:: Regulatory Requirements::

There are significant regulatory requirements, which govern the continued usage of disinfectants in the USA. These requirements all hinge around the safety of application of the disinfectant; the toxicity to humans and the environment of the disinfectant and the toxicity of the Disinfectant By Products (DBP). These factors then govern the level at which a disinfectant may be used and at what levels it can be discharged. The latest EPA document on Disinfection By-Products (DBP) research of 2003 shows that chlorine dioxide produces the fewest DBP and that these cause the least long term problems to humans.

We will very briefly review the situation for each of the main disinfectants allowed in drinking water.
CHLORINE:
a) dangerous and hazardous to apply and handle gaseous chlorine
b) discharge limits set at 0.025 mg / l to 0.25 mg/ l and continually being lowered
c) major DBP are THM’s; HAA’s; chlorinated organics; oestrogen mimics; endocrine interceptors
d) creates taste, odour and taint problems.
e) Low capital cost and operating cost to use gaseous chlorine

More countries and companies around the world are moving away from gaseous chlorine and indeed in the Food & Beverage Industry particularly in meat and poultry the EU has banned, as of 1 May 2001,  the use of “ super chlorination > 75 ppm “ in light of the DBP and ever more severe discharge regulations.
Since 9/11, the water plants in the USA and select EU countries have undertaken strict review of gaseous chlorine handling facilities as they now become a terrorist target which could have dire consequences for the community in the vicinity of such installations. These facilities need to have extra strong buildings housing significant gas scrubbing capabilities. Furthermore these facilities spend an inordinate amount of time and money on emergency incident planning. This has now increased the cost of handling gaseous chlorine significantly.

CHLORAMINES
a) dangerous and hazardous to apply and handle both gaseous chlorine and gaseous ammonia
b) discharge limits remain for chlorine but chloramines are not as toxic to the aquatic environment and / or normal environment
c) DBP are similar to chlorine but at a lower level
d) Higher capital and operating costs because of gaseous chlorine and ammonia.

The chloramines residual is longer lasting than chlorine so more countries are moving towards chloramines with multi-barrier disinfection technologies viz ozone + chloramines; UV + chloramines; chloramines and chlorine dioxide.

OZONE
a) dangerous to humans but in well designed units generally not a problem
b) ozone residual lifespan is measured in seconds to minutes
c) it was considered at one point to be the “silver bullet” but as DBP become increasingly under the spotlight so too did the problems with ozone emerge. Firstly, ozone is a net producer of THM’s; secondly the DBP found were aldehydes, which are carcinogens and thirdly bromides are oxidised to bromates. Bromates are now regulated at 1to 5 parts per billion (1-5ppb) !!
d) Very high capital costs and operating costs are put at similar levels to chlorine ---- see WRC Report 1030/1/03.

It should be stated clearly that in drinking water plants the only acceptable method of ozone manufacture is from oxygen as the precursor. If one uses air as the precursor then 3 times the quantity of ozone produced is in the form of NOx’s, which are also carcinogens.
As for chlorine, the safety of generation of ozone has become a critical issue particularly to the potential for ozone leaks, which can be fatal to humans at levels as low as 4 ppm in air.

ULTRA VIOLET LIGHT (UV)
UV has many positive aspects to its potential as a disinfectant, however, in potable water plants with any type of distribution system it has no lasting residual, which basically reduces its use to zero. UV can be used in conjunction with a product that has a lasting residual like chlorine, chloramines or chlorine dioxide.
a) not dangerous to produce or apply
b) no discharge problems
c) DBP from UV are generally nitrites, which are typically regulated to 1 ppm
d) low capital cost but high maintenance costs because bulb life expectancy is limited to a finite number of hours and biofilm can grow across the UV lights which will then significantly reduce its efficacy.

CHLORINE DIOXIDE
The EPA comment ( personal communication, 2002 ) was that chlorine dioxide will become as important to the world in the next 20 years in the same way that chlorine was important for the last 100 years.
The level of visibility of chlorine dioxide has been immeasurably strengthened by its adoption by the EPA as the technology for the bioremediation of the various government and civilian buildings, which experienced the “anthrax letters “ attack in October 2001. Our one technology partner SABRE is the service provider to the EPA of chlorine dioxide technology.
The evolution of simple and cost effective chlorine dioxide generators has resulted in more countries and companies embracing this technology as an alternative to chlorine or to use it in combination with ozone and / or UV.
new generators are not hazardous to produce or apply
discharge problems have not surfaced because there are means of reducing chlorite to below aquatic toxicity levels
DBP of concern is largely chlorite but with the emergence of chlorite reduction technologies this problem is rapidly being reduced. Chlorate is a DBP but its MCL’s and toxicity levels are much lower ( considered non-toxic) in comparison to chlorite. [Chlorate is non toxic to Daphnia ].
Low to medium capital cost and running costs which can match gaseous chlorine levels.