GB2315427A

GB2315427A - Waterborne parasite filter

Info

Publication number: GB2315427A
Application number: GB9615263A
Authority: GB
Inventors: Edward A Gardyne; Edward D Garoyne
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-07-20
Filing date: 1996-07-20
Publication date: 1998-02-04
Also published as: GB9615263D0

Abstract

A filter for removing waterborne parasites uses a sintered stainless steel filter member preferably of 1 to 3 micrometre pore size. Preferably the filter is a cylinder of sintered material having a male thread at one end and a blanc disc at the other which is screwed into the inlet end of a two part, threaded housing. The other part preferably has an outlet and a domed end. The housing can be of stainless steel or plastic such as uPVC. The filter can be removed for cleaning or cleaned by an internal brush rotated by an external electric motor and/or backwashed either periodically or automatically.

Description

DURABLE FILTER / BARRIER TO WATERBORNE PARASITES This invention relates to a durable filter! barrier to waterbome parasites.

Cryptosporidium Parvum oocysts and Giardia Lamblia cysts are parasites which are both known to infect human beings via the water borne route, i.e. potable water used for drinking, cullinary, food and drink manufacture purposes.

Both of these parasites are extremely robust and durable in nature, and are both of a small size.

(Giardia approx 12 micrometers & Crypto approx 5 micrometers across) Ingestion of these parasites by human beings can lead to serious and long lasting illness especially in the young, elderly, and immuno-compromised. Currently effective drugs are available to treat individuals infected with the Giardia cyst, (Giardiasis) however there is no effective drug treatment at present for individuals infected with the Cryptosporidium cyst, (Crytosporidiosis). ( Crytosporidiosis).

Both cysts are therefore of great concern to water treatment industry professionals, researchers , public health professionals and regulators.

Certain cases of cryptosporidiosis and giardiasis have been attributed to treated water supplies, indicating that on occasions conventional means of water treatment cannot guarantee the blockage and/or destruction of these cysts. For instance the use of chlorine for the disinfection of water is almost universal yet both of these cysts are insensitive to its action even when subjected to high concentrations.

Widespread contamination of surface waters with one or both of these cysts has been reported throughout Europe, the United States, Canada and the Far East i.e. concern is worldwide. At present the only effective advice that can be given by public health officials to consumers in an effected area is to boil the water before use or to fit a suitable filter / barrier at the point of water supply use. Filter! barrier elements manufactured in a range of different materials are in use for this purpose, however these invariably require regular complete replacement when they become fouled following a period of use. In addition if fouled elements are not replaced expeditiously, the filter / barrier may break down causing release of dangerous pathogens into a water supply intended for human consumption.

The element itself may also become a breeding ground for parasites, bacteria, viruses and other water borne organisms.According to the present invention there is provided a durable filter / barrier comprising an external housing to contain and support an internally mounted filter / barrier element, means to uncouple the external housing using a hand screwed break coupling and allow access to the internal filter element which may also be unscrewed and detached completely from the external housing. The filter/ barrier element is manufactured in sintered stainless steel material conferring strength and durability with no possibility of element deformation, integrity failure or breakthrough even when it becomes completely fouled and blocked. The material used is inert and will not of itself degrade or contaminate the water. All materials used in the overall constuction of the unit are in compliance with regulations 25 & 26 of 'The Water Supply (Water Quality) (Scotland) Regulations 1990 and 1991 amendments.

Once fouled the filter element may be regenerated using various methods of cleaning which may be applied either singly or in combination. These include boiling, brushing, reverse backwash using clean water, reverse air flow under pressure, steam purging or use of ultrasonic cleaning fluids or hypochlorite based disinfectants. Filter elements may be removed from the external housing for cleaning but depending on the application and/or material used to construct the external housing, cleaning may be carried out in situ, and initiated either manually or automatically. Once cleaned the filter element may then be reused and put back into service.

A specific embodiment of the invention will now be described by way of one example.

The external housing consists of a strong, dark grey in colour u PVC (poly vinyl chloride ) assembly, comprising central pipe section with domed end cap at one end complete with B.S.P.(F) thread, this acting as the outlet of the unit. At the inlet end, a uPVC machined boss fitted internally to a break coupling complete with 'O'ring seal is included allowing this part of the unit to be unscrewed by hand and detached from the outlet end. The inlet part also incorporates the inlet B.S.P.(F) thread and internally supports the screwed filter element. The external physical dimensions of the unit are dependent on the size of the internal filter element which in turn is dictated by the duty flow requirements. i.e. the dimensions of the unit are not fixed and are therefore not specified exclusively in this document. For information only, a unit capable of filtering 12 litres per minute measures 250 mm long by 95 mm in diameter with 20mm diameter hose fittings.

The internal filter element consists of a detachable sintered stainless steel cylinder element with a male B.S.P. thread and 'O'ring seal at one end and a sealed blank stainless steel end cap at the other end.

The grade of sintered stainless steel used is 31 6L, however the unit may be constructed in the grade of sintered stainless steel most suited to the chemical composition of the water to be treated.

The sintered stainless steel material acts as a filter of nominal pore size in the range 1-3 micrometers allowing passage of water under pressure across its structure but blocking the transit of the parasites through the material.

The physical dimensions of the sintered steel filter element is dependent on the filtration surface area requirement which in turn is dictated by the required flow throughput i.e.the dimensions of the filter element are not fixed and therefore not specified exclusively.

For information only a unit capable of filtering 12 litres per minute measures 95 mm L by 43 mm diameter and has a 20mm diameter end thread.

Claims

1. A durable filter / barrier to waterbome parasites comprising an external housing which can be screwed apart to gain access to an intemal sintered stainless steel filter element which may be removed completely for cleaning.. The size of the external housing and filter element to be dependent on the duty flow requirements.The grade of sintered stainless steel used will depend on the chemical qualities of the water to be treated. For the parasites described a filter element in the range 1-3 micrometers pore size is specified.

2. A durable filter / barrier as claimed in Claim 1 wherein cleaning may occur in situ via an intemally mounted spiral brush close fitted through the lumen of the filter element, the brush being driven by an external electric motor assembly.

3. A durable filter / barrier as claimed in Claim 1 or Claim 2 wherein the external filter housing may be manufactured in mild steel, stainless steel or any temperature and/or chemical resistant material and where additional means of cleaning may be applied via solenoid valves to isolate the filter element and allow backflush of the element using compressed air and/or clean water and/or high pressure steam and/or boiling water.

4. A durable filter / barrier as claimed in any preceding claim wherein the extemal filter housing is fitted with an integral differential pressure sensor and/or flow monitoring switch to automatically detect fouling of the filter element and initiate a cleaning cycle.

5. A durable filter i barrier as claimed in any preceding claim wherein the cleaning cycle is automatically controlled using a microprocessor based system.

6. A durable filter / barrier as claimed in any preceding claim using sintered stainless steel filter elements with different filtration pore sizes in the range I nanometer to 500 micrometers inclusive, to allow graded filtration of suspended solids, parasites and/or any biological and/or precipitated chemical contaminant.

7. A durable filter / barrier as claimed in any preceding claim using sintered stainless steel elements in a range of different physical shapes to suit particular applications e.g.flat discs / plates spheres, semi-spheres, box shapes and cylinders.