Page 51 - EATS Case ( B)

Water can carry a wide range of harmful germs, viruses and

protozoa, including salmonella, cholera, hepatitis and
tuberculosis. Chlorine-based chemicals can kill most

pathogens, but some are not so easily dealt with.

Cryptosporidium, in particular, is resistant to chemical

treatment.

“In the last 20-30 years, there have been numerous

technology developments with mercury-based lamps,
including low-pressure high-output, medium-pressure and

low-pressure amalgam lamps,” says Dussert. Depending on

the usage, lamps can range from 4cm to over 200cm in

length, and last up to 12,000 hours. They are generally

mounted in watertight quartz tubing inside stainless steel
reactors. Water is then pumped past the lamps; UV radiation

only takes about three to five seconds to kill most bacteria

and viruses. Units cost from under $1,000 for home modules
3
that treat 0.5m /hr, to $5 million municipal water installations
3
capable of treating 100,000m /hr.

According to Dussert, the cost of chlorination and UV
treatment are roughly equal. “UV capital costs are a little

higher, but operating costs are lower,” he says. “Treatment of

drinking water runs around $0.02-0.05 per 1,000 gallons, and
wastewater $0.10-0.15 per 1,000 gallons.”

In wastewater treatment, UV has an advantage over

chemicals such as chlorine, which can generate by-products
that are toxic to marine life. “The regulations involving the use

of chlorine are evolving,” says Dussert. “There are concerns

with the environment, transport and the potential for
terrorism.”