Cryptosporidium and Giardia lamblia

You may have heard in the news about Cryptosporidiosis and Giardiasis outbreaks in a number of regions within the United Kingdom. Both of the organisms involved are pathogenic and can be waterborne.

Long recognised as a parasite of animals, cryptosporidium has only recently been shown to cause illness in humans. Research is still continuing; this information sheet is compiled from present available knowledge.

Infection by Cryptosporidium and Giardia is fairly rare in people. It normally originates with infected farm animals and can be transmitted from one person to another. The symptoms in human beings are usually severe stomach cramps, sickness and diarrhoea, nausea, fatigue and weight loss. The incubation period is from 7 to 14 days and the illness can last from two weeks onwards depending on vulnerability. Patients with certain chronic conditions and children are at higher risk.

Cryptosporidium organisms (protozoa) form protective oocysts between 4 to 7 microns in size. Giardia are also in the form of oocysts but slightly larger, between 6 to 10 microns in size. (One micron is one thousandth of a millimetre). This allows them to survive outside the body of the host, in a watercourse, and protects them against disinfection methods such as chlorination or ultra-violet radiation.

Cryptosporidium is not killed by normal chlorination and is only made harmless by long exposure to concentrated ultra violet light or specialised chemical treatment, Giardia is killed by long contact with chlorine or long exposure to concentrated UV light. However the most successful method of removing oocysts from a water supply is by filtration through microstrainers or cartridge filters.

These oocysts are found in surface waters e.g. rivers, streams and some springs. It is unusual to find them in borehole or deep well waters unless there are fissures allowing surface waters into the source.

Occurrence is usually seasonal, normally found after heavy rainfall in the spring and autumn when animal faeces are flushed into watercourses.

Water Quality Definitions

Herbicides and Pesticides

The 1993 World Health Organisation guideline values for drinking water lists a whole series of pesticides with maximum permissable limits in drinking water.

The number of different pesticides available and the amount used in improving agricultural yields have significantly increased over the past 40 years.

It is known that most surface derived and ground waters contain some pesticide residues in the range of 0.001 to 0.1 �g/l (�g/l = microgrammes per litre). These concentrations are very small and result from the legitimate use in the community.

The analysis for these pollutants is very expensive due to the highly technical equipment necessary.

The current standards are:

Individual substances 0.1 �g/l

Total substances 0.5 �g/l

These values were chosen mainly on the limits of detection of the analytical equipment than on any known information on toxicity to human beings.

�Safe� herbicides and pesticides are mainly so called because of their very short active life once exposed to the atmosphere or day/sunlight, they degrade very quickly. However if they are degraded by natural ultraviolet light, after they enter the ground they do not degrade and eventually are deposited in underground water - aquifers and reservoirs. They have been found in deep borehole waters.

To be safe, there are barriers/reduction/adsorption materials commonly available and an adsorption column is recommended to be included in any private supply system.

The adsorption material is usually contained in a disposable or refillable cartridge fitted inside a small filter housing, which becomes an integral part of a private supply system.

Taste, Odour and Appearance

The human senses of taste and smell are stimulated by a myriad of chemical compounds, both organic and inorganic. Certain of these compounds may be found in private water supplies, and more than any other factor they influence the palatability of the water.

Another important aspect is appearance of the water, it must be at least clear to be palatable.

Some common pollutants found in wells, springs, and boreholes which manifest themselves are:

Naturally occurring algae

These range from grassy, fishy, cucumber, musty, spicy and septic odours having sweet to bitter tastes and leave a dry or metallic taste on the tongue.

Typical colours are green, blue/green to brown and will sometimes produce a film on the surface looking similar to oil.

Manganese

This is very abundant in rocks and soils, it is essential for nutrition in both plants and animals. However at high levels of 200 to 400 �g/l will impart an unpleasant musty/farm taste and can foster the growth of micro-organisms which will produce secondary tastes such as pond-like or earthy.

At concentrations of 500 �g/l the appearance of the water will be affected. When allowed to come into contact with oxygen from the atmosphere manganese will oxidise changing the colour of the water from clear to grey/brown cloudy.

Iron

This is commonly found, sometimes in the presence of manganese, its characteristics are very similar to manganese, the taste is dry and metallic, but when oxidised it will usually produce suspended particles of iron oxide (rust) which are orange/brown in colour.

Copper:

If acidic water is passed through copper plumbing, copper is dissolved, imparting a distinctive blue colour. With domestic soap, insoluble copper soaps may be formed, leaving blue/green deposits.

Sulphide and sulphate:

The most common reasons for Sulphide and Sulphate in ground waters in the United Kingdom are the natural processes of organic decomposition and bacterial activity.

However, at low pH levels, this can produce hydrogen sulphide, which has a distinctive rotten eggs odour. Sulphate over 1000 mg/l can exert a laxative effect.

Taste Odour and Appearance (Chart)

Private Water Supplies

The legislation which covers private water supplies is:

THE PRIVATE WATER SUPPLIES REGULATIONS 1991

In essence the act states that the quality of private water supplies must comply with the quality of water supplied by all water companies within the United Kingdom.

The act states that any water supplied for domestic purposes, drinking, cooking or washing must not contain any element, organism or substance that would be detrimental to public health.

However, some parameter limits may be relaxed by your local Environmental Health Department provided that there is no risk to health.

If you supply water to guests or customers you must ensure that the quality is within the regulations limits, if it is not, you must advise your guests and customers that the water is not drinking water, a clear notice by the taps is usually the best method.

If the water is also unfit for washing and cooking you must advise them.

This small insurance will protect you, your guests or customers.

This act does not just cost someone with a private water supply more money or involve them in red tape, it is an essential health safeguard.

Most waterborne diseases will not just affect one person but all people using the same supply.

Manganese

Manganese (Mn) The Water Supply Regulations limit is 0.050 mg/l or 50 �g/l.

Manganese is too reactive a metal to be found in elemental form in nature but its ore, the black dioxide pyrolusite, is widely distributed. The purified metal or its salts are used extensively in industry for the manufacture of glass, ceramics, batteries, paints, varnishes, inks, dyes and fireworks.

It occurs in two forms (divalent and trivalent). Although the chlorides, nitrates, and sulphates are soluble in water, the oxides, carbonates and hydroxides are only sparingly soluble and manganese is rarely found in natural surface waters in concentrations above 1.0 mg/l or 1000 �g/l. However, in ground waters subject to reducing conditions manganese can be leached from the soil and occur in high concentrations. Manganese often accompanies iron in ground waters.

At high concentrations in water it will cause; an unpleasant taste, deposits on food during cooking, stains on sanitary ware, discolouration of laundry, deposits on plumbing fittings and cooking utensils, and will foster the growth of micro-organisms in water supply systems.

Manganese is commonly found dissolved in borehole waters, and at first glance, fresh from the pump, the water may appear crystal clear. However, after it has come in contact with oxygen in the air it will oxidise into an oxide of manganese and deposit visible solid particles or coat exposed surfaces.

There are treatment methods to remove dissolved manganese from water supplies, powerful oxidants such as chlorine will cause oxidation and the production of particles that may be filtered out.

For private water supplies chemical addition is not always practical or recommended and a well established method of removal is by apparent adsorption onto manganese dioxide. A manganese dioxide mixture or similar is retained within a filtration vessel, the water to be treated is passed through a column of the media and manganese levels are reduced. After a period of operation the column is automatically backwashed to flush off the deposited manganese particles and the process can continue.

pH level is very important in the process of manganese oxidation and removal. It is usual for borehole waters to contain high levels of carbon dioxide and consequently carbonic acid; this may depress the pH below the optimum range for manganese removal. CO2 removal must be addressed before manganese removal can take place.

IRON

Iron (Fe) The Water Supply Regulations limit is 0.200 mg/l or 200 �g/l.

Iron is a common metal that is found as ore and is widely distributed. It is corroded by water in the presence of oxygen. With acid waters iron is soluble and is leached from iron bearing rock.

Iron is found in surface waters and commonly found dissolved in borehole waters; at first glance, fresh from the pump, the water may appear crystal clear. However, after it has come in contact with oxygen in the air it will oxidise into iron oxide (rust) and appear as visible solid particles causing the water to colour orange/brown. After a time the particles will tend to agglomerate and settle.

A simple test for iron is to take two clean identical bottles, run the borehole/supply pump for a while, quickly fill one bottle to the brim and tighten the lid. Fill the second bottle to half full and secure the lid. Vigorously shake the half full bottle, remove its lid, leave to stand and compare the colour of the two bottles. If you can notice a difference, it is very likely there is iron dissolved in the water.

Iron has very similar characteristics to manganese, but is more readily oxidised. It will cause orange/brown staining on sanitary ware, laundry and other places such as where there is a leaking tap - large stains will occur. Iron oxides will deposit on the internal surfaces of water pipes producing a brown deposit. It has a very low taste threshold, if you can see it, you can probably sense a dry metallic taste.

There are treatment methods to remove dissolved iron from water supplies, powerful oxidants such as chlorine will cause oxidation and the production of particles that may be filtered out. For private water supplies chemical addition is not always practical or recommended. As iron is readily oxidised, aeration is effective.

Another well established method of removal is by apparent adsorption onto manganese dioxide. A manganese dioxide mixture or similar is retained within a filtration vessel, the water to be treated is passed through a column of the media and iron levels are reduced. After a period of operation the column is automatically backwashed to flush off the deposited iron oxide particles and the process can continue.

pH level is important in the process of iron oxidation and removal. It is usual for borehole waters to contain high levels of carbon dioxide and consequently carbonic acid which may depress the pH to below the optimum range for iron removal. CO2 removal must be addressed before iron removal can take place.

Nitrogen, Ammonia, Nitrite and Nitrate