Planned and unplanned potable water reuse: water quality, health issues, environmental risk and catchment management
(RelianaLumbanToruan-Research Centre for Limnology)
Introduction
Water, without a doubt, is our critical natural resources and there are many supply-demands conflicting on it and, now, the world facing water scarcity due to increasing supply-demands, climate variability and contamination of water bodies. Attribute to importance of water resources, humans have tried to control water usage in variety of ways and, for many decades, worked to find better alternatives for increasing water resource availability. Water reuse and reclamation is one of the solutions where many scientists are working on in order to generate new concept of reliable water supply. Increasing demand, diminishing water supply and deterioration in natural water quality are now become the driving force in building water reused project, not only in relatively water deficient countries but also in highly populated city (Lazarova et al. 2003 and Rodriguez et al. 2009). However, the application of treated wastewater reuse, to date, is still limited to non-potable plan, such as parks watering and gardening, municipal irrigation, agriculture and industrial.
is discharged to a river and incidentally abstracted by downstream community for drinking water supply and generally without awareness that natural water supply has received upstream treated water (Gleick, 2000).
There is still major concern of public and environmental health towards potable reuse despite the fact that wastewater treatment technology are now available to treat wastewater into a very high standard of drinking water. Many evidence showed that these issues have led to the postponement of most potable reuse proposals (Huertas et al. 2008 and Hartley, 2006). It was found that non- potable reuses were likely much more accepted by public and likely more feasible for future alternatives in recycled water reuse. The study of Hurlimann (2007) and Mark et al. (2006), have also found that public are less favourable towards recycled water reuse for potable reuse either direct or indirect. This paper will discuss the issues concerning the water quality, health and environmental risk toward reclaimed water for potable water reuse (planned and unplanned). Moreover, public opinion and awareness as regards to planned and unplanned potable water reuse will also be discussed.
Indirect planned and unplanned potable reuse
Upper Occoquan region in Virginia (USA) (Tchobanoglous et al. 2003). Unplanned potable reuse is also commonly found in developing riparian countries, where community abstract water from a river and directly or indirectly use for drinking water supply. The common planned indirect potable reuse is by infiltration and direct injection of treated water into the aquifer or groundwater system and discharge the recycled water into potable water storage (Drewes et al. 2003). In Singapore, for example, planned indirect potable reuse is generated by implemented secondary water treatment followed by such advanced processes such as membrane filtration, reverse osmosis, UV disinfection, stability control and chlorine disinfection (Law, 2005). (Figure 1) shows the schematic diagram of indirect potable water reuse.
Figure 1.Schematic diagram of indirect water reuse, adopted from (Drewes et al. 2003)
Consequently, the receiving water capacity to naturally purify discharging effluents is also decreasing.
Therefore, even though the wastewater has been treated to a certain criteria before discharged to a natural system, there is a possibility of recontamination and cross contamination to occur in drinking water supply both in planned and unplanned system. In planned potable reuse, for instance, recontamination and changes in water quality may occur during storage and distribution of potable water. In addition, contamination may also occur during aquifer infiltration and recharging processes and in situ contamination. In planned reuse, the common storage for reclaimed water is reservoir, either open or enclosed. Changes in reclaimed water quality and contamination during storage and distribution both in open and enclosed reservoir can occur which mainly associated with physical, biological and chemical qualities. For example, regrowth of pathogenic microorganism is a common occurrence in open and enclosed reservoir due to loss of chlorine residual. In addition, though groundwater is generally assumed of being pathogen free, there has been documented disease associated with groundwater contamination (Asano, 2001). As regard to unplanned potable reuse, the chance for contamination to occur is even higher than that in planned scheme as the treated water being discharged into water body in upstream may be mixed with other treated or untreated effluents, either domestic or industrial effluents.
Contaminants associated with potable reuse
Contaminants in drinking water supply generally originated from three major sources: anthropogenic source, natural source, and contaminants formed during water treatment processes. There are three major contaminants in drinking water supply namely: pathogens, chemicals contaminant and micro pollutant.
Pathogens contaminant
Contamination can also come from septic tank and direct water body contact. The major biological contaminants in water body are divided into four major groups; bacteria, viruses, protozoa, and helminths. The representative pathogenic bacteria in contaminated recycled water are mainly including, Shigella spp., Legionella spp, Mycobacterium spp., Campylobacter, clostridium, Yersinia, and Salmonella spp. (Khan and Roser, 2007 and Wen et al. 2009). Though some of these pathogenic bacteria may also be transmitted through food, water borne transmitted has been reported
Common protozoa encountered in contaminated potable water system are Cryptosporidium parvum, Entamoeba hystolitica, and Giardia intestinalis; helmints such as Ascaris lumbricoides and Trichuris trichiura (Toze, 2006). The problem in potable water supply regarding the occurrence of microbial pollutants has become common especially in unplanned potable water supply as the capacity of the receiving water body to naturally purify discharged waste and wastewater is overwhelmed by increasing waste inflows over time. However, the detection and identification method of biological contaminant in water body is still notoriously expensive and difficult. The common practice is to use the presence of Escherichia coli and other coli forms bacteria in water to indicate the likely presence of other pathogenic bacteria.
Chemicals contaminant
Micro pollutants
Micro pollutants refer to traces of pharmaceutically active compounds (PhAC), fate of personal care products such as estrogenic and androgenic hormones and other unregulated trace pollutants. Significant amount of drugs residual will leave human via urine and faeces after several metabolic reaction, such as hydroxylation, cleavage or glucuronation (Hirsch et al. 1999). Unmetabolized compounds then enter the raw sewage and manure which can contaminate potable water supply. PhACs are recently reported present in groundwater and in municipal wastewater, mainly the fate of analgesics and anti inflammatory drugs such as ketoprofen, dilofenac, and acetaminophen. Frequently identified PhACs in water are coprostanol (faecal steroid), insect repellent (DEET), caffeine (using as stimulant), triclosan (antimicrobial disinfectant commonly used in body soap and face wash cream), and non-ionic detergent metabolite (Watkinson et al. 2009). Recent study found that many of these active pharmaceutical compounds are persistent as they were being release to conventional wastewater treatment and not completely removed during water treatment processes and may pose risk to human and environment (Wang et al. 2005). As an example the study of Radjenovic et al. (2008) noted that excellent nano filtration and reverse osmosis processes were note to reject some pharmaceutical active compounds such as acetaminophen, gemfibrozil and mefenamic.
Health and environmental risk of potable reuse
Giardia and Cryptosporidium are the agents for watery diarrhoea. Human are infected by these pathogen through ingestion of the cysts found in water.
The second concern is the risk of trace of PhACs, personal care and endocrine disrupting compounds (EDCs). Continuous disposal of PhACs, personal care products and EDCs into water body can lead to serious health problem and can affect aquatic life. Some PhACs and EDCs have been recognised to be responsible for the majority natural endocrine disrupting processes in aquatic organism. Furthermore, the study of Fernandez et al. (2008) found that EDCs in environmental have been detected as being responsible to adverse reproductive effects in several fish species exposed to municipal wastewater treatment plant and were potential to cause a similar effect on human reproductive system. The major concern regarding human PhACs in environments is the possibility of microbial assemblages to develop antimicrobial resistance which can have implication to human and public health (Crane et al. 2006). Previous study found that Klebsiellae strains resistant to antibiotic have caused an epidemic disease in hospital and found that Klebsiellaes exhibited resistances against amphicillin. Furthermore, the presence of antibiotic in water body has been found to influence denitrification rates. Constanzo (2005) asserts that depressed in denitrification rate has been identified as respond to the occurrence of amoxicillin, erythromycin, and clarithromycin.
Table1. Typical contaminants found in treated wastewater effluent and their impact
Typical contaminants Effects on human and environmental health
Inorganic and organic colloidal and suspended solid
- Suspended solid
- Colloidal solids
- Organic matter
May cause sludge deposits or interfere with receiving water clarity
May deplete oxygen resources in water catchment
Toxic to human; carcinogenic Toxic to human; carcinogenic Cause endocrine disruption and sex
reversal on aquatic species
Cause foaming and may interfere with coagulation
- Viruses Cause disease Source: (Tchobanoglous et al. 2003)
Potable water catchment management
In order to satisfy potable water supply and to gain public acceptance in regard to potable water reuse, it is important that the water authority be able to ensure the safety of drinking water delivered to consumer. As regard to planned potable reuse, an important issue in the implementation of planned potable reuse is the storage for drinking water supply and its management. There are some problem commonly occur in drinking water catchment as respond to water contamination which lead to deterioration of potable water quality. Any effort to maintain the quality of drinking water source is essential. In planned potable system, open reservoirs are the common water storage used for surface water augmentation while aquifer is used for subsurface augmentation. The principal problems encountered in potable water reservoir are under physical, chemical and biological parameter including: release of odours, temperature stratification, loss of chlorine residual, low dissolved oxygen resulting in odours, excessive growth of algae and phytoplankton, high level of turbidity and colour which is related to aesthetic concerns, and regrowth of microorganism. Effective management of drinking water catchment can be delivered by two options; external and internal management. External management is applied by protection of catchment area from changed land use and sewage treatment plant, therefore contamination from industrial effluent and agricultural runoff to water catchment can be eliminated. Involvement of local people (for instance land owner and farmer) is essential in external management. Australia is one of countries that have a strong regulation toward land use in protected water catchment area.
promotes algae and phytoplankton growth. In addition, annual dredging of accumulative sediment can be implemented to limit the formation of deposit and release of hydrogen sulphide. The second strategy is chemical treatment which can control microorganism and phytoplankton growth in the reservoir. Chlorine can be added to maintain residual chlorine in the water body to avoid regrowth of pathogenic microorganisms. However, the chlorine application should be limited in small amount as chlorine can combine with other odour-causing compounds and release odours with greater intensity.
Conclusion
Indirect potable reuse is being practised at several regions as a feasible option to augment potable water supply and much of the practice is of relevance to planned and unplanned indirect potable reuse. Water quality issues have been the major concerns both in planned and unplanned potable reuse due to possibility of contamination and cross contamination during the storage and distribution recycled water that has been blended with natural drinking water source. Due to more risk aware in potable reuse either planned or unplanned, it is important to ensure the safety of drinking water distributed to consumer. Public will keep aware on recycled water reuse for potable supply either it is planned or unplanned. No matter how many technological advances have been made to deliver high quality recycled water, a number of obstacles are stay behind before planned potable reuse is broadly implemented. People are historically opposed direct potable reuse concept as they believe that recycled water has lower quality than the pristine water from where drinking water is supplied, therefore recycled water is not supposed to be used for potable use and some believes that it is not supposed to be mixed with natural water supply such as groundwater.
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