Most of us are aware that the USEPA is using a consensus process to develop new microbial and disinfection byproduct rules. The concept began back in 1992 and is next in a series of new rules being developed is the Interim Enhanced Surface Water Treatment Rule (IESWTR).
Mandated by the 1986 Safe Drinking Water Act, this particular new rule applies to community water systems serving populations over 10,000. For those of you who missed it, the precursor language describing these new standards was published November 3, 1997, in Vol. 62, No. 212 of the Federal Register.
The IESWTR will be promulgated this November and will address Cryptosporidium, but not from an inactivation or disinfection perspective.
What it will do for this ubiquitous parasite is establish an MCLG (Maximum Contamination Level Goal) of zero. An MCLG however is not an enforceable criteria but it does mandate that either an MCL (Maximum Contamination Level) or Treatment Technology be established as part of the National Primary Drinking Water Regulations.
Some may argue that removal is equivalent to disinfection. George Clifford White however, defines disinfection as the process of destroying pathogenic microorganisms in water by physical or chemical means. There is little to no mention of disinfection or inactivation of Cryptosporidium in the IESWTR due to the view that measurement and monitoring techniques have not developed adequately to support a rule. The rule does however embrace the idea of giving community water systems a two log (99 percent) removal credit if filtration systems are operated at or below new turbidity standards.
This contrasts to the current SWTR (Surface Water Treatment Rule) for Giardia and viruses where a three log (99.9 percent) and four log (99.99 percent) respectively removal/inactivation level is required. Unfortunately, it won’t be until the development of LT2ESWTR that disinfection/inactivation of Cryptosporidium and the idea of multiple barriers will be addressed. This second rule is required to be promulgated in November 2000. Plans to begin work on this rule are in place for mid December.
Preliminary discussions have embraced the idea of a risk based rule for Cryptosporidium. The goal will be to reduce the risk to 10-4 or 1 illness in 10,000.
In The UK
The Department of the Environment, Transport and the Regions (DETR) in the United Kingdom has approached the subject of Cryptosporidium and the regulation thereof in a much different way. In May 1988, DETR released a consultation paper entitled “Preventing Cryptosporidium Getting into Public Drinking Water Supplies.” UK water utilities were asked to review this document and comment back by June 30th, 1998.
In The UK
The document proposes that there is a case for increased monitoring of Cryptosporidium and that if unacceptable levels (1 oocyst in 10 liters) are found in water supplies the Drinking Water Inspectorate would consider prosecution of the company. There would be a new criminal offense for failing to treat water to adequately remove Cryptosporidium oocysts. On conviction in a Crown Court, the offense would carry the penalty of an unlimited fine.
In The UK
The intention is to establish that water treatment plants are maintained and operated according to best practice. According to a high ranking official in one of the major UK water utilities, this rule or some derivation could be in place as early as December of this year. It could also take a lot longer!
The European Union
The new proposed European Union Drinking Water Directive contains similar provisions. The new directive proposes that water must be “free from any microorganisms and parasites and from any substances which, in numbers or concentrations, constitute a potential danger to human health.” Once adopted, the new Directive will be transposed into UK law. Adoption of this new Directive is expected this year.
Manufacturer’s Viewpoint
Hopefully, science will evolve on the measurement and monitoring front so that existing and proven disinfection technologies can soon be utilized for the purpose of reducing risk of Cryptosporidiosis. There is already a reasonable amount of documentation on the performance of each technology with respect to log inactivation. Sure they vary widely but, in fact, each can make a contribution to lowering the risk of Cryptosporidiosis if used. Some may only provide a fraction of a log inactivation but they exist now! These technologies include advanced ultraviolet light, low grade steam, chlorine dioxide, chlorine, ozone and sequential disinfection; i.e., combinations of chlorine, chloramines and or ozone.
Manufacturer’s Viewpoint
It is interesting to note that the UK has the same access to monitoring techniques as does the US. The broader issue is money and when and how it should be spent. US utilities are optimizing processes first and based on realized performance will be in a better position to know when to invest and on what new capital equipment. The UK on the other hand seems to rely on the utilities to comply with directives, assure public health and add the cost of these improvements into their K factor (rate increase basis) when it comes up for re-negotiation every five years.
Manufacturer’s Viewpoint
Time will tell which is the better way.
