Potable wter reuse_Reliana_edited reliana_edit 2okt
Planned and unplanned potable water reuse: water quality, health issues, environmental
risk and catchment management
(RelianaLumbanToruan-Research Centre for Limnology)
Reliana@limnologi.lipi.go.id
Introduction
Water, without a doubt, is our critical natural resources and there are many supplydemands conflicting on it and, now, the world facing water scarcity due to increasing 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.
Accordingly, cities experiencing limited water resource are now considering potable
water reuse though it is limited to indirect potable reuse rather than direct reuse. Indirect potable
reuse scheme is now becoming more common and in increasing trends worldwide while direct
potable reuse; when the wastewater is treated to a potable quality and directly piped into drinking
water system, is still limited. The well known existing direct potable reuse plant is in Winhoek,
Namibia. The Windhoek “Goreangab” water reclamation plant is the first direct potable reuse
scheme and still exist to date. In 2002 the plant was able to treat 4.8 ML wastewater per day and
produce reclaimed water which contributed to 4% drinking water supply in the area (du Pisani,
2006). In indirect potable reuse, wastewater is highly treated and discharged directly in to
groundwater and or surface water (rivers, lakes and reservoirs) in intention to augment drinking
water supplies. The focus of indirect potable reuse is in planned scheme, nevertheless, incidental
or unplanned potable reuse can also occur where treated water from wastewater treatment plant
1
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
Indirect potable reuse refers to recycled water that is planned (intentionally) or unplanned
(unintentionally) discharged to a water system (lakes, rivers, reservoirs and aquifers) where then
the water is abstracted form the groundwater and surface water to provide drinking water supply.
It is unplanned because the treated water being discharged to the river, for example, is not intent
to be reused downstream for potable water supply; however, it is, unintentionally, reused for
potable supply. Unplanned potable reuse is a common practice since long time ago when people
commonly abstract water from river and or lakes for their drinking water supply. The Rhine and
River Thames are example for unplanned indirect potable reuse, it is receiving 20-50% of urban
and industrial treated wastewater, and these river are important potable water source for the
region (Rowe and Abdel-Magid, 1995). Another example of unplanned potable reuse is the
Ciliwung and Citarum River in West Java, Indonesia, to which is discharged treated effluents
from towns along the rivers system from where The City of Bandung, Jakarta and surrounding
areas draw part of their supplies. Whereas, the major population centres with established planned
indirect potable reuse schemes for example are in Singapore, Orange County (California) and the
2
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)
The major concern and challenge in planned and unplanned water scheme is the quality
of reclaimed water that, in planned or unplanned, is reused for drinking water supply. In planned
potable reuse scheme, the treated water has been highly treated to meet the desirable criteria and
standard for drinking water before discharging into potable water storage or catchment. The
point of discharging treated water into natural water system considering that natural cycle have a
high capacity to purify the recycled water. Water retention time in the natural system will allow
any remaining contaminant to be degraded naturally. Unfortunately, population pressure and
industrial development have resulted in increasing of wastewater flow to a natural water body.
3
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
Potable water supply may be contaminated by different pathogens excreted by humans and
animals either by diseases or naturally excreted to environment. Improper water and domestic
sewage treatment are the main source of pathogenic microorganisms in recycled water.
4
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
Chemicals may occur in potable water supply from waste and wastewater discharging
from industry, household, humans and animals excreta, nutrient loading from agricultural water
runoff, such as nitrogen and phosphorus, and chemicals formed during wastewater and potable
water treatment processes, such as chlorine. Major chemicals of concern are heavy metal,
pesticide and its metabolites, nutrients (phosphorus and nitrogen), algal toxin which is naturally
produced by common blue green algae such as Microcystis, and disinfection by products such as
trihalomethane (Baggett et al, 2006, Khan and Roser, 2007). Traces of heavy metal contaminants
enter water body through natural processes (rock weathering, erosion and runoff) and
anthropogenic activity such as industrial processes, domestic, leaching from landfills, and
atmospheric pollutants.
5
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
Risks of planned and unplanned potable reuse are mainly associated with the reclaimed
water quality concerning the occurrence of pathogenic microorganisms and chemical
contaminants. The first concern of risks to human health is waterborne disease caused by
pathogenic microorganism which is mainly associated with enteric and non-enteric diseases.
From group of pathogenic bacteria, Salmonella causes diseases ranging from gastroenteritis to
typhoid and paratyphoid fevers, Shigella are the responsible agents of bacillary dysentery and
diarrheal diseases, Legionella pneumophila causes acute pneumonia with relatively high fatality
and affect gastrointestinal track (Bitton, 1994). Endemic and epidemic of cholera and typhoid
transmitted through contaminated drinking has been demonstrated in recent year in some
countries such as Yugoslavia, and South Africa (NHMRC, 2003). Pathogenic protozoa such as
6
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.
Organic chemical such as nutrient residual in reclaimed water and loading from
surrounding area in to potable water storage can promote macrophytes and phytoplankton
growth. In addition to that, excessive algae growth can release odour and give algal taste in
drinking water and some blue green alga can also release toxic substance that harmful for fish
species and human (Tchobanoglous et al. 2003). In term of heavy metals contamination, the main
threats to human health are associated with lead, cadmium, mercury, and arsenic. Effect on
human health is mainly associated with cancer diseases, kidney and lung damage. Typical
contaminant compounds found in treated wastewater effluent and their impact on human and
environmental health are summarised in Table 1.
7
Table1. Typical contaminants found in treated wastewater effluent and their impact
Typical contaminants
Inorganic and organic colloidal and
suspended solid
- Suspended solid
Effects on human and environmental health
- Colloidal solids
- Organic matter
Dissolved organic matter
- Total organic carbon
- Refractory organics
- Volatile organic compounds
- Pharmaceutical active compounds
- surfactan
Dissolved inorganic matter
- Ammonia
- Nitrate
- Phosphorus
- Calcium and magnesium
- Chloride
Biological pathogens
- Bacteria
- Protozoa
May cause sludge deposits or interfere
with receiving water clarity
Can impact disinfection processes by
shielding organisms
May effect effluent turbidity
May shield bacteria during disinfection
and may deplete dissolved oxygen
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
Increase chlorine demand
Can be converted to nitrates, and, in the
process, can deplete dissolved oxygen
With Phosphorus, can lead algal bloom
Toxic to fish
Stimulate alga bloom
Can cause methemoglobinemia in
infants (blue babies)
Stimulate alga bloom
Interfere with coagulation
Increase hardness and TSS
Imparts salty taste
Cause disease associated with gastro
enteritis
Cause disease associated with gastro
enteritis
8
- Viruses
Source: (Tchobanoglous et al. 2003)
Cause disease
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.
Furthermore, in order to maintain the quality of potable water source, internal
management in water storage is also needed. Internal management means that the water quality
is maintained through several treatments including physical, chemical, and biological treatment.
There are some strategies in internal management of water bodies. First, physical treatment by
using variety of aeration system to provide oxygen and eliminate stratification in water body,
hence the release of odours due to lack of oxygen can be eliminated. However, water mixing may
result in release of phosphorus from bottom sediment which then, under some circumstances,
9
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.
References
Asano, T. 2001. Water from waste-water: the dependable water resource. pp. 1-13. Department of
Civil and Environmental Engineering, University of California at Davis, Davis, CA
95616-2311, U.S.A., Stockholm, Sweden.
Baggett, S., Jeffrey, P. and Jefferson, B. 2006. Risk perception in participatory planning for water
reuse. Desalination,187:149-158.
Bitton, G. 1994. Wastewater microbiology, John Wiley and Sons, INC, New York.
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Costanzo, S.D., Murby, J. and Bates, J. 2005. Ecosystem response to antibiotics entering the
aquatic environment. Marine Pollution Bulletin, 51:218-223.
Crane, M., Watts, C. and Boucard, T. 2006. Chronic aquatic environmental risks from exposure
to human pharmaceuticals Science of The Total Environment,367:23-41.
Drewes, J.E., Reinhard, M. and Fox, P. 2003. Comparing microfiltration-reverse osmosis and
soil-aquifer treatment for indirect potable reuse of water. Water Research,37:3612-3621.
Du Pisani, P.L. 2006. Direct reclamation of potable water at Windhoek's Goreangab reclamation
plant. Desalination,188:79-88.
Fernandez, M.P., Buchanan, I.B. and Ikonomou, M.G. 2008. Seasonal variability of the reduction
of in estrogenic activity at municipal WWTP. Water Research, 42:3075-3081.
Gleick, P.H. 2000. The World's Water 2000-2001: The Biennial Report on Freshwater Resources,
Island Press, Washington D.C.
Hartley, T.W. 2006. Public perception and participation in water reuse. Desalination,187:115126.
Hirsch, R., Ternes, T., Haberer, K. and Kratz, K.L. 1999. Occurrence of antibiotics in the aquatic
environment. The Science of The Total Environment, 225:109-118.
Huertas, E., Salgot, M., Hollender, J., Weber, S., Dott, W., Khan, S., Schäfer, A., Messalem, R.,
Bis, B., Aharoni, A. & Chikurel, H. 2008. Key objectives for water reuse concepts.
Desalination, 218:120-131.
Hurlimann, A.C. 2007. Is recycled water use risky? An Urban Australian community's
perspective. Environmentalist, 27:83-94.
Khan, S. and Roser, D. 2007. Risk assessment and health effects studies of indirect potable reuse
schemes. pp. 1-45. Centre for Water and Waste Technology, University of New South
Wales, New South Wales.
Law, I.B. 2005. Potable reuse - What are we afraid of? , Vol. 2 May.
Lazarova, V., Hills, S. & Birks, R. 2003. Using recycled water for non-potable, urban uses: a
review with particular reference to toilet flushing. Water Science and Technology: Water
Supply, 3:69-77.
Mark, J.S., Martin, B. & Zadoroznyj, M. 2006. Acceptance of water recycling in Australia:
National baseline data. Water Journal of the Australian Water Association.
NHMRC .2003. AUSTRALIAN DRINKING WATER GUIDELINES 6. National Water Quality
Management Strategy. NHMRC.
Radjenovic, J., Petrovic, M., Ventura, F. & Barcelo, D. 2008. Rejection of pharmaceuticals in
nanofiltration and reverse osmosis membrane drinking water treatment. Water Research,
42:3601-3610.
Rodriguez, C., Buynder, P.V., Lugg, R., Blair, P., Devine, B., Cook, A. & Weinstein, P. 2009.
Indirect potable reuse: A sustainable water supply alternative. Int. J. Environ. Res. Public
Health, 6:1174-1209.
Rowe, D.R. & Abdel-Magid, I.M. 1995. Wastewater Reclamation and Reuse, Lewis Publisher.
11
Tchobanoglous, G., Burton, F.L. & Stensel, H.D. 2003. Wastewater engineering: treatment and
reuse / Metcalf & Eddy, Inc., McGraw-Hill, Boston; Sydney.
Toze, S. 2006. Water reuse and health risks -- real vs. perceived. Desalination,187:41-51.
Wang, Y., Hu, W., Cao, Z. & Fu, X. 2005. Occurrence of endocrine-disrupting compounds in
reclaimed water from Tianjin, China. Analytical Bioanalytical Chemistry, 383:857-863.
Watkinson, A.J., Murby, E.J., Kolpin, D.W. & Costanzo, S.D. 2009. The occurrence of
antibiotics in an urban watershed: From wastewater to drinking water. Science of The
Total Environment, 407:2711-2723.
Wen, Q., Tutuka, C., Keegan, A. & Jin, B. 2009. Fate of pathogenic microorganism and
indicators in secondary activated sludge wastewater treatment plants. Journal of
Environmental Management, 90:1442-1447.
12
risk and catchment management
(RelianaLumbanToruan-Research Centre for Limnology)
Reliana@limnologi.lipi.go.id
Introduction
Water, without a doubt, is our critical natural resources and there are many supplydemands conflicting on it and, now, the world facing water scarcity due to increasing 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.
Accordingly, cities experiencing limited water resource are now considering potable
water reuse though it is limited to indirect potable reuse rather than direct reuse. Indirect potable
reuse scheme is now becoming more common and in increasing trends worldwide while direct
potable reuse; when the wastewater is treated to a potable quality and directly piped into drinking
water system, is still limited. The well known existing direct potable reuse plant is in Winhoek,
Namibia. The Windhoek “Goreangab” water reclamation plant is the first direct potable reuse
scheme and still exist to date. In 2002 the plant was able to treat 4.8 ML wastewater per day and
produce reclaimed water which contributed to 4% drinking water supply in the area (du Pisani,
2006). In indirect potable reuse, wastewater is highly treated and discharged directly in to
groundwater and or surface water (rivers, lakes and reservoirs) in intention to augment drinking
water supplies. The focus of indirect potable reuse is in planned scheme, nevertheless, incidental
or unplanned potable reuse can also occur where treated water from wastewater treatment plant
1
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
Indirect potable reuse refers to recycled water that is planned (intentionally) or unplanned
(unintentionally) discharged to a water system (lakes, rivers, reservoirs and aquifers) where then
the water is abstracted form the groundwater and surface water to provide drinking water supply.
It is unplanned because the treated water being discharged to the river, for example, is not intent
to be reused downstream for potable water supply; however, it is, unintentionally, reused for
potable supply. Unplanned potable reuse is a common practice since long time ago when people
commonly abstract water from river and or lakes for their drinking water supply. The Rhine and
River Thames are example for unplanned indirect potable reuse, it is receiving 20-50% of urban
and industrial treated wastewater, and these river are important potable water source for the
region (Rowe and Abdel-Magid, 1995). Another example of unplanned potable reuse is the
Ciliwung and Citarum River in West Java, Indonesia, to which is discharged treated effluents
from towns along the rivers system from where The City of Bandung, Jakarta and surrounding
areas draw part of their supplies. Whereas, the major population centres with established planned
indirect potable reuse schemes for example are in Singapore, Orange County (California) and the
2
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)
The major concern and challenge in planned and unplanned water scheme is the quality
of reclaimed water that, in planned or unplanned, is reused for drinking water supply. In planned
potable reuse scheme, the treated water has been highly treated to meet the desirable criteria and
standard for drinking water before discharging into potable water storage or catchment. The
point of discharging treated water into natural water system considering that natural cycle have a
high capacity to purify the recycled water. Water retention time in the natural system will allow
any remaining contaminant to be degraded naturally. Unfortunately, population pressure and
industrial development have resulted in increasing of wastewater flow to a natural water body.
3
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
Potable water supply may be contaminated by different pathogens excreted by humans and
animals either by diseases or naturally excreted to environment. Improper water and domestic
sewage treatment are the main source of pathogenic microorganisms in recycled water.
4
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
Chemicals may occur in potable water supply from waste and wastewater discharging
from industry, household, humans and animals excreta, nutrient loading from agricultural water
runoff, such as nitrogen and phosphorus, and chemicals formed during wastewater and potable
water treatment processes, such as chlorine. Major chemicals of concern are heavy metal,
pesticide and its metabolites, nutrients (phosphorus and nitrogen), algal toxin which is naturally
produced by common blue green algae such as Microcystis, and disinfection by products such as
trihalomethane (Baggett et al, 2006, Khan and Roser, 2007). Traces of heavy metal contaminants
enter water body through natural processes (rock weathering, erosion and runoff) and
anthropogenic activity such as industrial processes, domestic, leaching from landfills, and
atmospheric pollutants.
5
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
Risks of planned and unplanned potable reuse are mainly associated with the reclaimed
water quality concerning the occurrence of pathogenic microorganisms and chemical
contaminants. The first concern of risks to human health is waterborne disease caused by
pathogenic microorganism which is mainly associated with enteric and non-enteric diseases.
From group of pathogenic bacteria, Salmonella causes diseases ranging from gastroenteritis to
typhoid and paratyphoid fevers, Shigella are the responsible agents of bacillary dysentery and
diarrheal diseases, Legionella pneumophila causes acute pneumonia with relatively high fatality
and affect gastrointestinal track (Bitton, 1994). Endemic and epidemic of cholera and typhoid
transmitted through contaminated drinking has been demonstrated in recent year in some
countries such as Yugoslavia, and South Africa (NHMRC, 2003). Pathogenic protozoa such as
6
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.
Organic chemical such as nutrient residual in reclaimed water and loading from
surrounding area in to potable water storage can promote macrophytes and phytoplankton
growth. In addition to that, excessive algae growth can release odour and give algal taste in
drinking water and some blue green alga can also release toxic substance that harmful for fish
species and human (Tchobanoglous et al. 2003). In term of heavy metals contamination, the main
threats to human health are associated with lead, cadmium, mercury, and arsenic. Effect on
human health is mainly associated with cancer diseases, kidney and lung damage. Typical
contaminant compounds found in treated wastewater effluent and their impact on human and
environmental health are summarised in Table 1.
7
Table1. Typical contaminants found in treated wastewater effluent and their impact
Typical contaminants
Inorganic and organic colloidal and
suspended solid
- Suspended solid
Effects on human and environmental health
- Colloidal solids
- Organic matter
Dissolved organic matter
- Total organic carbon
- Refractory organics
- Volatile organic compounds
- Pharmaceutical active compounds
- surfactan
Dissolved inorganic matter
- Ammonia
- Nitrate
- Phosphorus
- Calcium and magnesium
- Chloride
Biological pathogens
- Bacteria
- Protozoa
May cause sludge deposits or interfere
with receiving water clarity
Can impact disinfection processes by
shielding organisms
May effect effluent turbidity
May shield bacteria during disinfection
and may deplete dissolved oxygen
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
Increase chlorine demand
Can be converted to nitrates, and, in the
process, can deplete dissolved oxygen
With Phosphorus, can lead algal bloom
Toxic to fish
Stimulate alga bloom
Can cause methemoglobinemia in
infants (blue babies)
Stimulate alga bloom
Interfere with coagulation
Increase hardness and TSS
Imparts salty taste
Cause disease associated with gastro
enteritis
Cause disease associated with gastro
enteritis
8
- Viruses
Source: (Tchobanoglous et al. 2003)
Cause disease
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.
Furthermore, in order to maintain the quality of potable water source, internal
management in water storage is also needed. Internal management means that the water quality
is maintained through several treatments including physical, chemical, and biological treatment.
There are some strategies in internal management of water bodies. First, physical treatment by
using variety of aeration system to provide oxygen and eliminate stratification in water body,
hence the release of odours due to lack of oxygen can be eliminated. However, water mixing may
result in release of phosphorus from bottom sediment which then, under some circumstances,
9
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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