IE20140128A1 - Rainwater purification system - Google Patents

Abstract

The invention provides for a multistage rainwater purification method to provide potable water comprising: a) collecting rainwater, b) a first flush filter, c) a first collection tank to regulate the flow of water, d) performing a first purification treatment running the water sequentially through a sequence of pre-filters and microbiological purification, e) collecting the water in a harvest tank, f) performing a second purification treatment including electropositive filtration, pH adjustment unit and microbiological purification involving UV disinfection or electropositive filtration, g) a supply tank prior to subsequent use, wherein the water having been treated is recirculated through a UV disinfection unit or electropositive filtration unit at both the harvest tank and the supply tank to maintain water quality, and further by introducing an appropriate volume of chlorinated water from a public water supply to the treated water in the harvest tank. The invention also provides an apparatus to perform the method described.

Description

The present invention relates to the purification of rainwater.

Background to the Invention Irish Patent No. IES85985 describes a three phase purification/sterilisation system. Following harvesting, rainwater is passed through a 5 micron pleated sediment filter and then feeds through an electro-positive filter which is the final phase of filtration. It then passes through an ultraviolet steriliser. The above invention describes the purification of rainwater to remove 99% of viruses and bacteria without the use of chemicals.

Rainwater always contains dissolved minerals, chemical poliutants and pathogenic organisms that it may have come in contact with when falling as rain and in the harvesting process. The purification system in IES85985 required to be extended to include additional purification processes and consequently this new invention uses an enhanced combination of technologies to provide potable water.

This invention effectively kills or removes bacteria/viruses and cysts from rainwater. It also removes suspended solids, natural organic matter, chemical pollutants, minerals and salts.

The combination of coagulation, flocculation, sedimentation, multistep filtration including activated carbon filtration, sand filtration, bag filtration, pleated sediment filtration, UV sterilisation, deionisation, reverse osmosis treatment, pH neutralisation and ultrafiltration provides both bacterial/viral free and contaminant free water suitable for 98% of all domestic, commercial and agricultural operations.

Summary of Invention This invention of rainwater purification involves the removal of suspended particles, viruses/bacteria, parasites, cysts such as Giardia and Cryptosporidium, organic matter, dissolved metals and salts that may be present in rainwater.

According to the Invention there is provided a rainwater purification system, comprising the following: A A pre-treatment 1st flush system and fittings B A post-first flush collection tank, to govern the flow of water through the system C A coagulation, flocculation and sediment filtration treatment unit D A sand filter/bag filter E An activated carbon filtration unit F An ozonation treatment unit G Α 1-25μ pleated cartridge filtration unit H A harvest tank, to collect rainwater from run-off area, typically the roof of the building in which the system is housed, after pretreatment by means of any or all of A-G J An electropositive filtration unit K A reverse osmosis treatment unit L A pH neutralisation unit M A deionisation unit N An ultrafiltration unit P A UV sterilisation unit Q The header tank in the building being supplied with treated potable water after pre-treatment by means of any or all of J-P R The main body of the building being supplied with treated potable water S A recirculation loop, whereby treated water maybe recirculated into the system to maintain its potability Brief Description of the Drawings The rainwater purification system according to this invention will be more clearly understood from the following detailed description of an embodiment thereof, given by way of example only, with reference to the accompanying Fig. 1 which illustrates a system of the invention.

Detailed Description of the Drawings Referring to Fig. 1, rainwater from a run-off area, typically the roof of the building to be supplied with potable water, enters the system at (A}, a 1st flush system to remove leaves, debris and other large scale Impurities before the filtration process. The water may then proceed to a first collection tank (B) which regulates the flow of water to be treated into the system.

The water then goes through coagulation, flocculation and sedimentation treatment (C). Coagulation is effected with the use of coagulating agents such as alum and/or polymers. Flocculation follows coagulation and involves a mixing technique which facilitates the aggregation of particles which become heavy and sink in a sedimentation process. This removes natural organic matter, colloids and some of the viruses and bacteria which may be present. A maximum flow pleated sediment filter removes the sediment before the water goes to the next treatment stage. The sediment filter cartridge and casing is washable and reusable. It is typically 1-25μ in grading, though other grades may be used in particular cases to suit the circumstances. It removes coarse particles and washed-in plant matter.

The water then proceeds through a number of filtration/treatment steps as follows: a sand/bag filtration step to remove algae and suspended material (D), activated carbon filtration (E) to remove contaminants, especially organic compounds, by chemical absorption, ozonolysis (F) to kill parasites, bacteria, fungi, viruses, algae while leaving no residual disinfectant in the treated water, and a second 1-25μ pleated filtration to remove particles of iron and manganese which may be introduced at the ozonolysis.

This pre-treated water is then fed into a harvest tank (H), which stores the water before the second treatment regime. The harvest tank includes a recirculation loop (S), to maintain the sterility of the treated water by means of a UV sterilisation unit (P).

Chlorinated water (generally from the mains supply) is then added to the treated water in the harvest tank in the proportion of 25% by volume of the tank to help maintain quality and to insure against any prolonged period without rain.

The water in the harvest tank is suitable for supplying toilets or irrigation systems, but is not yet in a potable state. Thus, this water may be subjected to a second treatment to render it potable.

Water from the harvest tank is fed first to an electropositive filtration unit (J) which removes 99% of all viruses and bacteria. Electropositive filters are known in the art to retain submicron particles effectively. The filters have high particulate capacity and resist clogging by small particles and are robust and fault tolerable. The filter cartridge used is rated 1μ absolute, and meets or exceeds the 99.9% efficiency requirement established by the Water Quality Association to reduce Cryptosporidium and Giardia cysts from drinking water.

The water then proceeds to a reverse osmosis system (K) to remove metals, metal salts, bacteria, viruses and parasites, a pH neutraliser (L) to prevent corrosion in metal pipes in the building's plumbing and to improve potability. Rainwater, depending on harvesting location, can have a natural pH as low as 4.

An ion exchange treatment (M) then ameliorates water hardness following neutralisation and removes any anions or cations remaining in solution after the reverse osmosis treatment, after which an ultrafiltration membrane filter removes any remaining viruses, bacteria, colloidal particles and/or organic molecules.

An ultrafiltration unit (N) is then used to remove viruses, bacteria, colloidal particles and other organic molecules.

This treated water is then stored in the building's header tank, where a second recirculation loop (S') facilitates UV sterilisation (P'), to maintain the sterility of the treated water prior to use.

Variations in the above described embodiment may be envisaged, depending on the circumstances, such as the initial state of the rainwater to be treated, the amount of recirculation prior to use, the volume of water required and the final use to which the treated water is put.

For instance, it may not always be necessary to employ ozonolysis, in which case, the second microfiltration step (G) would also not be necessary.

Equally, if water is not required to be potable, the reverse osmosis step or others in the second phase of treatment may not be necessary.

Claims (3)

1. Claims 1. A rainwater purification method to provide potable water comprising: a) collecting rainwater from a suitable run-off area, b) using a first flush filter to remove large scale impurities, c) collecting the water in a first collection tank to regulate the flow of water through the system, d) performing a first purification treatment running the water sequentially through a coagulation, flocculation and sediment filtration unit, a sand/bag filter unit, an activated carbon filter unit, an ozonolysis unit, a second activated carbon filter unit and a first UV sterilisation unit, e) collecting the water in a harvest tank prior to further treatment, f) performing a second purification treatment running the harvested water sequentially through an electropositive filtration unit and a reverse osmosis unit, pH adjusting the water to within the range of pH 6.5-9.5, deionising the pH adjusted water, and performing a second UV sterilisation on the treated water, g) collecting the fully treated water in a header tank prior to subsequent use, wherein the water having been treated is recirculated through a UV sterilisation unit at both the harvest tank and the header tank to maintain water quality, and further by introducing 25% by voiume of chlorinated water from a standard water supply to the treated water in the harvest tank.
2. 2. The method as claimed in claim 1, wherein in the second purification treatment, the reverse osmosis treatment is omitted and an ultrafiltration step is added before the second UV sterilisation.
3. 3. A rainwater purification method as described in Claims 1 or 2 omitting the deionisation step. 6. 7. 8. 9. The rainwater purification method of any preceding claim wherein in the first purification treatment the ozonolysis and second active carbon filtration treatments are omitted. The method of any preceding claim wherein 99% of coliforms, bacteria, cysts and Cryptosporidium are killed off/removed from the water to be treated. The method of any preceding claim wherein sediment and particulate matter down to 1μ in diameter is removed from the water to be treated. A method for purifying rainwater comprising: a) collecting rainwater from a suitable run-off area, b) using a first flush filter to remove large scale impurities, c) collecting the water in a first collection tank to regulate the flow of water through the system, d) running the water sequentially through a coagulation, flocculation and sediment filtration unit, a sand/bag filter unit, an activated carbon filter unit, an ozonolysis unit, a second activated carbon filter unit and a UV sterilisation unit, e) collecting the water in a harvest tank prior to further treatment, wherein the water having been treated is recirculated through a UV sterilisation unit at the harvest tank to maintain water quality, and further by introducing 25% by volume of chlorinated water from a standard water supply to the treated water in the harvest tank. The rainwater purification method of claim 7 wherein the ozonolysis and second active carbon filtration treatments are omitted. A method according to any preceding claim wherein any activated carbon filter is rated at 1μ absolute. 10. An apparatus for purifying rainwater, the apparatus comprising; 11. a) a first flush filter to remove large scale impurities, b) a first collection tank to regulate the flow of water through the system, c) a coagulation, flocculation and sediment filtration unit, d) a sand/bag filter unit, e) a first activated carbon filter unit, f) an ozonolysis unit, g) a second activated carbon filter unit h) a first UV sterilisation unit, i) a harvest tank for holding treated water prior to further treatment, j) an electropositive filtration unit k) a reverse osmosis unit, l) a pH neutraliser capable of adjusting the pH of any treated water to within the range of pH 6.5-9.5, m) a deioniser n) a second UV sterilisation unit, o) a header tank to receive and store the treated water, p) a first recirculation loop in the harvest tank, to run any stored water through the first UV sterilisation unit to maintain water quality, q) a second recirculation loop to run the fully treated water through the second UV sterilisation unit to maintain water potability, and r) means for introducing chlorinated water from a standard water supply to the treated water in the harvest tank. The apparatus as claimed in claim 10, the reverse osmosis treatment is omitted and an ultrafiltration treatment unit is added before the second UV steriliser. 30 12. The apparatus as claimed in Ciaims 10 or 11 omitting the deioniser. 13. The apparatus of any of claims 10 to 12 wherein the ozonolysis and second active carbon filtration units are omitted. The apparatus of any of claims 10 to 13 which are capable of killing off of removing 99% of coliforms, bacteria, cysts and Cryptosporidium from the water to be treated. The apparatus of any of claims 10 to 14 which are capable of removing sediment and particulate matter down to 1μ in diameter from the water to be treated. An apparatus for purifying rainwater comprising: a) a first flush filter to remove large scale impurities, b) a first collection tank to regulate the flow of water through the system, c) a coagulation, flocculation and sediment filtration unit, d) a sand/bag filter unit, e) a first activated carbon filter unit, f) an ozonolysis unit, g) a second activated carbon filter unit h) a UV sterilisation unit, i) a harvest tank for holding treated water prior to use, j) a recirculation loop in the harvest tank, to run any stored water through the UV sterilisation unit to maintain water quality, k) means for introducing chlorinated water from a standard water supply to the treated water in the harvest tank. The apparatus of claim 16 wherein the ozonolysis and second active carbon filtration units are omitted. An apparatus according to any of claims 10 to 17 wherein any activated carbon filter is rated at 1μ absolute.