DESC:DECENTRALIZED WASTEWATER MANAGEMENT SYSTEM
Field of invention
The present invention is generally related to wastewater management and more particularly it is related to a decentralized system for wastewater management for recycle and reuse of wastewater at source.
Background of the invention
In India, centralized plants are a common norm wherein sewage or domestic wastewater of a town or city is collected at one place which needs sewage transfer network, needs huge infrastructure and capital. More-over, the treated water can if needed to be reused, needs pumping energy. This centralized system requires huge lands which makes land acquisition a task for the government and even the land availability is a challenge. The centralized waste water management systems are neither modular nor movable. As such, wastewater is required to be transported to the system. Transport of wastewater from one place to another makes the need of sewage transport network an important factor and it needs huge capital as well. Further, recycling and reusing treated wastewater from a centralized plant needs additional energy or money. Centralized wastewater management systems normally face all these challenges.
Accordingly there exists a need to provide a system to treat, recycle and reuse the wastewater at source with no need to transport sewage from one place to another, that will overcome the deficiencies of prior art.
Objects of the invention
Object of the present invention is to provide a system to treat, recycle and reuse the wastewater at source.
Another object of the present invention is to provide a wastewater management system that will eliminate the need of transport of sewage/ wastewater from one place to another.
Still another object of the present invention is to provide a system for wastewater management which has least possible foot-print and power consumption.
Yet another object of the present invention is to provide a system for wastewater management having reduced sludge generation
Summary of the invention
The present invention provides a decentralized wastewater management system comprising an equalization tank, a biozone tank, a settling tank, a sludge holding tank, a chlorine contact tank and a sand filter mounted on a single platform. The equalization tank is fitted with a screening unit and a sewage transfer pump, wherein the wastewater is received into the equalization tank through an inlet pipe fitted thereto and passed through the screening unit for removal of solids. In an embodiment, the screening unit has mesh screens of varying sizes optimized for solids removal. The biozone tank receiving pre-treated wastewater from the equalization tank is fitted with at least one air blower for aeration of the pretreated water. The biozone tank is having a plurality of fixed media units stacked tightly therein to a height and width to provide a surface area and volume sufficient for growth of biomass for complete nitrification of ammoniacal nitrogen. In an embodiment, the fixed media units from the plurality of fixed media units are structured units made up of FRP material. The settling tank is receiving the biomass liquor from the biozone tank wherein suspended solids separated from the biomass liquor are allowed to settle at the bottom under the influence of gravity to form a sludge that is received in the sludge holding tank while a clear supernatant water is further treated in the chlorine contact tank and the sand filter for chlorine treatment and sand filtration thereby forming a filtered clear water.

Brief description of the drawings:
The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1 shows a decentralized wastewater management system in accordance with embodiment of the present invention;
Figure 2A and 2B show layouts of decentralized wastewater management system in accordance with embodiments of the present invention; and
Figure 3 shows a perspective view of fixed media unit used in biozone of the decentralized wastewater management system in accordance with the present invention.
Detailed description of the invention
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiments.
The present invention provides a de-centralized waste water management system that solves local body problems related to waste water discharge and treatment, health and sanitation and budget allocation. In the system, the raw sewage collected in a raw sewage sump and first screened and pretreated and then passed through a biological treatment zone and finally through a tertiary treatment zone. In the system, the small capacity units built in mild steel epoxy painting are used which have least possible foot-print and power consumption. Sludge generation in the system is reduced to its lowest as yield is just 10% meaning only 10% of BOD load is converted into sludge volume with 1% consistency.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description and in the table below.
Table:
Ref No: Component Ref No: Component
2 Inlet valve 40 Sludge holding tank
4 Screening unit 50 Chlorine contact tank
6 Sewage transfer pump 60 Chlorine dosing unit
10 Equalization tank 65 Filter Feed pump
15 Air blower 70 Sand filter
20 Biozone tank 75 Drain
25 Fixed media units 80 Product water tank
30 Settling tank/ Tube settler
Referring to the figures 1 to 3, a decentralized wastewater management system (100) (herein after referred to as “the system (100)”), in accordance with the present invention is shown. The system (100) comprises of a pre-treatment zone (A), a biological treatment zone (B) and a tertiary treatment zone (C) mounted on a single platform.
The pretreatment zone (A) consists of an equalization tank (10) fitted with a screening unit (4) and a sewage transfer pump (6). The raw wastewater is received in the equalization tank (10) through an inlet pipe fitted with an inlet valve (2). Pre-treatment removes all materials that can be easily collected from the raw sewage before they damage or clog the pumps and sewage lines of primary treatment clarifiers. Objects that are commonly removed during pre-treatment include trash, tree limbs, leaves, branches, and other large objects. The influent in sewage water passes through the screening unit (4) to remove all large objects like cans, rags, sticks, plastic packets etc. carried in the sewage stream. The solids are collected and later disposed in a landfill, or incinerated. The screening unit (4) has bar screens or mesh screens of varying sizes optimized for solids removal. If gross solids are not removed, they become entrained in pipes and moving parts of the treatment plant, and can cause substantial damage and inefficiency in the process. The solids are collected and later disposed in a landfill, or incinerated. The sewage transfer pump (6) pumps the pre-treated wastewater to the biological treatment zone (B)
The biological treatment zone (B) consists of a biozone tank (20), a settling tank (30) and a sludge holding tank (40). The pre-treated wastewater from the equalization tank (10) is received in the biozone tank (20) fitted with at least one air blower (15). The biozone tank (20) is having a plurality of fixed media units (25) fitted therein tightly.
The purpose of the biological treatment zone (B) is the further treatment of the pre-treated wastewater to remove the residual organics and suspended solids. The biological treatment zone (B) involves the removal of biodegradable dissolved and colloidal organic matter using aerobic biological treatment processes performed in the presence of oxygen by aerobic microorganisms that metabolize the organic matter in the wastewater, thereby producing more microorganisms and inorganic end-products (principally CO2, NH3, and H2O). After the primary treatment, greater part of BOD remaining in the sewage is in the form of dissolved organic matter. BOD is a measure of the amount of oxygen required to remove waste organic matter from water in the process of decomposition by aerobic bacteria. The biological treatment zone (B) is designed to substantially degrade the biological content of the sewage which is derived from human waste, organic matter, food waste, soaps and detergent. The biological treatment of BOD and complete nitrification of ammoniacal nitrogen takes place in the biozone tank (20). This process consists of growth of different bacteria/ micro-organism on the fixed media (25). Microbiological growth occurs by utilizing organic compounds and ammoniacal nitrogen. The micro-organisms absorb and oxidize organic contaminants via biological oxidation. The process utilises nutrients in the waste water (i.e. nitrogen and phosphorus) in addition to organic contaminants for healthy cell synthesis to occur. In the biozone tank (20), the sewage undergoes strong aeration to encourage the growth aerobic bacteria and other microorganisms that oxidize the organic matter to carbon dioxide and water. Biomass grows on surface of the plurality of fixed media units (25) while the sewage passes over its surface. The surface area of the plurality of fixed media units (25) provides the nitrifying bacteria a habitat, ability to retain population and improves contact with wastewater. When the wastewater contains ammonia and the nitrifying bacteria are present, then oxygen is also used in the conversion of nitrogen forms leading to high BOD load. The high BOD load due to nitrifying bacteria is also taken into consideration while calculating quantity of air (oxygen) supplied to the bio-zone tank (20) through aeration.
In an embodiment, the fixed media units from the plurality of fixed media units (25) are structured units made up of FRP material normally having dimensions 1200 mm x 600 mm x 600 mm with longitudinal pitch ranging from 38mm to 40mm, spiral angle ranging from 28° to 30°, surface area per unit volume ranging from 250 m2/m3 to 260 m2/m3 and minimum fill thickness of 0.25mm. The fixed media units (25) are stacked to a certain height and width to give required surface area and volume of the media calculated based on the incoming BOD loads. The dimensions of the biozone tank (20) are considered in such a way that the media fits the biozone tank (20) perfectly providing the required surface area for the bacteria growth. In other words, the number of fixed media units (25) is calculated based on the incoming BOD loads.
In an embodiment, the fixed media units (25) are stacked vertically to reduce the footprint. The height of the stacked fixed media units (25) is decided based on blower heads available. The plurality of fixed media units (25) is fit in the biozone tank (20) in such a way that it does not move at all.
The biomass liquor in the biozone tank (20) then enters the settling tank (30). The suspended solids in the liquor overflown from bio zone tank (20) are separated in the settling tank (30). The settling tank (30) is a tube settler system provided with parallel plates to enhance the settling in lesser space. The sludge settles at hopper bottom. The tube settler (30) is the most effective and alternative to the conventional sedimentation process, unlike the sedimentation process that demands a great deal of today's valuable space. Tube settler (30) is inexpensive solution for drinking water and wastewater plants to increase treatment capacity, reduce new installation footprints, improve effluent water quality, and decrease operating costs.
Tube settlers are commonly used in rectangular clarifiers to increase the settling capacity by reducing the vertical distance a suspended particle must travel. High efficiency tube settlers use a stack of parallel tubes, rectangles or flat pieces separated by a few inches (several centimeters) and sloping upwards in the direction of flow. This structure creates a large number of narrow parallel flow pathways encouraging uniform laminar flow as modeled by Stokes' law. These structures provide a very large surface area onto which particles may fall and become stabilized and help to aggregate very fine particles that can settle as the flow exits the plates, as the flow is temporarily accelerated between the plates and then immediately slows down. Structure inclined between 450 and 600 allows gravity drainage of accumulated solids, but shallower angles of inclination typically requires periodic draining and cleaning. Tube settlers allow the use of a smaller clarifier and may enable finer particles to be separated with residence times less than 10 minutes. Typically such structures are used for difficult-to-treat waters, especially those containing colloidal materials. Tube settlers capture the fine particles allowing the larger particles to travel to the bottom of the clarifier in a more uniform form. The fine particles then build up into a larger mass which then slides down the tube channels. The reduction in solids present in the outflow allows a reduction in the clarifier footprint when designing. Tubes made of PVC plastic are a minor cost in clarifier design improvements and may lead to an increase of operating rate of 2 to 4 times. The purpose and function of the settling Tank (30) is:
• To allow settling of biomass solids in the Mixed Liquor (biomass slurry) coming out of the Bio zone tank, to the bottom of the clarifier,
• To thicken the settled biomass, in order to produce a thick underflow, and
• To produce clear supernatant water, in the overflow from the clarifier.
The settling tank (30) is only a passive device and the fluid movements occur under the influence of gravity. From the settling tank (30), a clear water is taken to the tertiary treatment zone (C) and sludge is taken into a sludge holding tank (40).
Treatment of sewage in the pre-treatment zone (A) and the biological treatment zone (B) do not remove all the biological degradable organic matter. The purpose of tertiary treatment zone (C) is to provide a final treatment stage to further improve the effluent quality before it is discharged to the receiving environment.
The tertiary treatment zone (C) includes a chlorine contact tank (50) and a sand filter (70). Clear supernatant water from the settling tank (30) is taken in the chlorine contact tank (50) receiving NaOCl dosing from a chlorine dosing unit (60). The NaOCl dosing is done in chlorine contact tank (50) to reduce/kill the bacteria and micro-organism. Chlorine solution is metered into the effluent by an electric dosing pump paced according to the sewage inflow. The effluent is retained in the baffle walled chlorine contact tank (50) for a minimum of 30 minutes for effective disinfection prior to discharge. The chlorine treated water is pumped to the sand filter (70) through a filter feed pump (65) for trapping the traces of solids that escape the settling tank (30).
The sand filter (70) is provided to remove suspended solids. The chlorine treated water is entered from the top thereof and exits through the grades of media. During the course of filtration, a bed is compacted raising the differential pressure across the sand filter (70). To clean the media, backwash of the filter is done at regular interval. Auto valve shall be used for operation.
In an embodiment, the sand filter (70) is a pressure sand filter. The pressure sand filter, also known as a dual media filter are used to remove the turbidity and suspended solids from the water. The filter media generally used is sand-anthracite, inside the filter there is a layered bed of filter media. It provides very efficient particle removal under high filtration rate. Sand is used to remove the suspended particles and anthracite is used to remove the odor and color etc. to make the water fit for different applications. A sand-anthracite filter or Dual Media filter is primarily used for the removal of turbidity and suspended solids as low as 10-20 microns. Dual media filters provide very efficient particle removal under the conditions of high filtration rate. Inside a sand-anthracite filter is a layered bed of filter media. The dual media filter can operate for much longer periods of time (five or more times as long at the same filtration rate), before backwashing is necessary because the bed can hold more turbidity. Turbidity is trapped and held throughout the entire bed depth, rather than the top one or two inches. Another important advantage is that the dual media filter can clarify water at a much higher flow rate than a single-media sand filter.
The filtered clear water from the sand filter (70) is finally collected in a product water tank (80).
Referring to figures 2A and 2B, the equalization tank (10), the biozone tank (20), the settling tank (30), the sludge holding tank (40), the chlorine contact tank (50) and the sand filter (70) are mounted on a single platform so that whole plant is lifted at one go. In an embodiment, the system (100) is built in MSEP (Mild Steel Epoxy Painting) for smaller capacities up to 20KLD which has least possible foot-print and power consumption. Sludge generation in the system (100 is at its lowest as yield is just 10% meaning only 10% of BOD load is converted into sludge volume with 1% consistency.
Dimensions of the system (100) and dimensions of components of system (100) can be changed depending upon availability of space i.e. system (100) can have different length and width for one capacity keeping the media volume and available sizes intact and at the same time, achieve the abovementioned design specialities mentioned e.g. a system for 100 KLD capacity can have a width of 1.2 meters or 1.8 meters or 2.4 m as well.
The system (100) is designed for domestic sewage comprising of following assumed inlet conditions:
BOD5: 350 ppm (max)
COD: 600 ppm (max)
Suspended Solids: 150 ppm (max)
Oil and grease: 10 ppm (max), wherein the product water received in the product water tank (80) shows BOD5 less than 20 ppm and contains suspended solids less than 5 ppm.
The treated water received from the system (100) can be reused for gardening, toilet flushing, floor washing, car washing, etc.
Advantages of the invention
• The system (100) is a modular / customizable system and can be varied in nature and capacities without disturbing the existing.
• The system (100) can be transferred from one place to another without any civil work requirement due to modular design.
• The system (100) has low maintenance cost, it is low on civil work and requires less space.
• The system (100) is operable by a semi-skilled labor.
• The system (100) has no moving parts except for pump and blower.
• The system (100) has least footprint as it uses fixed media.
• The treated water is not having foul odour and can be totally recycled and reused for gardening, car washing, floor washing and similar other applications.
• The system (100) solves local body problems of land acquisition, capital etc.
• Sludge generation in the system (100 is at its lowest as yield is just 10% meaning only 10% of BOD load is converted into sludge volume with 1% consistency.
The forgoing objects of the invention are accomplished and the problems and shortcoming associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed description of the preferred embodiment is provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as representative basis for teaching one skilled in the art of employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modification and alterations may be made without departing from scope of the invention.

,CLAIMS:We claim:
1. A decentralized wastewater management system (100) comprising:
an equalization tank (10) fitted with a screening unit (4) and a sewage transfer pump (6), wherein the wastewater is received into the equalization tank (10) through an inlet pipe fitted thereto and passed through the screening unit (4) for solids removal;
a biozone tank (20) receiving pre-treated wastewater from the equalization tank (10) and fitted with at least one air blower (15) for aeration of the pretreated water, the biozone tank (20) having a plurality of fixed media units (25) stacked tightly therein to a height and width to provide a surface area and volume sufficient for growth of biomass for complete nitrification of ammoniacal nitrogen;
a settling tank (30) receiving the biomass liquor from the biozone tank (20), wherein suspended solids separated from the biomass liquor are allowed to settle at the bottom under the influence of gravity to form a sludge;
a sludge holding tank (40) receiving sludge from the settling tank (30);
a tertiary treatment zone (C) including a chlorine contact tank (50) and a sand filter (70) receiving clear supernatant water from the settling tank (30) for chlorine treatment and sand filtration thereby forming a filtered clear water;
wherein the equalization tank (10), the biozone tank (20), the settling tank (30), the sludge holding tank (40), the chlorine contact tank (50) and the sand filter (70) are mounted on a single platform.
2. The decentralized wastewater management system (100) as claimed in claim 1, wherein the screening unit (4) has mesh screens of varying sizes optimized for solids removal.
3. The decentralized wastewater management system (100) as claimed in claim 1, wherein the fixed media units from the plurality of fixed media units (25) are structured units made up of FRP material
4. The decentralized wastewater management system (100) as claimed in claim 1, wherein volume of air supplied through the air blower (15) is calculated depending upon total organic matter in the waste water.
5. The decentralized wastewater management system (100) as claimed in claim 1, wherein the settling tank (30) is a tube settler system provided with parallel plates to enhance the settling in lesser space.
6. The decentralized wastewater management system (100) as claimed in claim 1, wherein the sand filter (70) is a pressure sand filter.
Dated this on 14th day of December, 2020

Ashwini Kelkar
(Agent for the applicant)
(IN/PA-2461)