WO2017029682A1

WO2017029682A1 - System of treatment of sewage waste for on-site sanitation

Info

Publication number: WO2017029682A1
Application number: PCT/IN2016/000210
Authority: WO
Inventors: Ajeet OAK; Rohit PATANKAR; Vishal UJAGARE; Walter Thomas Gibson
Original assignee: Primove Infrastucture Development Consultants Pvt. Ltd.; Bear Valley Ventures Ltd.
Priority date: 2015-08-18
Filing date: 2016-08-18
Publication date: 2017-02-23

Abstract

Disclosed is a system for treatment of sewage waste for on-site sanitation. The system comprises a tank configured below ground level with outer surface of the tank filled with soil. The tank includes a plurality of holes configured on sides thereof to allow liquid flow out into the surrounding soil. Further, the system comprises at least one lid covering the tank. The lid is secured to the tank with an air gap around a perimeter of the lid. Furthermore, the system comprises an inlet pipe connected to the tank and a worm bed configured within the tank. The system also comprises a filter bed arranged in the tank beneath the worm bed, the filter bed comprising at least three layers of drainage media acting as secondary filters.

Description

SYSTEM OF TREATMENT OF SEWAGE WASTE FOR ON-SITE SANITATION

Field of the invention: The present invention generally relates to a system used for treatment of sewage waste for on-site sanitation, and more particularly, to the system used for active digestion and treatment of faecal waste by vermifilters.

Background of the invention:

Conventional sanitation solutions such as pit latrines and septic tanks contain faecal waste and help to prevent the spread of contamination. However, the breakdown of the waste inside these systems is slow, resulting in the accumulation of faecal sludge, which is expensive, difficult, and hazardous to remove. Furthermore, safe means of disposal may not be available. Therefore, a method for active digestion and treatment of faecal waste within a sanitation system is needed, more particularly for areas that have no prospect of being connected to a sewer system. One potential method is vermifiltration. Earthworms are well known^{^}to promote digestion of organic waste that results in the production of vermicompost. In vermifilters, this process is combined with filtration to digest faecal matter and treat the resulting liquid effluent on-site, i.e. at the site of production, for example adjacent to the home. On-site systems therefore do not require connection to a sewer network. The earthworms need only air, water and food to form a sustainable population in the vermifilter. The basic concept of a wet vermifilter for on-site sanitation has recently been described and proven (Furlong et al 2014a). It comprises a tank containing a vermifilter made up of two main components: a bedding layer at the top which provides a suitable environment for the worms and acts as a primary filter, and a drainage layer underneath which further treats the effluent. Simple designs were later developed which have been constructed from locally available materials such as bricks and mortar for field testing. The results of the field testing show promise [Furlong et al 2014 b) both in terms of performance ( faecal waste removal, effluent quality) and user satisfaction.

Prior to the work described by Furlong et al, a few patents and patent applications WO2001090007A1, WO1995007872A1, US5919366A, WO 1994006734A1, US20050006304A1 disclosed the use of filtration in combination with worms and other organisms for the treatment of faecal waste. The method, in the prior art patents, is referred to as biolytic filtration. In this method, the filtration matrix employed is usually compost ("humus") that may be supported by structural elements and arranged in a number of configurations. The US patent application US20050006304A1 disclosed that urine and faeces are separately treated and the liquid effluent is treated by passing through combinations of coarse and fine trickle bed media. The prior art patents also describe the use of pumps to recirculate effluent. Deficiencies or drawbacks in the Prior Art:

The prior art has a number of drawbacks. One problem is that many of the systems described in the patents cited above are too complex and expensive to be appropriate for applications in developing countries, where income levels are much lower. Although simpler, more affordable versions of the technology have been developed, these are not suitable for mass production and distribution because the components are made from heavy materials such as brick, concrete, sand, gravel and stones that are difficult to transport and time consuming to construct. Therefore, the existing technology cannot readily solve the challenge of providing the large scale sanitation that is needed in India and many other countries. Accordingly, there exists a need to provide a system of treatment of sewage waste for on-site sanitation that overcomes problems of production, transport and installation associated with the currently available technology.

Objects of the invention:

An object of the present invention is to provide a low cost and high quality system for treatment of sewage waste for on-site sanitation.

Another object of the present invention is to allow mass production of the system by rotational molding and similar techniques from lightweight materials. Yet, another object of the present invention is to reduce the space occupied by the system for trouble-free transport.

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 schematic diagram of a system of treatment of sewage waste for on-site sanitation, in accordance with the present invention;

Figures 2, 3, 4 5 and 6 show various embodiments of the system of the treatment of the sewage waste for on-site sanitation, in accordance with the present invention; and Figure 7, 8, and 9 shows graphs of material Vs void ratio, material Vs total solid removal and material Vs COD removal using the system of the present invention. Summary of the invention

Accordingly, the present invention provides a system for treatment of sewage waste for on-site sanitation. The system comprises a tank configured below ground level with outer surface of the tank filled with soil. The tank includes a plurality of holes configured on sides thereof to allow liquid flow out into the surrounding soil. Further, the system comprises at least one lid covering the tank. The lid is secured to the tank with an air gap around a perimeter of the lid. Furthermore, the system comprises an inlet pipe connected to the tank for supplying sewage waste thereto. Moreover, the system comprises a worm bed configured within the tank. Specifically, the worm bed acts as a primary filter. Also, the system comprises a filter bed arranged in the tank beneath the worm bed, the filter bed comprising at least three layers of drainage media acting as secondary filters. Specifically, the top layer includes smaller voids and the bottom layer includes larger voids.

Detailed description of the embodiments:

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

The present invention provides a system of treatment of sewage waste for on-site sanitation. The system is a low cost and high quality system for treatment of sewage waste for on-site sanitation. Mass production of the system is possible by rotational molding and similar techniques from lightweight materials. The space occupied by the system is less for trouble- free transport. 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 brackets in the following description. Referring to figure 1, a system of treatment of sewage waste for on-site sanitation (100) (hereinafter referred as "the system (100)") in accordance with the present invention is shown.

The system (100) comprises of a tank (50) with a lid (30). The tank (100) is assembled below the ground level (10). The space around the outer surface of the tank is filled with soil (20). In an embodiment, the tank (50) can be made from materials selected form fiberglass, plastic, including recycled plastic and like. The tank (50) can be manufactured by methods including but are not limited to, rotational moulding, other precast process and like. In the embodiment, the tank (50) may be circular, rectangular or square in shape. The tank (50) may be as a single part of be in more than one part with simple fastenings to join the parts together when assembled. The sides of the tank (50) may be perforated with plurality of holes of any size to allow liquid flow out into the surrounding soil so long as the strength of the tank (50) is maintained.

In the embodiment, the lid (30) may be made from similar materials to the tank (50). In a preferred embodiment, the lid (30) is a single piece to ensure the system (100) is watertight. An inlet pipe (40) is connected from one side of the tank (50) for supplying sewage waste to the tank (50). In another embodiment; the inlet pipe (40) may be made connected to the centre of the lid (30). In yet another embodiment, the inlet pipe (40) may be made connected to any one side of the lid (30). In the preferred embodiment, the weight of the tank (50) and the lid (30) should not be more than 20Kg. The lid (30) should be strong enough to support 2-3 people and should be securely fastened to allow an air gap around a perimeter of the lid (30). In assembled condition, the system (100) is capable of treating the waste from a typical family of five people. The tank (50) consists of a worm bed (60) that acts as a primary filter. In the embodiment, there should be a headspace of at least 35 cm above the worm bed (60). A waste digestion occurs in and above the worm bed (60). The worm bed (60) is made from any material that is (a) suitable and known to provide a good environment for worm behavior, health and propagation and (b) able to act as a primary filter and trap the majority of faecal solids and (c) be sufficiently porous to allow good drainage and free movement of worms. In the embodiment, the suitable materials include but are not limited to compost, word chip, coir, mixtures of the same and like. A surface area of the worm bed (60) is of around 0.7 sq m per family.

The tank (50) further consists of a filter bed (not numbered) arranged beneath the worm bed (60). The filter bed consists of layers of drainage media (70, 80, 90) acting as secondary filters. The layers of drainage media (70, 80, and 90) are made from any materials with suitable surface, structural and drainage characteristics for effluent treatment. A gradation in void dimensions from top to bottom, with top being the smallest and bottom the largest, may be provided. In the embodiment, the layers of drainage media (70, 80, 90) can be provided separately or as an integrated unit. In a preferred embodiment, if the layers of drainage media (70, 80, 90) are provided separately, the layers (70, 80, 90) can be added at the time of installation or may be contained by some means, ideally in way that allows for ease of shipment and assembly such as trays, boxes and like. A total void capacity of the filter bed below the worm bed (60) is of at least 200 litres. The base layer (90) of the filter bed has sufficient mechanical strength to support the system (100). The layers of drainage media (70, 80, 90) are made from any materials that provide suitable drainage capacity include but are not limited to coir, sand, gravel, stones, aggregate, lightweight concrete or aggregate replacements such as fly-ash based materials, foam or aerated concrete, porous materials, ceramics, shredded tyres, cement coated- polymeric foam, rubber, different types and configurations of plastic, including bioballs, and glass. The filter bed properties can also be provided by a suitable arrangement of plastic plates, strips, mesh or blocks to create the desired void dimensions and capacity. In the embodiment, the worm bed (60) and filter bed can be assembled in different configurations by maintaining the surface area and void capacity requirements.

In an embodiment, the system (100) includes layers of mesh placed between one or all of the layers, and around any holes in the tank (50) to prevent rodents and other vermin entering the system (100) from the surrounding soil.

Referring to figure 2, a system (100A) in accordance with an embodiment of the present invention is shown. In this embodiment, the tank (50A) is a funnel type container with perforation. The other configuration of the system (100A) is similar to system (100) and hence not described herein in detail for brevity of the invention.

Referring to figure 3, a system (100B) in accordance with another embodiment of the present invention is shown. In this embodiment, the tank (50B) consists of three separate containers having perforation (45B). The other configuration of the system (100B) is similar to system (100] and hence not described herein in detail for brevity of the invention.

Referring to figure 4, a system (lOOC) in accordance with yet another embodiment of the present invention is shown. In this embodiment, the base layer (90C) of the filter bed consists of a tube/plate settler arrangement. The other configuration of the system (lOOC) is similar to system (100) and hence not described herein in detail for brevity of the invention.

Referring to figure 5, a system (100D) in accordance with still further embodiment of the present invention is shown. The system (100) is designed to weigh as little as possible and to take up as little space as possible, and be quick to unload and install at the site.

Referring to figure 6, a system (100E) is shown in accordance with yet another embodiment of the present invention. In this embodiment, a circular tank (50E) is made in two parts that are lightweight, take up less space for shipment than a single piece tank of equivalent volume by placing one part alongside the other, and can be easily and securely assembled at the site. In further embodiments, the tank (50E) can also be of different shapes such as square or rectangular but use the same principle for packing and assembly. In such embodiments, some framing at the corners will aid stability. The other configuration of the system (100E) is similar to system (100) and hence not described herein in detail for brevity of the invention.

Examples

The table below shows the properties of four alternative drainage media of the system (100) that is secondary filtration media used in comparison with the stones used previously. It shows that in each case the densities are considerably less than stones and thus the weight of the resulting filter bed can be reduced by up to 90%.

Specifically, separate filter beds were set up containing each of the above materials so that their performance as drainage media could be compared. In each case the filter beds, comprising these materials at the bottom with a layer of coir on top, were made up in a suitable container and covered with a worm bed. Worms were added and sewage sludge was applied daily for several weeks. The void ratios of the filter beds were measured using standard methods and removal of faecal solids and reduction of COD in the effluent were monitored.

Figure 7 shows a graph of void dimensions of the different drainage media. It can be seen that all the alternatives have similar or larger void ratios. This means that there is potential to reduce the size of the filter bed by using alternative media such as rubber pieces. Figure 8 and 9 shows a graphs of results obtained after 2 weeks and show that in terms of treatment efficiency the alternative media were in many cases superior to stones. These results demonstrate that there is potential to reduce the weight and size of the filter bed and hence the whole treatment system and at the same time improve its treatment efficiency.

Advantages of the invention: 1. The system (100) saves cost compared with structures made from concrete or brick and mortar

2. The system (100) can be made from lighter weight materials and is therefore easier to assemble, transport and install.

3. The maintenance of the system (100) is easier as the different parts are readily removed for cleaning if required.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

Claims

We Claim:

1. A system for treatment of sewage waste for on-site sanitation, the system comprising

a tank configured below ground level with outer surface of the tank in contact with the soil, the tank having plurality of holes configured on sides thereof to allow liquid flow out into the surrounding soil;

at least one lid covering the tank, the lid secured to the tank with an air gap around a perimeter of the lid;

an inlet pipe connected to the tank for supplying sewage waste thereto;

a worm bed configured within the tank, wherein the worm bed acts as a primary filter and suitable environment for worm health; and

a filter bed arranged in the tank beneath the worm bed, the filter bed comprising layers of drainage media acting as a secondary filters, and providing appropriate void volumes.

2. The system as claimed in claim 1, wherein the worm bed is made up of compost, word chip, coir, and combination thereof.

3. The system as claimed in claim 1, wherein the layers of the drainage media are made from coir, sand, gravel, stones, aggregate, lightweight concrete, aggregate replacements such as fly-ash based materials, foam or aerated concrete, porous materials, ceramics, shredded tyres, cement coated- polymeric foam, rubber, different types and configurations of plastic, including bioballs, and glass.

4. The system as claimed in claim 1, wherein the tank comprises a mesh placed between the layers and around any holes in the tank to prevent rodents and other vermin entering the tank.

5. The system as claimed in claim 1, wherein the tank is circular, rectangular or square in shape.