sludge collecting chamber as the bottom chamber. The air distribution unit provides aeration to the sludge collecting chamber. The cited unit does have provisions for sludge recycling or treatment or digestion and requires external aeration devices.
JP Patent No: 60102994, discloses an apparatus and method for cleaning and deodorizing sewage. The cited method consists of a two-chambered tower provided with an upper trickling bed filter and bottom aerating tank. The method involves sprinkling the sewage through a packed bed trickling filter and then allowing it to flow into the contact aerating tank provided below the trickling filter. The apparatus uses diffuser pipes and external air supply to remove the odor produced from the sewage sprinkling pipes. The apparatus also requires external aeration devices for providing aeration to the contact tank. The method cited in JP 60102994 does not have provisions for sludge treatment and requires a high energy input.
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GB Patent No: 2239237, discloses a compact trickling filter apparatus for treating sewage, applicable only in small communities. The cited apparatus comprises a single unit provided with a primary settlement tank and a secondary settlement tank located side-by-side at the bottom of the unit, pump means and a trickling filter tank located in the upper portion of the unit. Aeration is provided in the filter tank by natural air convection. The apparatus cited in GB 2239237 however provides only a one-stage treatment for sewage, making the apparatus unlikely for applications where the sewage has a high Biological Oxygen Demand (BOD) content. The apparatus also does not provide any treatment or digestion to the sludge generated.
KR Patent No: 4012322, discloses a compact size apparatus for water treatment that requires small area for installation and reduces operation cost. The cited apparatus consists of a single unit provided with a bio-reaction part and a filtration part. The filtration part is provided with a first filter that consists of a sieve screen and a second filter that consists of an air blowing tank and air venting hole. The treatment primarily occurs in the first bio-reaction part which consists of an inner anaerobic zone and an outer aerobic zone. The apparatus cited in KR 4012322, does not have provisions for handling the sludge that is generated during the process. Other limitation of the above cited apparatus include choking that could be caused in the filtration part during the operation.
CN Patent 1502569, discloses a system for wastewater treatment that comprises a biological filter in the upper portion and a oxidation tank in the lower portion. The above cited system is placed horizontal on the ground wherein the upper and lower portions are divided by a water-collecting plate. In the cited system, raw sewage enters the bio filter from the top through sewage inlet lines and is provided with an
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external air supply, external aeration devices are also required in the lower portion. The effluent from the filter gets collected into the water-collecting tank and is then sent to the oxidation tank from the side. The system cited in CN 1502569 requires a large foot print area and high energy input for the continuous aeration of both the chambers.
The aforesaid attempts have several limitations that can be summarized as below:
a. Most of the compact apparatus for sewage treatment provide only a one-
stage treatment to the sewage, thus, making them inapt for wastewater
containing high BOD. Thus, there is a need for a compact apparatus for
sewage treatment that provides primary, secondary and tertiary treatment.
b. Sludge treatment is vital because of the high cost and stringent disposal
regulations; therefore, there is a need for a compact sewage treatment unit
with provisions for sludge treatment or digestion.
c. There is need for a sewage treatment unit that is sustainable and
environmental friendly.
OBJECTS OF THE INVENTION
An object of this invention is to provide a system for treating municipal sewage.
Another object of this invention is to provide a system for treating organic wastewater.
Still another object of this invention is to provide a system for treating sewage which is compact and uses a small foot print area.
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Yet another object of this invention is to provide a system for treating sewage which requires less capital investment.
One more object of this invention is to provide a system for treating sewage which is easy to operate, requires low maintenance, reduces the operating cost and produces minimal disposable waste.
Still one more object of this invention is to provide a system for treating sewage which consumes less energy.
Yet one more object of this invention is to provide a system for treating sewage which is sustainable and environmental friendly.
SUMMARY OF THE INVENTION
In accordance with the preferred embodiment of the present invention, a compact sewage treatment system is provided for treating organic wastewater, said system comprising:
• an upper chamber comprising:
a. a biofilter; and
b. a effluent collecting hopper provided below said biofilter, in the
operative configuration of said system;
• a lower chamber provided below said upper chamber, in the operative
configuration of said system, said lower chamber comprising:
a. an aerobic sludge digestion section having a treated water
discharge outlet;
b. a sludge holding unit located below said aerobic sludge digestion
section; and
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c. a sludge discharge outlet from said sludge holding unit;
• conduit means leading from said effluent collecting hopper in said upper chamber to said sludge digestion section in said lower chamber opening in proximity to said sludge holding unit;
• pipe means connected at one end to said sludge discharge outlet and other end opening above said upper chamber to receive and lead a mixture of raw sewage and sludge to said upper chamber; and
• pump means adapted to circulate the mixture of raw sewage and slurry containing sludge through said pipe means to said upper chamber.
Typically, in accordance with this invention, said biofilter is a trickling bed filter provided with a fixed-film attached growth system.
Typically, in accordance with this invention, inclined baffles are provided in said treated water discharge outlet to prevent sludge particles from escaping through said treated water discharge outlet.
Typically, in accordance with this invention, said sludge holding unit is in the form of a hollow frustum of an inverted cone having tapering side walls and said sludge holding unit is provided with an additional sludge discharge outlet for removal of excess sludge.
Typically, in accordance with this invention, said conduit means are provided at the operative bottom of said effluent collecting hopper.
Typically, in accordance with this invention, said conduit means comprise a plurality of pipes at least some of which are inclined.
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Typically, in accordance with this invention, a flow distribution assembly is located above said upper chamber.
Typically, in accordance with this invention, a shell is provided to encase the system.
Typically, in accordance with this invention, said system includes a pretreatment unit consisting of a screen for removing inert matter from raw sewage.
Typically, in accordance with this invention, a method for treatment of sewage, said method comprising the following steps:
• spraying a mixture of raw sewage and slurry containing sludge through a biofilter loaded with immobilized microorganisms attached to a biofilm;
• collecting treated water and sludge operatively below said biofilter;
• discharging the treated water and sludge in a lower chamber where the treated water and sludge are separated while continuing with sewage digestion;
• allowing the sludge to settle in a sludge holding unit while treated water rises through a treated water discharge outlet having inclined baffles;
• discharging treated water and sludge from said lower chamber separately;
• feeding raw sewage to said discharge sludge for iteration of the said process; and
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• disposing a decided amount of sludge periodically through an additional sludge discharge outlet.
Typically, in accordance with this invention, the raw sewage is screened to remove inert matter and stored in a storage tank before feeding to said discharge sludge.
Typically, in accordance with this invention, aeration is provided in said lower chamber by the venturi effects that are generated when effluent flows from said upper chamber to said lower chamber.
Typically, in accordance with this invention, the ratio of raw sewage to slurry containing sludge entering said biofilter is between 1: 10 to 1:25.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The invention will now be described with the help of the accompanying drawings, in which,
FIGURE 1 illustrates the complete schematic diagram of the system, in accordance with the present invention;
FIGURE 2 illustrates a pictorial diagram of the system from front and top view, in accordance with the present invention;
FIGURE 3 illustrates a pictorial diagram of the system showing the sectional side-view, in accordance with the present invention;
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FIGURE 4 illustrates a pictorial diagram of the system from the front view and showing the sectional-top view of the sludge holding unit, in accordance with the present invention;
FIGURE 5 illustrates the effluent collecting hopper and conduit means from top, front and section views, in accordance with the present invention; and
FIGURE 6 illustrates the sludge holding unit from top and front view and a brocken view of the inclined baffles located in treated water discharge outlet, in accordance with the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The invention will now be described with reference to the embodiments shown in the accompanying drawings and the embodiment does not limit the scope and ambit of the invention. The description relates purely to the exemplary preferred embodiment of the invention and its suggested application.
The present invention envisages a compact sewage treatment system for treating organic wastewater and a method thereof. The apparatus consists of a single unit divided into an upper chamber and a lower chamber in which a two-stage treatment is provided.
FIGURE 1 illustrates the complete schematic diagram of the system in accordance with the present invention and is represented by the numeral 100.
In accordance with a preferred embodiment of the present invention, the system 100 includes the following: an upper chamber 102 comprising a biofilter 106
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which is a trickling bed filter provided with a fixed-film attached growth system and a effluent collecting hopper 108 provided below said biofilter 106, in the operative configuration of said system 100 for collecting the water that trickles from said biofilter 106; a lower chamber 104 provided below said upper chamber 102, in the operative configuration of said system 100, said lower chamber 104 comprising an aerobic sludge digestion section 110 for farther treating the sewage and sludge having a treated water discharge outlet 112 provided at the top side for discharging the treated effluent, a sludge holding unit 114 located below said aerobic sludge digestion section 110 for holding sludge and a sludge discharge outlet 116 from said sludge holding unit 114 for removing the sludge for recycling; conduit means 118 leading from said effluent collecting hopper 108 in said upper chamber 102 to said sludge digestion section 110 in said lower chamber 104 for carrying the sewage and sludge to the lower chamber 104 opening in proximity to said sludge holding unit 114; pipe means 120 connected at one end to said sludge discharge outlet 116 and other end opening above said upper chamber 102 to receive and lead a mixture of raw sewage and slurry containing sludge to said upper chamber 102; and pump means 124 adapted to circulate the mixture of raw sewage and slurry containing sludge through said pipe means 120 to said upper chamber 102. The pipe means 120 are provided with an inlet for receiving raw sewage 122, the inlet is located between said sludge discharge outlet 116 and said pump means 124 for the purpose of mixing raw sewage and slurry containing sludge before pumping to said biofilter 106; a flow distribution assembly 126 is provided on said other end of said pipe means 120 opening above said upper chamber 102 for spraying a mixture of raw sewage and slurry containing sludge to the upper chamber 102. A pretreatment unit consisting of a screen 130 for removing inert matter from raw sewage and a storage tank 128 are provided before said system.
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FIGURE 2 illustrates a pictorial diagram of the system from front and top view, in accordance with the present invention and is represented by the numeral 200.
In accordance with a preferred embodiment of the present invention, said diagram 200 illustrates said system from a front view 202 and a top view 204. The system is provided with inclined baffles 206 in said treated water discharge outlet 112 to prevent the sludge particles from escaping through said treated water discharge outlet 112. The sludge holding unit 114 is in the form of a hollow frustum of an inverted cone having tapering side walls where the sludge is allowed to settle after digestion in the sludge digestion section 110. The sludge holding unit 114 is provided with a sludge discharge outlet 116 for discharging sludge for recycling and also an additional sludge discharge outlet 208 for removal of excess sludge. The conduit means 118 are provided at the operative bottom 210 of said effluent collecting hopper 108 for carrying the raw sewage and slurry containing sludge to said lower chamber 104. A section S-S passes through the centre-line of the diagram seen in 200.
FIGURE 3 illustrates a pictorial diagram of the system showing the sectional side-view, in accordance with the present invention and is represented by the numeral 300.
In accordance with a preferred embodiment of the present invention, said diagram 300 illustrates said system from the side-view through section S-S showing said aerobic sludge digestion section 110 and said conduit means 118. The conduit means 118 which are provided at the operative bottom 210 of the effluent collecting hopper 108 comprise a plurality of pipes 304 at least some of which are inclined.
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FIGURE 4 illustrates a pictorial diagram of the system from the front view and showing the sectional-top view of the sludge holding unit, in accordance with the present invention and is represented by the numeral 400.
In accordance with a preferred embodiment of the present invention, said diagram 400 illustrates the said system from front view 402 and sectional view through section H-H showing the top view 404 of said sludge holding unit 114. A shell 406 is provided to encase said system.
FIGURE 5 illustrates the effluent collecting hopper and conduit means from top, front and section views, in accordance with the present invention and is represented by the numeral 500.
In accordance with a preferred embodiment of the present invention, the Fig. 5 illustrates a top view 502, front view 504 and sectional view through section Q-Q 506 of the effluent collecting hopper 108 and conduit means 118; and top view 508 of the operative bottom 210 of the effluent collecting hopper 108 showing the opening of the conduit means 118.
FIGURE 6 illustrates the sludge holding unit from top and front view and a brocken view of the inclined baffles located in the treated water discharge outlet, in accordance with the present invention and are represented by the numeral 600.
In accordance with a preferred embodiment of the present invention, Fig. 6 illustrates a top view and front view 602 of said sludge holding unit 114, a brocken view 604 of said inclined baffles 206 located in said treated water discharge outlet
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112 and a top view 606 of the bottom of said sludge holding unit showing the sludge discharge outlet 116.
A method for treatment of sewage comprising the following steps: A mixture of raw sewage and slurry containing sludge is sprayed through a biofilter 106 loaded with immobilized microorganisms attached to a biofilm. The treated water and sludge flowing down from said biofilter 106 is collected operatively below said biofilter 106 in a effluent collecting hopper 108. The treated water and sludge is then discharged in a lower chamber 104 consisting of a sludge digestion section 110. In the sludge digestion section 110, the treated water and sludge are separated while continuing with sewage digestion. The sludge is allowed to settle in a sludge holding unit 114 while treated water rises through a treated water discharge outlet 112 having inclined baffles 206. The treated water and sludge is discharged separately from said lower chamber 104 through the treated water discharge outlet 112 and sludge discharge outlet 116, respectively. The raw sewage is fed to said discharge sludge for iteration of the said process. Periodically, a decided amount of sludge is disposed from an additional sludge discharge outlet 208. The raw sewage is sent through a pretreatment unit 130 where it is screened to remove the inert matter and stored in a storage tank 128 before feeding to said discharge sludge. Aeration is provided in said lower chamber 104 by the venturi effects that are generated when the treated water and sludge flow from said upper chamber 102 to said lower chamber 104 through the conduit means 118. Oxygen is dissolved in water when the water trickles down said biofilter 106 and air is absorbed by said water when it passes through said conduit means 118, thus, producing aeration in said sludge digestion section 110. The ratio of raw sewage to slurry containing sludge entering said biofilter 106 is between 1: 10 to 1:25.
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The treated water discharged from said treated water discharge outlet 112 consists of 25-50 ppm of sludge. This treated water is suitable for reuse in gardening, washing, cleaning and landscaping. Post treatment could be provided to further purify the water. The treated water from said treated water discharge outlet 112 can be passed through a chlorine contact tank for disinfection. The disinfected water can be further purified by passing through a dual-media sand filter and activated carbon bed.
EXPERIMENTAL DATA
1. The compact sewage treatment system of present invention was used to treat
15 m3/d of domestic sewage with an inlet Biological Oxygen Demand
(BOD) of up to 250 mg/1, inlet Chemical Oxygen Demand (COD) of up to
500 mg/1 and inlet Total Suspended Solids (TSS) of up to 235 mg/1. After
treatment, a BOD reduction of approximately 95% was achieved, the COD
was reduced by 85-90% and the TSS was reduced by 87-90%.
2, The system of present invention was used in a sewage treatment plant for
treating municipal sewage of capacity 7-10 m3/d. The inlet BOD varied from
150-220 mg/1, after treatment the BOD was reduced to 15-28 mg/1, thus, by
using the system a BOD reduction of approximately 90% was achieved. The
Total Dissolved Solids (TDS), Total Suspended Solids (TSS), Total Kjeldhal
Nitrogen (TKN) and Total Phosphates were also significantly reduced.
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TECHNICAL ADVANCEMENT
A system for treating organic wastewater is provided, as described in this invention has several technical advantages including but not limited to the realization of:
• a system for treating sewage which is compact and uses a small foot print area;
• a system for treating sewage which requires less capital investment;
• a system for treating sewage which is easy to operate, requires low maintenance, reduces the operating cost and produces minimal disposable waste;
• a system for treating sewage which consumes less energy; and
• a system for treating sewage which is sustainable and environmental friendly.
In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only. While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principle of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.
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We claim:
1. A compact sewage treatment system for treating organic wastewater, said system comprising:
• an upper chamber comprising:
c. a biofilter; and
d. a effluent collecting hopper provided below said biofilter, in the
operative configuration of said system;
• a lower chamber provided below said upper chamber, in the operative
configuration of said system, said lower chamber comprising:
d. an aerobic sludge digestion section having a treated water
discharge outlet;
e. a sludge holding unit located below said aerobic sludge digestion
section; and
f. a sludge discharge outlet from said sludge holding unit;
• conduit means leading from said effluent collecting hopper in said upper chamber to said sludge digestion section in said lower chamber opening in proximity to said sludge holding unit;
• pipe means connected at one end to said sludge discharge outlet and other end opening above said upper chamber to receive and lead a mixture of raw sewage and slurry containing sludge to said upper chamber; and
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• pump means adapted to circulate the mixture of raw sewage and slurry containing sludge through said pipe means to said upper chamber.
2. A system as claimed in claim (1), wherein said biofilter is a trickling bed filter provided with a fixed-film attached growth system.
3. A system as claimed in claim (1), wherein inclined baffles are provided in said treated water discharge outlet to prevent sludge particles from escaping through said treated water discharge outlet.
4. A system as claimed in claim (1), wherein said sludge holding unit is in the form of a hollow frustum of an inverted cone having tapering side walls and said sludge holding unit is provided with an additional sludge discharge outlet for removal of excess sludge.
5. A system as claimed in claim (1), wherein said conduit means are provided at the operative bottom of said effluent collecting hopper.
6. A system as claimed in claim (6), wherein said conduit means comprise a plurality of pipes at least some of which are inclined.
7. A system as claimed in claim (1), wherein a flow distribution assembly is located above said upper chamber.
8. A system as claimed in claim (1), wherein a shell is provided to encase the system.
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9. A system as claimed in claim (1), wherein said system includes a pretreatment unit consisting of a screen for removing inert matter from raw sewage.
10. A method for treatment of sewage, said method comprising the following steps:

• spraying a mixture of raw sewage and slurry containing sludge through a biofilter loaded with immobilized microorganisms attached to a biofilm;
• collecting treated water and sludge operatively below said biofilter;
• discharging the treated water and sludge in a lower chamber where the treated water and sludge are separated while continuing with sewage digestion;
• allowing the sludge to settle in a sludge holding unit while treated water rises through a treated water discharge outlet having inclined baffles;
• discharging treated water and sludge from said lower chamber separately;
• feeding raw sewage to said discharge sludge for iteration of the said process; and
• disposing a decided amount of sludge periodically through an additional sludge discharge outlet.
11 .A method as claimed in claim (10), wherein raw sewage is screened to remove inert matter and stored in a storage tank before feeding to said biofilter along with slurry containing sludge.
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12.A method as claimed in claim (10), wherein aeration is provided in said lower chamber by the venturi effects that are generated when the treated water and sludge flows from said upper chamber to said lower chamber.
13.A method as claimed in claim (10), wherein the ratio of raw sewage to slurry containing sludge entering said biofilter is between 1: 10 to 1:25.