Monitoring Reclaimed Wastewater Usage on Public Parkland Vegetation to Reduce Risks

The following are excerpts from an article in the journal Water and Wastes Digest. The full article is posted at,

. . . There is justifiable concern about residual pathogenic organisms and hazardous or otherwise deleterious chemicals present in many treated domestic wastewater discharges. The use of wastewater reclaimed by treatment approaches that do not truly disinfect for all human pathogenic organisms, residual organics, and other constituents typically present in secondary-treated effluents must be considered carefully.

. . . Reclaimed Domestic Wastewater Treatment Performance Standards

The performance standard that should be achieved in any domestic wastewater reuse project is one of treating the incoming wastestream to a sufficient degree to control waterborne pathogens so that those who use a golf course, park, playground, softball field, botanical garden or any area irrigated with treated and reclaimed effluent experience no increased risk of disease compared to the situation that would exist if the area was irrigated with typically treated public water supplies.

Today, the sanitary quality of domestic water supplies and reclaimed domestic wastewaters is judged by the fecal coliform standard. It has been recognized since the 1940s that this standard will not protect public health from enteroviruses and cyst-forming protozoans (Lee and Jones-Lee 1993). It also has been long known that about one million people become ill and about 1,000 people die every year in the US due to infections caused by these organisms in public water supplies that meet the fecal coliform standard. It was not until the Milwaukee Cryptosporidium outbreak in April of 1993 that sufficient attention has been given to what are inadequate treatment standards to judge the safety of public water supplies. This unfortunate episode, in which 400,000 people became ill and about 100 died, had its origins in a contaminated water supply that met fecal coliform standards.

As a result of this Milwaukee incident, it has now become well known that enteroviruses and Cryptosporidium are commonly present in water treated to meet the fecal coliform standard. Therefore, those who have contact with such water are exposed to part of the endemic pathogen problem that causes large numbers of people to become ill with diarrhea, vomiting, etc. and a few people, especially the very young, the elderly and those with system immune deficiencies, to die . . .

The magnitude of public health problems associated with contact with inadequately treated reclaimed wastewaters that just meet the coliform standard is significantly greater than for those who have the same kind of contact with typical public water supplies that just meet fecal coliform standards. This arises from the fact that domestic wastewaters typically contain far greater concentrations of pathogenic enteroviruses and protozoan cysts than typical domestic water supplies.

. . . it is important to not assume that even treatment of domestic wastewater by the activated sludge or trickling filter processes, followed by secondary clarification with alum or iron/polymer addition, rapid sand filtration, chlorination and dechlorination will produce an end product that can be safely used for irrigation of publicly used areas. Remember, Milwaukee was practicing treatment that exceeded the standards typically associated with these processes when the Cryptosporidium outbreak occurred . . .

. . . Reuse Area Monitoring: For the many types of publicly-used areas already described, where the public will have possible contact residual constituents, it is important to sample the turf, grass and other vegetation and soil for an accumulation of pathogenic organisms, such as protozoan cysts and enteroviruses. This monitoring is essential to evaluate the reliability of the effluent monitoring program, and to determine what the public is actually exposed to through the use of these areas as a result of applying the reclaimed domestic wastewaters. It should not be assumed that just because the effluent monitoring does not detect any problems, that there is not sufficient buildup of potentially hazardous situations that could be a threat to public health and the environment . . .

Informing the Public of Potential Hazards

For those areas that either do not conduct a monitoring program . . . or where such a program shows that the irrigated area contains potentially pathogenic enteroviruses and/or cyst-forming protozoans, the very least that should be done is to post large signs in the area irrigated with domestic reclaimed wastewater. These signs should state, “This area has been irrigated with reclaimed domestic wastewater that has not necessarily been adequately treated to protect public health and the environment. Persons using this area could experience illness, and possibly death due to the residual pathogenic organisms and hazardous chemicals in the reclaimed domestic wastewater used to irrigate the area.”

Additional information and numerous references on this subject can be obtained from the authors.

G. Fred Lee, Ph.D., P.E., D.E.E., and Anne Jones-Lee, Ph.D., are president and vice-president, respectively, of G. Fred Lee and Associates, a specialty environmental consulting firm located in El Macero, California.

Source: Water Engineering & Management   November 1995

Copyright © 2011 Scranton Gillette Communications


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