A device and method for household grey water treatment and reuse

Abstract

The present invention discloses a modular treatment system and its operational method that enables recovering reuse-quality water from grey water discharged from individual houses and apartments. The present invention serves as a replacement for the existing soak pits where the grey water is disposed of without any treatment, leading to contamination of water environment. The invention integrates anaerobic and aerobic biofilms on natural fibre and various macrophytes to treat greywater effectively. It is particularly suitable for household and community-level applications, offering a sustainable solution to reduce freshwater consumption and mitigate water pollution.

Description

[0001] A DEVICE AND METHOD FOR HOUSEHOLD GREY WATER TREATMENT AND REUSE

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a device and a method for the treatment of grey water discharged from individual houses. In particular, the present invention provides a device and method designed to process greywater— originating from sources such as bathrooms, kitchens, and laundry areas— to recover water of a quality suitable for various non-potable applications, including toilet flushing, gardening, and cleaning. The instant invention will be an improved replacement over the conventional soak pits which typically dispose grey water without any treatment. The recovery of reuse quality water from this device will reduce freshwater consumption at household level. The invention finds immense application in wastewater treatment, especially household greywater treatment. It shall help attain the 6thsustainable development goal (SDG) of clean water and sanitation.

[0004] BACKGROUND OF THE INVENTION AND DESCRIPTION OF PRIOR ART

[0005] Domestic wastewater, (Sewage) comprises two primary component : the black water and the grey water. The entire wastewater from a house (except toilet flush) including from kitchen sink, washing machine, bathtub, washroom, etc. is collectively called the grey water (Sullage). The toilet flush water (with feces) is called the black water. Notably, grey water constitutes approximately 80% of the total wastewater discharged from households

[0006] The normal practice of managing the grey water (especially in rural areas and urban settlements without sewerage connection) is direct disposal without any treatment in soak pits. This grey water contains various contaminants, including Organics (COD ~300 mg / L, BOD ~150mg / L), Nutrients (TN~20 mg / L, TP~5 mg / L), Fat and oil, Detergents, Emerging micropollutants (such as different chemicals, synthetic nano materials, micro-plastics, etc.), Pathogens, etc. Therefore, the disposal without treatment of the grey water is one of the major reasons for the contamination of both ground water and surface water sources causing various environmental and public health challenges. However, compared with sewage, the pollution load (especially the pathogen) of grey water is less. Therefore, by adopting appropriate treatment technologies, the household grey water can be treated and reused for different purposes or disposed of (for ground water charging) safely without imparting any negative effect on environment and public health.

[0007] The recovery of reuse quality water from grey water will reduce the consumption of fresh water at household level that will have an additional positive impact on the environment and society. Moreover, to comply with environment regulations, there is a great demand for robust onsite wastewater treatment systems as reported by Van Lier, J.B., Lettinga, G. (1999). Appropriate onsite technologies need of the hour for effective management of community wastewater (domestic waste waters, Water Sci. Technol. 40, 171-183; Metcalf & Eddy, 2003, Wastewater Engineering: Treatment and Reuse, fourth ed. McGraw Hills, New York).

[0008] There are a few patent documents and non-patent reports on treatment systems for wastewater, including sewage and specifically for grey water. But, a small scale, modular treatment system with very low capital and operational expenditure, suitable for recovering reuse quality water from grey water at a household level is never reported. In this scenario, the present invention discloses an innovative treatment system for generating reuse quality water from household greywater in a sustainable way. Compared with the existing background reports, the treatment device developed in the present invention and method thereof addresses the gap left by prior art.

[0009] Constructed wetlands, membrane filtration systems, electrocoagulation, etc. are the most common treatment methods / systems reported for grey water treatment. In the case of constructed wetlands, the filter bed used plays a crucial role in the treatment. The microbial biofilm forming on top of the filter bed is mostly responsible for the pollutant removal. Various materials, both inorganic and organic filter bed have been reported. Gravels of different sizes, agro wastes, industrial wastes, synthetic media, etc. are most used filter bed in these kind of treatment systems. Among the previously reported onsite grey water treatment systems, a few have similarity with the general outlay of the present invention. However, the key features of the present invention make it different, and a better substitute than those reported in the prior art.

[0010] Several studies have reported the significance of "decentralized wastewater treatment systems" also known as "onsite wastewater treatment systems" or "off-the-grid wastewater treatment systems", as well as their potential to recover reuse quality water, bioenergy, and fertilizer. An overview of the potential resource recovery from wastewater was reported by Li et al., 2015; Reuse water pollutants. Nature, 528 (7580); 29-31.

[0011] Some of the most common types of onsite wastewater treatment technologies include the Moving Bed Bioreactor (MBBR) process, Membrane Bioreactor (MBR) process, Sequence Bioreactor (SBR) engineered ecosystems (Phytoremediation) systems, etc. However, these technologies have inherent limitations such as large space requirement (as in Phytoremediation) and energy requirement (as in SBR, MBBR), significant carbon footprint due to the greenhouse gas emissions (CH4, NO2 & CO2), challenges in secondary sludge disposal (SBR, MBBR), limited to secondary treatment alone, not designed for recovering bioenergy or fertilizer, etc.

[0012] Reference may be made to Manzoor and Zhou (2019) who reported a review on the wetland systems used for the treatment of wastewater globally (Manzoor and Zhou, 2019; Appl Ecol. Environ Res. 18(1) 107-127). Both organic and inorganic material was used as biofilter media in onsite wastewater treatment systems. In one of the studies, peat based biofilter medium was used (Talbot et al., 1996). The anaerobic module therein encloses a very unique bacteria carrier medium; a biopolymer (Structured filter bed, formed of high lignin containing natural fibre) based filter bed, which is environment friendly and biodegradable (Water Science and Technology, 1996, 34, 435-441). However, the drawbacks associated with this document are that it uses peat as the filter-bed for the fixed film type treatment unit. On the other hand, the present invention uses a plant microbial system for the wastewater treatment. Moreover, the filter bed used in the present invention (needle-felt coir fibre) is more durable (high lignin content) with high porosity and surface area (without clogging), which is more advantageous compared to peat.

[0013] A system and method for processing and reusing gray water is disclosed in the patent application WO 2010 / 041246 Al, wherein the treatment unit consists of at least two vertical flow wetland units, each of which comprising a container filled with at least one granular substrate and at least one species of a hygrophilous plant, and an outlet. At least one of the wetland units is set to an inactive state during a predetermined period such that influx of graywater to each of the inactive units is prevented, whereby to regenerate each inactive wetland units. At least one of the wetland units is set to an active state to allow introduced graywater to be purified. Purified graywater is discharged from the outlet of each active unit to a sink. At least a portion of the purified graywater is recirculated to each active wetland units so that a portion of the purified graywater, when desired, is discharged to a domestic site for reuse. However, the drawbacks associated with this document are that minimum two treatment units are required and hence high installation cost. On the other hand the present invention uses a compact, modular, single treatment unit with lower installation cost.

[0014] Reference may be made to US 2023 / 0132622 Al that discloses a greywater treatment system including a first modular greywater processing apparatus having a raw greywater inlet, a mechanical (MTF) filter connected to the raw greywater inlet, an ultrafine (UF) filter connected in series downstream of the mechanical filter. The filtrate outlet is connected to a processed water outlet. However, the drawbacks associated with this document are that the treatment system therein is physical filtration involving more energy input. On the other hand the present invention is a biological treatment system with very low energy input (which is optional).

[0015] Reference may be made to the report on treatment of wastewater including grey water as disclosed in WO 2010 / 108226 Al. It is a simulated wetland system, where the filtration medium used was gravel, sand or synthetic filter medium to achieve the desired quality of the treated water. However, the drawbacks associated with this document are that filter bed used is the conventional gravel, sand or synthetic media, the efficiency of such media are lower compared to the unique nature based filter bed (high lignin containing fibre) used in the present invention.

[0016] Reference may be made to US 674378B2 which discloses a wetland treatment system for removing contaminants in wastewater including storm water runoff, grey water etc. The system can remove different contaminants in the wastewater. The treatment is achieved through vegetative filtration media consists of porous materials and filters including absorbent polymer, Perlite and / or Zeolite. However, the drawbacks associated with this document are that high cost, durability and un sustainable. On the other hand, the unique medium used in the present invention is high lignin containing natural fibre based, that provide any advantageous and better performance of the treatment unit. Reference may be made to KR 20080114259 that discloses a treatment method for greywater using constructed wetland and related apparatus. Chips and thick zeolite are mainly used in the wetland system. However, the drawbacks associated with this document are that lower surface area for microbial growth, heavier weight, lack of biodegradability, higher cost, and reduced sustainability. In contrast, lignin-rich natural fibres as in the present invention are lightweight, porous, renewable, and support better microbial colonization, that enhances the performance of the treatment system.

[0017] Reference may be made to multistage greywater treatment system including at least one separation stage, one solid removal stage, and a disinfection stage is disclosed in EP 4095105 Al. However, the drawbacks associated with this document are that the high cost involved due to a multistage system. On the other hand the present invention is a compact single treatment unit in which the associated plant-microbial system purify the greywater.

[0018] Reference may be made to WO 2022 / 165594 Al which discloses a multi-stage system for treating greywater comprising an electrochemical treatment module configured to carry out electrooxidation and electrocoagulation processes and a filtration module comprising a multistage filtration system for the treatment and removal of chemical and biological contaminants in greywater. Reference may also be made to US 11655171 B2 that recites electrocoagulation as another method for wastewater treatment including black water and grey water. However, the drawbacks associated with this document are that high energy consumption, electrode wear and sludge production, chemical dependency (for pH adjustment), and technical complexity. On the other hand the present invention is a low- maintenance, environmentally benign wetland unit that offer many advantageous.

[0019] Reference may be made to CN 116715343 A which reports an iron-carbon reinforced microbial fuel cell type wetland for treating domestic grey water with organic matter as main pollutant. Gravel is the filler used in the wetland unit in this treatment system. However, the drawbacks associated with this document are the higher cost and technical complexity with MFC system. On the other hand the present invention uses natural fibre based wetland is better in terms of lower maintenance and environment impact. Reference may be made to US 8377291 B2 which reports a water recycling system that can be used for reclaiming and recycling water, wastewater, or grey water, for providing landscape irrigation, or for recycling uses such as for sanitary facilities. In this citation, a filter screen selected from wire mesh screen, wire mesh blanket, wire mesh tube, and a perforated screen were reported. However, the drawbacks associated with this document are that the filter bed mentioned as mostly synthetic with higher cost, and hence not environment friendly. On the other hand, natural fibre-based wetlands as in the present invention offer a low-cost and sustainable with superior microbial support and ecological integration, making them more suitable for decentralized greywater treatment.

[0020] Weragoda et al., 2010. Efficiency of coconut coir-pith as an alternative substrate in the treatment of submerged macrophyte wetland systems in tropical conditions. Chemistry and Ecology, 26(6), 427-440. https: / / doi.org / 10.1080 / 02757540.2010.5048Q6 reported the efficiency of coconut coir-pith as an alternate substrate for the treatment of domestic wastewater in a submerged macrophyte wetland. Both plants (Hydrilla verticillata) and microbes (aerobic and anaerobic) were used for the treatment. The treatment of greywater using an anaerobic baffle reactor followed by a column type filter bed with multi layers of gravel, activated carbon, coir fibre and sand [Sahara, Z., et al. 2022. Activated carbon and coconut coir with the incorporation of ABR system as greywater filter: Implications for wastewater treatment. Sustainability, 14(2), 1026. hit p s : / / d o . o rg / 10 , 3390 / s u 140210261. The treated water was found meeting WHO standards. However, the drawbacks associated with this document are that it is a multistage system with an initial ABR followed by a multilayer filtertation unit that included coir fibre as one of the layers. On the other hand the present invention is a compact and modular wetland system that uses needle felt coir fibre as the filter bed for more effective purification of the grey water.

[0021] Sanithagopal et al., 2024; Journal of Environmental and Chemical Engineering, 12, 112382 reported the application of needle-felt coir fiber as a natural substitute for synthetic medium for anaerobic fixed film reactors for wastewater treatment unit. However, the drawbacks associated with this document are that it was not a wetland technology, and also a post aerobic treatment was required for achieving the discharge standards. However, the present invention is a modular wetland (without any post treatment) for treating greywater from houses. Imura et al. .1995. Water Science and Technology, 1995, 31, 9, 163-171 reported a high- efficiency household greywater treatment system employing a flow equalization, anoxic-oxic recirculation biofilm process for removing organic matter and nitrogen. In details, the system includes a pretreatment process (sedimentation separation tank, anaerobic filter or equalization tank with screens) followed by an aerobic process (contact aeration, activated sludge, etc.). An onsite wastewater treatment systems with a series of anaerobic-aerobic units was reported previously by Ghunmi et al. 2010. Bioresource Technology, 2010, 101, 1, 41-50. The anaerobic unit is up-flow type with a one-day operational cycle, and the aerobic unit with mechanical aeration device. The COD removal efficiency reported was up to 64%, and the treated water was meant for irrigation. The treated grey water treatment was used for irrigation. However, the drawbacks associated with this document are that it is a multi stage treatment system with aeration that enhances the capital and operational cost. However, the present invention is a modular wetland with lower capital and operational cost.

[0022] It may be observed that none of the prior art documents either by itself or in combination entail all aspects of the current invention, i.e. they do not disclose any device or system for treating and reusing the greywater at household level in an environment friendly and economic way; wherein the sequence of events for treatment including exposing the greywater under alternate anaerobic and aerobic conditions created through the flow of greywater between the internal compartments for the purification of water; involving plantmicrobe interaction to complement greywater treatment; aerating the treated water and subsequently passing through an activated carbon filter further improve water quality, ensuring safe and sustainable reuse.

[0023] Therefore, keeping in view the limitations of the hitherto reported prior art, the inventors of the present invention realized that there exists a dire need to provide a modular type, compact treatment system to generate reuse quality water from household greywater, which is compact (with less carbon foot print) is portable (the most unique feature) making it different from similar systems; encompassing a sequence of events for treatment including exposing the greywater under alternate anaerobic and aerobic conditions created by the flow of greywater between the internal compartments for the purification of water; involving plant-microbe interaction; wherein needle-felt coir fibre is used for the biofilm development within the internal compartments of the treatment system (device), and the liquid flow (grey water) dynamics creates alternate oxic-anoxic conditions within a compartment, with the additional purifications steps such as aerating the treated water and subsequently passing through an activated carbon filter further improve water quality, ensuring safe and sustainable reuse.

[0024] OBJECTIVES OF THE INVENTION

[0025] The main objective of the present invention is therefore to provide a device and method for treating grey water discharged from households which obviates the drawbacks of the hitherto reported prior art.

[0026] Another objective of the present invention is to provide a device which will be a replacement for the conventional soak pits, enabling the treatment of greywater before disposal.

[0027] Still another objective of the present invention is to provide a device which is capable of recovering water of reuse=able quality water from the grey water at household level, thereby promoting water conservation.

[0028] Yet another objective of the present invention is to provide a device which is modular, scalable, and with low footprint and energy requirement for operation.

[0029] Still another objective of the present invention is to provide a device which uses both anaerobic and aerobic microbial system, and along with macrophytes for the purification of the grey water.

[0030] Yet another objective of the present invention is to provide a device which uses natural fibre as biofilm support medium, and for the macrophytes growth.

[0031] SUMMARY OF THE INVENTION

[0032] The invention focuses on the development of modular device for treatment of greywater (sullage) or household wastewater and for recovering reuse quality water.

[0033] It provides a device and method for treating grey water discharged from households, and recovering reuse-quality water. Grey water treatment is achieved thorough an integrated anaerobic and aerobic attached biofilm system supported by natural fibre and various macrophytes. This device offers a better replacement for the conventional soak pits which dispose of grey water without any treatment. This invention is particularly suitable for household and its ability to recover reuse quality-water will significantly reduce freshwater consumption at individual houses.

[0034] The treatment process involves subjecting the greywater to a series of alternating anaerobic and aerobic conditions within the internal compartments. This sequential exposure, facilitated by the flow of greywater, is the key driver of water purification. Additionally, aeration and the subsequent passage of the treated water through an activated carbon filter are employed to further enhance its quality. The interaction between plants and microbes, particularly the microbial flora associated with the unique filter-bed, also plays a significant role in the treatment of greywater.

[0035] The treatment system comprises a six internally compartmentalised structure made of various materials such as PVC, FRP, metal, or Ferro cement. The treatment unit has dimensions of 1.10 x 0.70 x 1.0 (all values in meters) and working volume of 600 liters. A vertical upward water flow is created in all compartments except the 6thchamber through internal PVC piping. Additionally, the wastewater flow through different compartments is exposed to alternate anaerobic-aerobic conditions from bottom to top, which help the anaerobic and aerobic microflora attached to the filter-bed medium to remove various contaminants. The compartments 1, 2, 3, and 4 are filled with needle felt coir fibers as the sole filter bed media. Furthermore, the tanks 1, 2, 3, and 4 have a steel frame (1 meter in height from the top edge of the tank) to support the growth of climbing plants. A mix of different monocotyledon plant varieties (Poly culturing) are planted in compartments 1, 2, 3, and 4. The treated water collected in Chamber 5 is aerated further (atmospheric air is bubbled using a fine diffuser) through an external device (aquarium type aerator). The treated and aerated water from Chamber 5 passes through Activated Carbon Granules filled in Chamber 6, before it is collected for reuse. The portable and compactness of modular device makes it unique from other similar systems.

[0036] BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0037] In the drawings accompanying the specification; Figure 1: The overall layout of the treatment system showing the preliminary treatment (collection tank), followed by the modular treatment system (device) for the grey water treatment and for recovering reuse quality water.

[0038] Figure 2: Schematic view of the modular treatment system with internal compartments (1,2 3, 4, 5 and 6), and the flow pattern (Arrows) of the grey water through the compartments to ensure removal of contaminants in the grey water.

[0039] Figure 3: Schematic view (Side view) of the modular treatment system showing internal compartments (1,2 and 5), and the flow pattern (Brocken line Arrows) of the grey water through the compartments to ensure anaerobic (bottom) and aerobic (top) conditions in chamber 1 and 4. Chamber 1 and 2 packed with the needle felt coir fibre as biofilm support matrix. Air at a flow rate of will be bubbled from the bottom of Chamber 5. The different macrophytes grow on top layer of the filter bed.

[0040] Figure 4: Schematic view (Side view) of the modular treatment system showing internal compartments (2, 3 and 6), and the flow pattern (Brocken line Arrows) of the grey water through the compartments to ensure anaerobic (bottom) and aerobic (top) conditions in chamber 2 and 3. Chamber 2 and 3 packed with the needle felt coir fibre as biofilm support matrix. Chamber 6 will have filled with activated carbon particles. The different macrophytes grow on top layer of the filter bed.

[0041] Figure 5: Schematic view (Front view) of the modular treatment system for grey water treatment. Internal compartments (1, 2, 3, and 4) are packed with needle-felt coir fibre for supporting the biofilm. The top layer of the fibre bed supported the macro-phytes, which mainly included monocot plants, ornamental plants and vegetable plants. The climbing plants will be supported on metal frame (as shown in the figure).

[0042] DETAILS OF BIOLOGICAL RESOURCES USED IN THE INVENTION

[0043] The details of plants used for the purposes of the present invention is provided herein below:

[0044] DETAILED DESCRIPTION OF THE INVENTION

[0045] The present invention discloses a modular onsite treatment system for recovering reuse quality water from grey water discharged from individual houses. The treatment of greywater is carried out through a sequence of events, all of which happen in a modular device, which is compact (less foot print) and also portable, which is the most unique feature of the present invention. The treated water from the developed device can be used for various applications at household levels, thereby reducing the freshwater consumption. The basic design of the present treatment system includes a fabricated (in PVC, FRP, Metal or Ferro cement) compact tank which is internally compartmentalized as shown in figure 1. The present treatment system can be placed above a levelled ground or it can be placed as subsoil up to 80% of its total height to prevent run off water entering into the unit. In Indian scenario, with per capita water consumption of 135 lit, a typical 5-member family generates ~400 Lit Greywater daily (CPHEEO, 2024). The total volume of the modular treatment unit will be 550 Lit, and the working volume will be 500 Lit, and its dimensions (L X B X H) will be 89 X 69 X 82 (all values in cm).

[0046] The entire treatment system consists of the following segments:

[0047] (1) A preliminary treatment unit

[0048] (2) The modular treatment unit

[0049] (3) Post treatment unit

[0050] The present invention is capable of treating greywater at household level with the following characteristics:

[0051] • COD in the range 50 to 500 mg / L,

[0052] • BOD in the range of 20 to 250 mg / L,

[0053] • pH in the range of 6 to 8.5,

[0054] • Total solids in the range of 50 to 600 mg / L,

[0055] • Total dissolved solids in the range of 100 to 300 mg / L,

[0056] • TKN in the range of 10 to 25 mg / L, and

[0057] • Total phosphorus in the range of 2 to 10 mg / L.

[0058] PRELIMINARY TREATMENT UNIT:

[0059] The preliminary treatment unit is a collection tank which is designed to normalize the flow rate of greywater from houses. Another function of the preliminary treatment unit is to settle large solid particles (if any) in the grey water. It also removes excess fat / oil and grease (if any) in the greywater. For a five-member family, the preliminary treatment unit typically consists of a 100-liter tank made of PVC. It can be separate, connected in series or integrated with the modular treatment device. MODULAR TREATMENT UNIT:

[0060] The grey water from the preliminary treatment unit is directly passed to the Modular treatment unit. This unit can be fabricated from FRP reinforced with a metal frame, SS (304), MS with inside epoxy coating, Ferro cement orwith any suitable similar material that tolerates mechanical stress, and corrosion. All internal piping is made of PVC. The unit can be placed above the soil level or with 80% of its height below the soil level.

[0061] The internal compartments of the modular treatment system (except the aeration and activated carbon packed) are filled with multiple layers of needle-felt coir fibre as packing medium (substrate) for the biofilm development. The application of needle-felt coir fibre as packing medium (replacing the conventional gravel or industrial wastes) in the modular treatment device for greywater treatment is the uniqueness of this invention. Needle-felt coir fibre is high lignin (40-48% by weight) containing coir fibre, mechanically bonded into 5 mm to 5 cm thick layer. Multiple layers are packed in a single chamber in the modular treatment unit. The greywater in each chamber flows from bottom to top in all the chambers using the piping within the compartments with the bottom portion of the needle felt coir fibre packed chamber being anaerobic, while its top portion being aerobic.

[0062] At the beginning, the modular treatment system is inoculated with activated sludge which is a mixed microbial system comprising predominantly anaerobic and aerobic bacteria, archaea, protozoa, Rotifers, Micro-metazoa, etc. When the greywater starts passing through the filterbed, a self-adapted microbial system evolves that predominates the treatment module which is responsible for the greywater treatment.

[0063] In addition to the filter-bed associated biofilm, a group of macrophytes are grown on the top layer of the fibre-based filter bed in compartments which also play a role in the grey water treatment. A poly culture (different plant varieties) approach is followed in the modular treatment system. The major macrophytes includes monocot plants like Acorus calamus (Sweet flag), Cymbopogon flexuosus (Lemon grass), Chrysopogon zizanioides (Vetiver). Other ornamental plans including Cana indica, Heliconia, Leman minor, etc. can also be included. Apart from ornamental plants, different vegetable plants can also be grown in the modular treatment device. For anchoring the macro-phytes, a layer of fine gravel (5 mm) will be placed on top of the top layer of the filter bed. The climbers can be supported with additional frame attached with the modular unit.

[0064] As a general process scheme, the greywater after preliminary treatment (as detailed above), is introduced into different internal compartments of the developed device which are connected in series (figure 2). While the greywater passes through different compartments, it is exposed to alternate anaerobic (bottom) and aerobic (top) conditions of the filter bed medium. The anaerobic and aerobic microbial communities attached with the fibre-based filter bed remove the contaminants (organics and nutrients) in the greywater. The macrophytes as well as the roots associated microflora also play a major role in the purification of grey water. The hydraulic retention (HRT) required for the present treatment system for purifying grey water is around 24 hrs. The high surface area and high porosity of the filter bed used in this study is one of the significant factors for the performance of the present treatment system. While the greywater passes through the different compartments, around 80 to 90% of the inlet COD is removed by the collective action of the filter bed associated biofilm and the macrophytes. The residual COD and Odour (if any) in the treated water is removed while it passes through the aeration chamber (5) and subsequent activated carbon filled chambers (6). The final treated water can be directly used for different application such as irrigation, gardening or for recharging ground water. The final treated water from the invented system meets all discharge standards in terms of COD, BOD, NH4-N, PO4-P, etc.

[0065] POST TREATMENT UNIT:

[0066] The treated water is collected, and its quality further enhanced by integrating with micro / ultra-filtration and disinfection modules for different applications including floor / vehicle washing, toilet flushing etc.

[0067] In an aspect, the present invention provides a modular grey water treatment system and method, designed to recover reuse-quality water for various applications, wherein the system comprises: a) A compact and modulardevice with internal compartments packed with a filter medium (filter bed), augmented with an anaerobic microbial consortium dominated by hydrolytic bacteria, mesophilic archaea, ciliated and flagellar protozoa, rotifers, and nematode worms. The flow of greywater through these internal compartments exposes the greywater to alternating anoxic and oxic conditions within the filter bed, allowing the attached biofilm to effectively remove contaminants; b) A top layer of needle-felt coir fiber in the filter bed, supporting the growth of various macro-phytes that enhance aerobic microbial activity and contaminant removal; c) Means for exposure to granular activated carbon and aeration towards the end of the process to enhance the quality of treated water.

[0068] In another aspect, the present invention provides a modular grey water treatment system wherein greywater treatment efficiency is collectively achieved by several factors, including: a) The physical structure of the device with internal compartments. b) The needle-felt coir fiber used as the filter bed. c) The biofilm attached to the filter bed. d) The liquid flow dynamics within the system. e) The macrophytes growing on the top layer of the filter bed. f) The external aeration and the activated carbon filter bed in the treatment flow path.

[0069] In still another aspect, the present invention provides a modular grey water treatment system wherein the filter bed comprises mechanically bonded needle-felt coir fiber arranged in multiple layers. The use of needle-felt coir fiber as a biofilm development medium is an inventive step. This medium provides a high surface area for microbial colonization and is mechanically bonded to ensure durability and efficiency in contaminant removal.

[0070] In yet another aspect, the present invention provides a modular grey water treatment system wherein the needle-felt coir fiber-based filter bed functions as the sole biofilm support matrix for both anaerobic and aerobic microflora in different compartments. It also acts as a physical barrier for suspended organics in the greywater, providing their digestion and complete removal.

[0071] In still another aspect, the present invention provides a modular grey water treatment system wherein the integration of macrophytes such as Acorus calamus, Cymbopogon flexuosus, Lemna minor and Chrysopogon zizanioides in the filter bed enhances the treatment process. The combination of biofilm and plant roots provides a dual-action purification system, which is a unique feature of this invention.

[0072] In yet another aspect, the present invention provides a modular grey water treatment system designed to be modular and scalable, making it adaptable for different household sizes and water treatment needs addressing the common limitations of space, cost, and complexity. The system is suitable for decentralized (onsite / off-grid) treatment of greywater from houses with wide COD ranges (50 to 500 mg / L) and capable of removing more than 90% of the inlet COD. It is compact in design and requires minimal energy requirements.

[0073] The efficiency of the present invention to treat organic rich wastewater, and recover reusequality water and bioenergy has been tested in a case study at pilot scale, and the details are as follows:

[0074] ♦♦♦ A six chambered structure of greywater or sullage treatment unit was constructed with 550 Lit of working capacity where all the chambers were attached with PVC, FRP, Metal or ferro cement. Chambers 1 to 4 provide plantation in fine sand on top of the tank and aerobic microflora on the upper side and anaerobic microflora at bottom of the tank with coconut coir as supporting material. The coir acts as a sole filter bed media when water flows vertically and uniformly at flow rate of 23 ± 0.2 L / hour in the chambers. Metal frame of IM height is attached from top edge of the tank to support the growth of climbing plants. The 5thchamber provides aeration; and the activated carbon filtration in the 6thunit finally produces reusable water.

[0075] Therefore, the above illustrated combination of six chambers and their unique properties makes the system of the present invention novel and inventive with both technical and functional advantages and contributes to the overall inventiveness of the process.

[0076] EXAMPLES

[0077] The following examples are given by way of illustration only and therefore should not be construed to limit the scope of the present invention in any manner.

[0078] Example 1: Treatment of high strength organic wastewater from a canteen A modular, grey water treatment unit based on the present invention was fabricated, and it was tested for treating ~ 500 Litre greywater from a departmental canteen. The treatment system (500 Lit capacity) in this case was fabricated in Fibre Reinforced Plastic (FRP). It consists of six internal compartments (named 1 to 6). The preliminary treatment unit was a 500 lit capacity PVC tank. Grey water after preliminary treatment was directly passed (gravity flow) into the first chamber of the modulartreatment unit, and from there to the subsequent chambers connected in series (Figure 2). The filter-bed was initially inoculated with a mixed microbial culture including both anaerobic and bacteria, archaea, protozoa and micrometazoa. The macrophytes grown on the top layer of the fibre-based filter bed in compartments 1, 2, 3 and 4 included mainly 4 varieties such as Acorus calamus (Sweet flag), Cymbopogon flexuosus (Lemon grass), Chrysopogon zizanioides (Vetiver), and Cana indica. Other ornamental (including flowering) plants were also grown for enhancing the aesthetic look of the treatment system. The treatment system was operated for about six months period. The performance data of the treatment system including inlet grey water characteristics and outlet treated water characteristics are summarized in Table 1. The treated water meeting discharge standards for inland application was used for gardening purpose.

[0079] Table 1: Performance details of a modular greywater treatment and reuse system

[0080] Example 2: Design calculations of the modular wetland system for greywater treatment.

[0081] The following design details are assumed for a typical 5 member's family discharging maximum 400 Lit (0.4 M3) greywaters per day.

[0082] Volume of the modular treatment system = 500 lit Greywater flow rate = 400 lit / day

[0083] Surface area of the treatment unit = 0.614 M2

[0084] The Hydraulic Loading Rate = 0.615 meter / day

[0085] Hydraulic Retention Time (HRT) = 1.26 days (typical range, 2-5 days)

[0086] Volumetric Hydraulic Loading Rate = 0.79 / Day Surface Loading Rate or COD Loading Rate (CODL) = 195 g / M2 / day (typical range, 100-200 g / M2 / day).

[0087] Organic Loading Rate (OLR) = 238.5 g / M3 / day (typical range, 50-300 g / M3 / day) Comparing the observed values with the typical range of values reported for engineered wetlands, the present invention was fond to be a better performer.

[0088] Example 3: Comparing the performances of two modular wetland units, one with Garden plants and other with Vegetable plants. Two modular wetland units were prepared based on the present invention. One of the units was planted with garden plants (including the plants listed). A second unit was planted with vegetables plants like tomato, spinach, mint and egg-plant. Wastewater from a departmental canteen after dilution (bringing down the strength to greywater level) was fed to both the units. After two months of continuous operation, its performance was assessed based on important water quality parameters. The results are consolidated and presented in the following table.

[0089] Example 4: Assessing the performance of the modular wetland unit in Pathogen removal.

[0090] Based on the design of present invention, two modular wetland units were prepared One of the units was planted with garden plants (including the plants listed in the patent). A second unit was planted with vegetables plants like tomato, spinach, mint and egg-plant. Wastewater from a departmental canteen after dilution (bringing down the strength to greywater level) was fed to both the units. After two months of continuous operation, its performance was assessed based on pathogen removal. The results are consolidated and presented in the following table.

[0091] The results indicated the high efficiency of the present modular wetland unit to control pathogen load in the greywater.

[0092] ADVANTAGES OF THE INVENTION COMPACT AND SPACE-EFFICIENT DESIGN Compact size (less footprint), which is highly advantageous for urban areas with limited space availability. PORTABILITY AND FLEXIBILITY

[0093] Since the unit is compact and portable it can be moved from one location to another even after started working. This flexibility is advantageous for house owners providing them convenient. PREFABRICATED MODULAR CONSTRUCTION

[0094] The present Modular treatment system is prefabricated ,that will eliminated the nedd for civil construction (hence cost also) at the installation site, which is common in usual wetland systems, thereby reducing installation time and overall costs. HOUSEHOLD-LEVEL WATER REUSE

[0095] The present system can recover reuse quality water from greywater at household level. This will reduce freshwater consumption at household level. ENHANCED AESTHETIC APPEAL THROUGH POLY-CULTURING The poly-culturing approach (using different plant varieties) with high aesthetic look, which is ideal for a household level. SUPPORT FOR VEGETABLE PLANT GROWTH

[0096] The present system can support the growth of vegetable plants at household level without water or nutrient supply. CUSTOMIZABLE AND RETROFITTABLE

[0097] The unit can be customized and retrofitted with existing site conditions. The present system can handle change in greywater quality (varying organic strength). WIDE RANGE ORGANIC LOAD HANDLING The present system can handle greywater with a wide organic strength (COD 50 to

[0098] 500 mg / L).

Claims

WE CLAIM:

1. A device for household grey water treatment and reuse configured for recovering reusequality water from greywater discharged from individual households, comprising:• a preliminary treatment unit configured for receiving greywater from individual houses, settling suspended solids, and removing oils and grease;• a modular treatment unit connected to the preliminary treatment unit and comprising multiple internal compartments configured for supporting anaerobic and aerobic treatment environments, wherein: o each internal compartment is being packed with multiple layers of needle felt coir fibre configured for facilitating biofilm formation and wastewater filtration; o a mixed microbial inoculum being seeded onto the filter bed for initiating anaerobic and aerobic degradation of contaminants; o one or more macrophytes being planted on a fine gravel layer placed over the top of the coir fibre layer being configured for nutrient uptake and additional biological treatment;• internal piping (made of PVC) being provided within the compartments and being configured for allowing bottom-to-top greywater flow through each compartment;• an aeration chamber and an activated carbon packed chamber being configured for final polishing of treated water and odour removal; a post-treatment unit being connected downstream of the modular treatment unit and being configured for integrating micro / ultra-filtration and disinfection modules for improving water quality for non-potable reuse applications.

2. The device as claimed in claim 1, wherein the preliminary treatment unit is constructed using a polyvinyl chloride (PVC) tank, the tank being configured to operate either as a separate unit, in series connection, or as an integrated component with the modular treatment unit.

3. The device as claimed in claim 1, wherein the filter bed is comprising mechanically bonded needle-felt coir fibre arranged in multiple layers, the needle-felt coir fibre being configured for providing a high surface area for microbial colonization and being mechanically bonded for ensuring durability and sustained efficiency in contaminant removal.

4. The device as claimed in claim 1, wherein the needle-felt coir fibre-based filter bed being configured to function as the sole biofilm support matrix for both anaerobic and aerobic microflora across different compartments, the filter bed being further configured to act as a physical barrier for suspended organics in the greywater, thereby facilitating their digestion and complete removal during continuous flow through the system.

5. The device as claimed in claim 1, wherein the macrophytes are selected from Acorus calamus, Cymbopogon flexuosus, Lemna minor and Chrysopogon zizanioides being integrated into the top layer of the filter bed, the macrophyte root systems being configured to act synergistically with the biofilm for providing a dual-action purification mechanism, thereby enhancing the efficiency of greywater treatment.

6. The device as claimed in claim 1, wherein the internal compartments of the modular treatment unit being fabricated from materials selected from fibre-reinforced plastic (FRP), stainless steel (SS 304), epoxy-coated mild steel (MS), or ferrocement, the materials being selected for providing structural strength, corrosion resistance, and durability under continuous operational conditions.

7. The device as claimed in claim 1, wherein the modular treatment unit is installed with 80% of its height remaining below ground level, the unit being alternatively configured for above-ground placement based on site conditions.

8. The device as claimed in claim 1, capable of treating household greywater with:• COD in the range of 50 to 500 mg / L,• BOD in the range of 20 to 250 mg / L,• pH in the range of 6.0 to 8.5,• total solids in the range of 50 to 600 mg / L,• total dissolved solids in the range of 100 to 300 mg / L,• total Kjeldahl nitrogen (TKN) in the range of 10 to 25 mg / L, and• total phosphate in the range of 2 to 10 mg / L.

9. The device as claimed in claim 1, wherein the household greywater treated thereby exhibit:• COD less than 50 mg / L,• BOD less than 10 mg / L,• total solids below 100 mg / L,• TKN less than 5 mg / L,• total phosphate less than 2 mg / L, and• total coliform count being nil.

10. A process for treating greywater using the device as claimed in claim 1, wherein the steps comprising:collecting greywater from difference sources (kitchen, bathroom, laundry, etc., except toilet flush out) to the preliminary treatment unit, settling and removing the settleable solids;(ii) introducing (pumping or by gravity flow) the greywater after preliminary treatment in step (i) to the modular treatment unit at a uniform flow rate of23±0.2 l / hour and HRT of around 24 to 28 hours;(iii) allowing the wastewater to pass through the different compartments of the modular treatment unit;(iv) removing the residual COD and odour in the treated water of step (iii) by passing through the aeration chamber (5) and activated carbon filled chambers (6);(v) the final treated water obtained in step (iv) being directly used for different applications as irrigation, gardening or for recharging ground water.

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