Emergency water treatment in WASH emergency response following cholera outbreak in Zimbabwe [closed]
The WASH Cluster Zimbabwe has following question: Has there been any experience of using copper (cupric ion) as alternative to chlorine in emergencies for water treatment? Specifically a product developed by "Earth Science Laboratories" Earth Tec. which is used in the US and according to its marketers has potential and doesn't taste so bad. (http://cleanwaterfortheplanet.com/potablewater.asp) Do you have any knowledge of experiences in the use of this product?
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close date 2014-02-06 16:29:37.231538
A quick scan on the internet and bookshelf follows
The producers themselves promote the product for pre-treatment not for disinfection – see http://cleanwaterfortheplanet.com/potablewater.asp
Binnie and Kimber in Basic water treatment write about the use of copper sulphate as follows: Algal control is not easy. In the past it was common to control algal blooms by dosing copper sulfate before a bloom occurred. Copper is an algicide and the technique was effective in reducing algal blooms if properly monitored and applied. Copper was dosed at around 0.3 mg/l of copper sulfate. Except in very soft waters the copper was quickly removed by precipitation as copper carbonate. However, despite this, nowadays the dosing of relatively large quan¬tities of copper into the aquatic environment is unacceptable because of its effect on other organisms. Copper sulfate is toxic to fish at a concentration similar to that needed to kill algae and thus fish kills were common. Algal growth is often limited by the availability of phosphorus and thus in smaller reservoirs, or reservoirs storing upland water low in phosphate, it may be practicable to limit algal growth by dosing a ferric salt to precipitate phosphate. However, this is relatively expensive and produces sludge that has to be removed periodically.
WHO’s document on copper in drinking water http://www.who.int/water_sanitation_health/dwq/chemicals/copper.pdf makes specific reference to copper sulfate pentahydrate – a quick reading would make me cautious in its use.
Overall, I would suggest it could be used as a pre-treatment to control algae if algae were the problem but not as disinfection; if used as pre-treatment, the subsequent treatment would need to be designed to remove/reduce the copper content to acceptable levels; final disinfection with chlorine would still be required; concerns about dangerous by products of chlorination are best addressed by designing better treatment than swopping to another disinfectant.
High Test Hypochlorite is available in most supermarkets in Harare again now for use in the many swimming pools of the Sunshine City. You can get large drums of the stuff and there must be a way to get hold of it at wholesale rather than retail prices.
Our water treatment process specialists have the following to say on the query from the field.
Copper is toxic and the health based guideline (WHO) is 2 mg/l and above 5 mg/l it imparts colour and a bitter taste to the water. Metals at low concentrations do limit the growth of bacteria and copper has been used to prevent the growth of algae within raw water reservoirs (this is the application referred to below).
Copper is not a suitable disinfectant for potable water and certainly not a replacement for chlorine.
I have had no experience in using Copper sulphate as an alternative to chlorine for drinking water. I have made enquiries with other engineers at Anglian Water, unfortunately none of them have any experience or knowledge of the product being used in applications here in the UK.
Copper sulphate is widely used as a fungicide to control bacterial and fungal diseases of fruit & vegetables in the farming sector. I know that Copper sulphate, was one of the first methods used to disinfect water, but concerns arose with regards to the toxicity levels at high concentrations. The EPA limit for copper sulphate in drinking water is 1 ppm (1 mg/l). This limit has been set to prevent a disagreeable taste from copper in drinking water, as well as to provide adequate protection from toxicity.
I have done some research on Earth Tec, and they are registered with the US EPA. Their advisory dosage rates results in a maximum of 0.06ppm (0.06 mg/l) of copper, which is acceptable. Although I think it's important to remember that their product is predominantly for Pre-treatment of drinking water, i.e. the control of algae & reduction of bacteria which is good in reducing the overall kill rate, but the water might still require a final disinfectant step (i.e. chlorination etc) before it can be consumed. Tests will have to be done to confirm whether this product is sufficient for disinfection on its own (bearing in mind the restricted dosing rates).
To confirm Tim's email - from personal experience some 10 years ago -copper sulphate was readily available in Zimbabwe and used in for the prevention of growth of green algae in swimming pools (usually used in conjunction with chlorine) but not used as an effective disinfectant in itself ... As Martin confirms - HTH appears to still be available..
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