“Water Recycling Research Project Example About 5 million people die each year from poor drinking water, poor sanitation, or a dirty home environment – often resulting from water shortage” (University of Wisconsin-Madison 2001). While water continues to be a precious commodity in some parts of the world, people tend to waste water in other parts, without realizing the implications these may have. In a report in BBC News Geneva in the year 2006, water shortage is caused by a combination of climate change and mismanagement of resources. Reports by World Wildlife Fund (WWF) reveal that water used in some of the richest cities in the world exceeds the water supply and some wealthy countries also diminish the supply in developing countries (Foulkes 2006).
It is such a shame that water, a basic need, has become a scarcity in several countries all over the world. In other countries where water supply is not scarce, the poor quality of water is what plagues them. The problems of climate change but add another unknown effect in the progress of this water crisis. Another threat to the limited water supply that the world has is the growing population, increasing the demand for water.
Aware of this crisis, several steps have already been taken to try to alleviate this problem, and to perhaps provide a permanent solution to exceeding demand vs. available water supply. In a publication released by the American Society of Mechanical Engineers, they presented four technologies that can possibly help different countries in the world in dealing with the present, and the impending water crisis. These are desalination, aquifer storage and recovery, water recycling and reuse, and improved irrigation technology including remote sensing and hydrodynamic gates (American Society of Mechanical Engineers 2003).
Water Recycling: Uses and Process
One technology, water recycling and reuse, is one of the most hopeful methods of maximizing water use. WateReuse Association is a nonprofit organization whose purpose is to improve benefits and efficiency of water supply through education, sound science, and technology to benefit the environment and the public through the use of reclamation, recycling and reuse, and desalination. Water recycling is defined as “the reuse of treated wastewater for beneficial purposes such as agricultural and landscaping irrigation, industrial processes, toilet flushing, or replenishing a groundwater basin” (WateReuse Association n.d.). In other words, it is using wastewater for a number of times in different useful applications. Reusing water enables different communities to decrease reliance on ground and surface water sources. It also reduces pollution, may be used to refill overused water sources and to restore those sources destroyed or damaged in the past.
Typically, there are several ways in which recycled water can be used. It can be used for surface, landscape, golf course, and food crop irrigation, toilet flushing, industrial processes, washing of vehicles, and potable reuse, among others.
In treating wastewater for reuse, the quality of water is ensured by utilizing several treatment stages which changes depending on where and how the water will be used. There are four main stages, namely Primary Treatment, Secondary Treatment, Tertiary Treatment, and Disinfection (WateReuse Association n.d.).
The typical treatment of wastewater makes use of a combination of chemical, physical, and biological procedures to remove solids, organic matter, and even nutrients from the water. The Food and Agriculture Organization (FAO) of the United Nations, describes the different levels of general wastewater treatment. These are Preliminary Treatment, Primary Treatment, Secondary Treatment, and the last level, which is the Tertiary or Advanced Wastewater Treatment. 1Figure 1, reproduced below, shows a flow diagram of the different levels of wastewater treatment by Asano et al (FAO 1992).
Figure 1
[1]
In the preliminary stage of water treatment, coarse solids and other large particles in wastewater are removed through coarse screening, grit removal, and comminution. During the primary treatment of wastewater, organic and inorganic solids that tend to settle are removed by sedimentation while materials that tend to float are removed by skimming. In several industrialized countries, this level of treatment is the minimum requirement for wastewater irrigation of crops that are not consumed by humans, orchards, vineyards, and food crops that are processed. Secondary treatment follows the primary treatment, wherein primary effluent undergoes further removal of biodegradeable dissolved and colloidal organic substance through the utilization of aerobic biological treatment processes. This is done through the use of oxygen with aerobic microorganisms that metabolize organic materials in wastewater. High rate processes use high concentrations of microorganisms. These processes include sludge process, biofilters, oxidation ditches, and rotating biological contactors. In treating wastewater with high concentration of organic material, a combination of the different processes may be used in series.
The advanced or tertiary treatment is used when there are still substances that cannot and were not removed during the secondary treatment. During treatment, removal of nitrogen, phosphorus, suspended solids, refractory organics, heavy metals, and dissolved solids happen. 2The Bardenpho process, as shown in Figure 2 below, is a method to remove such constituents in wastewater. There are five zones where effluent passes through to the biological reactor. These are: 1) anaerobic fermentation zone (very low dissolved oxygen levels plus absence of nitrates), 2) anoxic zone (low dissolved oxygen levels with the presence of nitrates, 3) aerobic zone (ventilated), 4) secondary anoxic zone, and 5) final aeration zone (FAO 1992).
Figure 2
An additional treatment process in reusing wastewater is called disinfection. This process usually entails introducing a chlorine solution at the head part of a chlorine contact basin. The amount of chlorine depends on several factors, including the strength of the wastewater. Quantities of 5 to 15 mg with a contact time of 30 minutes are common but in cases of wastewater treatment requirements and on the application of recycled wastewater, chlorine contact time can run for as long as 120 minutes or 2 hours.
After treatment of wastewater, a proper storage facility is needed to ensure several things. This includes equalization in daily changes in water flow from treatment plant, storage of excess in cases of too much wastewater as compared to irrigation demands, to meet maximum irrigation demands, to curtail effects of interruption in treatment plant operations and irrigation system, to prevent the possibility of low-quality recycled wastewater from entering the irrigation system, and to buy additional time to settle transient problems regarding water quality.
[2]
Systems used in reclaiming wastewater should be able to provide reliable and consistent treatment by meeting the design and operational requirements such as alarm systems, standby power source, emergency storage or disposal of poorly treated wastewater, monitoring mechanisms, and automatic controllers. Effective and steadfast disinfection is also important in wastewater treatment (FAO 1992).
Brief History of Water Recycling/Reclaiming
1The first small urban reuse system started in the year 1912, with the irrigation of the Golden Gate Park in San Francisco. 2Israel started reusing wastewater for crop irrigation in the year 1965. 3A year after Florida constructed its Tallahassee Reclaimed Water Farm. 4In 1977, the City of St. Petersburg built the first large urban reuse system in the United States. 5The use of reclaimed wastewater from Ochiai Wastewater Treatment Plant for toilet flushing was utilized in Tokyo in the year 1984 in commercial buildings within the district of Shinjuku. 6A year later, Water Consery II, the largest reuse project combining agricultural irrigation and aquifer recharge through rapid infiltration basins, began its operation in Orlando, Florida. 7In 1989, Spain began its irrigation of golf courses using recycled water from Consorci de la Costa Brava wastewater
[3]
treatment facility. 8Irrigation of vegetables like lettuce, cauliflower, broccoli, artichokes, celery, and fennel started in Monterey County, California, in the year 1998. 9In Australia, its largest water reclamation project Virginia Pipeline Project began operations in 1999, using water from Bolivar Wastewater Treatment Plant to irrigate vegetable crops. 10As of 2005, Florida has been using reclaimed water with no reported illnesses, based on a report from the Florida Department of Environmental Protection’s “Water Reuse: Regulatory and Safety Perspectives”.
Water Reuse in the United States
The United States Environmental Protection Agency (EPA) controls the standards of various aspects of wastewater treatment and the quality of drinking water. Majority of states in the US already have set guidelines and criteria for the use of recycled water. In 2004, EPA formed a document containing a summary of state requirements as well as rules for the treatment and use of recycled water called “Guidelines for Water Reuse”. This ensures the safety of projects concerning water reuse in the United States.
Recycled water is mainly used for irrigations of agriculture, landscape, public parks, and golf courses. Other uses include cooling water for power plants and oil refineries, process water to be used in industrial facilities like paper mills and carpet dyers, toilet flushing, dust control, construction activities, concrete mixing, and artificial lakes.
Non-potable applications are more common in the use of recycled water. However, reclaimed water may be also used indirectly for potable function. This includes ground water aquifer recharging and surface water reservoir augmentation. Since 1976, Water Factory 21 Direct Injection Project in Orange County, California has been instilling highly treated recycled water into underground layers that yield water to prevent interference from salt water and at the same time, increases the potable ground water supply (EPA 2009).
Several projects have long been in operation involving water injection. Aside from Water Factory 21, there is also Montebello Forebay Project in California, and similar projects in Arizona, Texas, New York, Florida, and Israel (Commission on Geosciences, Environment and Resources 1994). While success has been proven in ground recharge projects, expansion of surface water reservoirs has been left behind. Nevertheless, several projects have already been launched and a few are still in the planning stages. Since the year 1978, Occoquan Sewage Authority has been providing a potable water supply source for Fairfax County in Virginia, by releasing reclaimed water into a stream above Occoquan Reservoir. A Water Repurification Project is currently being planned in California to expand and increase a drinking water reservoir with 20,000 acre-feet of advanced treated recycled water per year (EPA 2009).
As mentioned earlier, there are several uses and applications of recycled water, depending on the treatment it has undergone. 3Figure 3, reproduced below, illustrates the different areas where recycled water can be used based on the level of treatment.
Water recycling certainly has multiple benefits. First, water recycling ensures that adequate water flow is available to plants wildlife and fish, by meeting water demands, preventing humans from resorting to using water meant for the environment. Second, water recycling significantly decreases harmful discharges to bodies of water that threaten nature. Third, recycling water can aid in establishing and improving wetlands and stream habitats that serve as a habitat for wildlife and wildfowl, flood reduction, fisheries raising ground, and water quality improvement. Another benefit of water recycling is reduction and prevention of pollution. When used in agricultural and landscape irrigation, recycled water [4]may provide more nutrients, decreasing the need to use artificially-made fertilizers (EPA 2009)
Figure 3
Water Recycling in Asia
Just this year, on the month of June, the largest and most advanced water recycling plant in South East Asia called Changi Water Reclamation Plant (CWRP) was opened in Singapore. It is a plant that is able to treat 800,000 cu meters or 320 Olympic-size pools of used water in a day. In Singapore, there are independent systems used in collecting rainwater and for used water. According to Mr. Wah Yuen Long, director for Water Reclamation Plants of PUB, as cited by Business Desk, they have been able to utilize rainwater harvesting on a large scale to cater to the country’s water supply requirements. With the opening of the Changi Water Reclamation Plant, they have been also able to collect and treat used water on a large-scale level as well.
CWRP is cost-effective and compact, using up only 32 hectares which is only a third of the size of a standard plant. With its gravity-driven system, the risk of overflow of used water and pollution is eradicated. The plant’s main elements include a deep pumping station, a sludge dryer, and a covered plant with odor control. The technology used makes sure that the different processes employed can be sustained environmentally. This reduces the amount of plant-induced waste and decreases the strain on landfills. Aside from this water management system, Singapore also has NEWater. NEWater is used water that has undergone treatment using advanced dual membrane technology using microfiltration and reverse osmosis, as well as ultraviolet technology. It could be mixed with water from reservoirs and then go through traditional water treatments to make drinking water (Public Utilities Board Singapore n.d.).
NEWater, when treated at CWRP, will help in its large-scale production and ensure that it will give a sustained supply for future generations. The largest NEWater plant in Singapore is set to be delivered by 2010, ensuring that 30% of Singapore’s water needs are met. It makes sure that every drop of water is recovered through recycling in Singapore, and it is non-dependent on weather changes (Business Desk 2009).
In China, problems with water supply can be attributed to the ever-growing population in the country, increasing the demand on water, while continuously depleting its sources. In the past, water and wastewater treatment in China was a commonwealth, with only limited fees charged for resources and services. This led to large volumes of water being wasted and misused. In 2002, the government revised its Water Resource Law, releasing related regulations and policies like raising water charge and wastewater treatment price.
In general, China has the fourth largest source for water in the world. But because of its large population and problems with water pollution, water supply shortages occur. The earliest water reclamation in China was in the 1950’s, where wastewater was used for irrigation. In 1985, developments on large-scale water reclamation began, from commercial buildings to municipal and industrial sectors. Reused water can be made use of in toilet flushing, lawn irrigation, and car washing. As of 2005, all cities in China were required to have their own wastewater treatment facilities (U.S. Department of Commerce International Trade Administration 2005).
In Japan, the first planned wastewater reclamation started in 1951, as an experiment for supplying industrial water to a paper mill in Tokyo. Serious efforts at water reclamation, however, started in 1964 at the time of severe droughts in several regions of Japan. In the year 1997, 192 areas were provided with reclaimed water coming from 163 public wastewater treatment plants. For toilet flushing in commercial buildings and apartments and water for landscaping, there are 1,475 on-site building reclamation and reuse systems. Water reuse in Japan is primarily used for non-potable urban water purposes. Reclaimed water has been endorsed as a secure, reliable, and esthetically accepted modern water resource for flushing toilets, in-stream flow needs, as well as restoration of the environment.
Because of rapid urbanization in Japan, many small streams have been deserted and aquatic environments were destroyed. During the previous years, the Ministry of Construction and several municipalities have endorsed the use of reclaimed water in repairing damages to the environment (Ogoshi et al. 2001).
Water Quality Standards
To ensure safety of reclaimed water and that it is of good quality, the United States of America has taken several measures throughout the years. 1In 1980, the US Environmental Protection Agency issued the Guidelines for Water Reuse, which was updated in 1992, and 2004). 2In 1988, the Specialist Group on Wastewater Reclamation, Recycling, and Reuse was inaugurated during the 14th Biennial Conference of the International Association on Water Pollution Research and Control, now known as the International Water Association with headquarters in London, United Kingdom. 3A year after, in 1989 Florida implemented a broad
[5]
set of reclaimed water use rules. 4The Florida Legislature instituted formal state objectives in sections 403.064(1) and 373.250 in their Florida Statues, stating “the encouragement and promotion of water conservation and reuse of claimed water”. 5 In 1992, California adopted its own Title 22 reclaimed water rules. 6Year 2001, Florida Department of Agriculture and Consumer Services, Department of Health, Department of Environmental Protection, United States Environmental Protection Agency, Public Service Commission, along with the five water management districts signed the Florida Reclaimed Water Statement of Support (Southwest Florida Water Management District n.d.). The U.S. Environmental Protection Agency has set out the maximum contaminant level goal (MCLG) and maximum contaminant level (MCL) in drinking water as well as the maximum residual disinfectant level goal (MRDLG) and maximum residual disinfectant level (MRDL). Maximum contaminant level goal refers to the level of contaminant in drinking water where no expected or known dangers and threats to health are assumed. On the other hand, maximum contaminant level refers to the highest level of pollutant allowed in drinking water. MRDLG refers to the level of drinking disinfectant where no expected or known dangers and threats to health are assumed while MRDL is the highest level of disinfectant permissible in water for drinking. TT or treatment technique is a required process to reduce contaminant level in water. 1A detailed list of the MCLG, MCL, MRDLG, and MRDL of different water contaminants as well as possible effects from exposure or water intake and the cause of the different pollutants is shown in Table 1 (U.S. Environmental Protection Agency n.d.).
Table 1
| Contaminant | MCLG (mg/L) | MCL or TT (mg/L) | Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term) | Sources of Contaminant in Drinking Water |
| Cryptosporidium | zero | TT | Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) | Human and animal fecal waste |
| Giardia lamblia | zero | TT | Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) | Human and animal fecal waste |
| Heterotrophic plate count | n/a | TT | HPC has no health effects; it is an analytic method used to measure the variety of bacteria that are common in water. The lower the concentration of bacteria in drinking water, the better maintained the water system is. | HPC measures a range of bacteria that are naturally present in the environment |
| Legionella | zero | TT | Legionnaire’s Disease, a type of pneumonia | Found naturally in water; multiplies in heating systems |
| Total Coliforms (including fecal coliform and E. Coli) | zero | 5.0% | Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present | Coliforms are naturally present in the environment; as well as feces; fecal coliforms and E. coli only come from human and animal fecal waste. |
| Turbidity | n/a | TT | Turbidity is a measure of the cloudiness of water. It is used to indicate water quality and filtration effectiveness (e.g., whether disease-causing organisms are present). Higher turbidity levels are often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria. These organisms can cause symptoms such as nausea, cramps, diarrhea, and associated headaches. | Soil runoff |
| Viruses (enteric) | zero | TT | Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) | Human and animal fecal waste |
Disinfection Byproducts
| Contaminant | MCLG (mg/L) | MCL or TT (mg/L) | Potential Health Effects from Ingestion of Water | Sources of Contaminant in Drinking Water |
| Bromate | zero | 0.010 | Increased risk of cancer | Byproduct of drinking water disinfection |
| Chlorite | 0.8 | 1.0 | Anemia; infants & young children: nervous system effects | Byproduct of drinking water disinfection |
| Haloacetic acids (HAA5) | n/a | 0.060 | Increased risk of cancer | Byproduct of drinking water disinfection |
| Total Trihalomethanes (TTHMs) | –> n/a | –> 0.080 | Liver, kidney or central nervous system problems; increased risk of cancer | Byproduct of drinking water disinfection |
Disinfectants
| Contaminant | MRDLG (mg/L) | MRDL (mg/L) | Potential Health Effects from Ingestion of Water | Sources of Contaminant in Drinking Water |
| Chloramines (as Cl2) | MRDLG=4 | MRDL=4.0 | Eye/nose irritation; stomach discomfort, anemia | Water additive used to control microbes |
| Chlorine (as Cl2) | MRDLG=4 | MRDL=4.0 | Eye/nose irritation; stomach discomfort | Water additive used to control microbes |
| Chlorine dioxide (as ClO2) | MRDLG=0.8 | MRDL=0.8 | Anemia; infants & young children: nervous system effects | Water additive used to control microbes |
Inorganic Chemicals
| Contaminant | MCLG (mg/L) | MCL or TT (mg/L) | Potential Health Effects from Ingestion of Water | Sources of Contaminant in Drinking Water |
| Antimony | 0.006 | 0.006 | Increase in blood cholesterol; decrease in blood sugar | Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder |
| Arsenic | 07 | 0.010 as of 01/23/06 | Skin damage or problems with circulatory systems, and may have increased risk of getting cancer | Erosion of natural deposits; runoff from orchards, runoff from glass & electronics production wastes |
| Asbestos (fiber >10 micrometers) | 7 million fibers per liter | 7 MFL | Increased risk of developing benign intestinal polyps | Decay of asbestos cement in water mains; erosion of natural deposits |
| Barium | 2 | 2 | Increase in blood pressure | Discharge of drilling wastes; discharge from metal refineries; erosion of natural deposits |
| Beryllium | 0.004 | 0.004 | Intestinal lesions | Discharge from metal refineries and coal-burning factories; discharge from electrical, aerospace, and defense industries |
| Cadmium | 0.005 | 0.005 | Kidney damage | Corrosion of galvanized pipes; erosion of natural deposits; discharge from metal refineries; runoff from waste batteries and paints |
| Chromium (total) | 0.1 | 0.1 | Allergic dermatitis | Discharge from steel and pulp mills; erosion of natural deposits |
| Copper | 1.3 | TT Action Level=1.3 | Short term exposure: Gastrointestinal distress Long term exposure: Liver or kidney damage People with Wilson’s Disease should consult their personal doctor if the amount of copper in their water exceeds the action level | Corrosion of household plumbing systems; erosion of natural deposits |
| Cyanide (as free cyanide) | 0.2 | 0.2 | Nerve damage or thyroid problems | Discharge from steel/metal factories; discharge from plastic and fertilizer factories |
| Fluoride | 4.0 | 4.0 | Bone disease (pain and tenderness of the bones); Children may get mottled teeth | Water additive which promotes strong teeth; erosion of natural deposits; discharge from fertilizer and aluminum factories |
| Lead | zero | TT; Action Level=0.015 | Infants and children: Delays in physical or mental development; children could show slight deficits in attention span and learning abilities Adults: Kidney problems; high blood pressure | Corrosion of household plumbing systems; erosion of natural deposits |
| Mercury (inorganic) | 0.002 | 0.002 | Kidney damage | Erosion of natural deposits; discharge from refineries and factories; runoff from landfills and croplands |
|
Nitrate (measured as Nitrogen) |
10 |
10 |
Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome. |
Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits |
| Nitrite (measured as Nitrogen) | 1 | 1 | Infants below the age of six months who drink water containing nitrite in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome. | Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits |
| Selenium | 0.05 | 0.05 | Hair or fingernail loss; numbness in fingers or toes; circulatory problems | Discharge from petroleum refineries; erosion of natural deposits; discharge from mines |
| Thallium | 0.0005 | 0.002 | Hair loss; changes in blood; kidney, intestine, or liver problems | Leaching from ore-processing sites; discharge from electronics, glass, and drug factories |
Organic Chemicals
| Contaminant | MCLG (mg/L) | MCL or TT (mg/L) | Potential Health Effects from Ingestion of Water | Sources of Contaminant in Drinking Water |
| Acrylamide | zero | TT | Nervous system or blood problems; increased risk of cancer | Added to water during sewage/wastewater treatment |
| Alachlor | zero | 0.002 | Eye, liver, kidney or spleen problems; anemia; increased risk of cancer | Runoff from herbicide used on row crops |
| Atrazine | 0.003 | 0.003 | Cardiovascular system or reproductive problems | Runoff from herbicide used on row crops |
| Benzene | zero | 0.005 | Anemia; decrease in blood platelets; increased risk of cancer | Discharge from factories; leaching from gas storage tanks and landfills |
| Benzo(a)pyrene (PAHs) | zero | 0.0002 | Reproductive difficulties; increased risk of cancer | Leaching from linings of water storage tanks and distribution lines |
| Carbofuran | 0.04 | 0.04 | Problems with blood, nervous system, or reproductive system | Leaching of soil fumigant used on rice and alfalfa |
| Carbon tetrachloride | zero | 0.005 | Liver problems; increased risk of cancer | Discharge from chemical plants and other industrial activities |
| Chlordane | zero | 0.002 | Liver or nervous system problems; increased risk of cancer | Residue of banned termiticide |
| Chlorobenzene | 0.1 | 0.1 | Liver or kidney problems | Discharge from chemical and agricultural chemical factories |
| 2,4-D | 0.07 | 0.07 | Kidney, liver, or adrenal gland problems | Runoff from herbicide used on row crops |
| Dalapon | 0.2 | 0.2 | Minor kidney changes | Runoff from herbicide used on rights of way |
| 1,2-Dibromo-3-chloropropane (DBCP) | zero | 0.0002 | Reproductive difficulties; increased risk of cancer | Runoff/leaching from soil fumigant used on soybeans, cotton, pineapples, and orchards |
| o-Dichlorobenzene | 0.6 | 0.6 | Liver, kidney, or circulatory system problems | Discharge from industrial chemical factories |
| p-Dichlorobenzene | 0.075 | 0.075 | Anemia; liver, kidney or spleen damage; changes in blood | Discharge from industrial chemical factories |
| 1,2-Dichloroethane | zero | 0.005 | Increased risk of cancer | Discharge from industrial chemical factories |
| 1,1-Dichloroethylene | 0.007 | 0.007 | Liver problems | Discharge from industrial chemical factories |
| cis-1,2-Dichloroethylene | 0.07 | 0.07 | Liver problems | Discharge from industrial chemical factories |
| trans-1,2-Dichloroethylene | 0.1 | 0.1 | Liver problems | Discharge from industrial chemical factories |
| Dichloromethane | zero | 0.005 | Liver problems; increased risk of cancer | Discharge from drug and chemical factories |
| 1,2-Dichloropropane | zero | 0.005 | Increased risk of cancer | Discharge from industrial chemical factories |
| Di(2-ethylhexyl) adipate | 0.4 | 0.4 | Weight loss, liver problems, or possible reproductive difficulties. | Discharge from chemical factories |
| Di(2-ethylhexyl) phthalate | zero | 0.006 | Reproductive difficulties; liver problems; increased risk of cancer | Discharge from rubber and chemical factories |
| Dinoseb | 0.007 | 0.007 | Reproductive difficulties | Runoff from herbicide used on soybeans and vegetables |
| Dioxin (2,3,7,8-TCDD) | zero | 0.00000003 | Reproductive difficulties; increased risk of cancer | Emissions from waste incineration and other combustion; discharge from chemical factories |
| Diquat | 0.02 | 0.02 | Cataracts | Runoff from herbicide use |
| Endothall | 0.1 | 0.1 | Stomach and intestinal problems | Runoff from herbicide use |
| Endrin | 0.002 | 0.002 | Liver problems | Residue of banned insecticide |
| Epichlorohydrin | zero | TT9 | Increased cancer risk, and over a long period of time, stomach problems | Discharge from industrial chemical factories; an impurity of some water treatment chemicals |
| Ethylbenzene | 0.7 | 0.7 | Liver or kidneys problems | Discharge from petroleum refineries |
| Ethylene dibromide | zero | 0.00005 | Problems with liver, stomach, reproductive system, or kidneys; increased risk of cancer | Discharge from petroleum refineries |
| Glyphosate | 0.7 | 0.7 | Kidney problems; reproductive difficulties | Runoff from herbicide use |
| Heptachlor | zero | 0.0004 | Liver damage; increased risk of cancer | Residue of banned termiticide |
| Heptachlor epoxide | zero | 0.0002 | Liver damage; increased risk of cancer | Breakdown of heptachlor |
| Hexachlorobenzene | zero | 0.001 | Liver or kidney problems; reproductive difficulties; increased risk of cancer | Discharge from metal refineries and agricultural chemical factories |
| Hexachlorocyclopentadiene | 0.05 | 0.05 | Kidney or stomach problems | Discharge from chemical factories |
| Lindane | 0.0002 | 0.0002 | Liver or kidney problems | Runoff/leaching from insecticide used on cattle, lumber, gardens |
| Methoxychlor | 0.04 | 0.04 | Reproductive difficulties | Runoff/leaching from insecticide used on fruits, vegetables, alfalfa, livestock |
| Oxamyl (Vydate) | 0.2 | 0.2 | Slight nervous system effects | Runoff/leaching from insecticide used on apples, potatoes, and tomatoes |
| Polychlorinated biphenyls (PCBs) | zero | 0.0005 | Skin changes; thymus gland problems; immune deficiencies; reproductive or nervous system difficulties; increased risk of cancer | Runoff from landfills; discharge of waste chemicals |
| Pentachlorophenol | zero | 0.001 | Liver or kidney problems; increased cancer risk | Discharge from wood preserving factories |
| Picloram | 0.5 | 0.5 | Liver problems | Herbicide runoff |
| Simaziner | 0.004 | 0.004 | Problems with blood | Herbicide runoff |
| Styrene | 0.1 | 0.1 | Liver, kidney, or circulatory system problems | Discharge from rubber and plastic factories; leaching from landfills |
| Tetrachloroethylene | zero | 0.005 | Liver problems; increased risk of cancer | Discharge from factories and dry cleaners |
| Toluene | 1 | 1 | Nervous system, kidney, or liver problems | Discharge from petroleum factories |
| Toxaphene | zero | 0.003 | Kidney, liver, or thyroid problems; increased risk of cancer | Runoff/leaching from insecticide used on cotton and cattle |
| 2,4,5-TP (Silvex) | 0.05 | 0.05 | Liver problems | Residue of banned herbicide |
| 1,2,4-Trichlorobenzene | 0.07 | 0.07 | Changes in adrenal glands | Discharge from textile finishing factories |
| 1,1,1-Trichloroethane | 0.20 | 0.2 | Liver, nervous system, or circulatory problems | Discharge from metal degreasing sites and other factories |
| 1,1,2-Trichloroethane | 0.003 | 0.005 | Liver, kidney, or immune system problems | Discharge from industrial chemical factories |
| Trichloroethylene | zero | 0.005 | Liver problems; increased risk of cancer | Discharge from metal degreasing sites and other factories |
| Vinyl chloride | zero | 0.002 | Increased risk of cancer | Leaching from PVC pipes; discharge from plastic factories |
| Xylenes (total) | 10 | 10 | Nervous system damage | Discharge from petroleum factories; discharge from chemical factories |
Radionuclides
| Contaminant | MCLG (mg/L) | MCL or TT (mg/L) | Potential Health Effects from Ingestion of Water | Sources of Contaminant in Drinking Water |
| Alpha particles | none7 ———- zero | 15 picocuries per Liter (pCi/L) | Increased risk of cancer | Erosion of natural deposits of certain minerals that are radioactive and may emit a form of radiation known as alpha radiation |
| Beta particles and photon emitters | none7 ———- zero | 4 millirems per year | Increased risk of cancer | Decay of natural and man-made deposits of certain minerals that are radioactive and may emit forms of radiation known as photons and beta radiation |
| Radium 226 and Radium 228 (combined) | none7 ———- zero | 5 pCi/L | Increased risk of cancer | Erosion of natural deposits |
| Uranium | zero | 30 ug/L as of 12/08/03 | Increased risk of cancer, kidney toxicity | Erosion of natural deposits |
In China, a large number of communities benefit from reclaimed water. According to Xuejian & He (2009), nutrient levels in recycled water are not monitored and examined meticulously. Even though there are established Standards of Reclaimed Water Quality to control the use of water depending on its application, most of the user, suppliers, and managers tend to neglect specific quality of treated water in thinking that recycled water has a general use. This results in issuing of authorization and permits to use reclaimed water in any application by meeting the lowest quality criteria of reclaimed water. When it comes to safety of reclaimed water, apparently, even wastewater that underwent high-level disinfection can cause acute health problems when standards of drinking water are applied. In China, it is difficult to determine which public places use recycled water due to failure to place a warning sign. As a stated example, reclaimed water from sprinklers in lawns or parks may be used by a pet owner to refresh his dog, or people might wash their faces in the water. Since the quality of reclaimed water is not strictly controlled, it might lead to potential harm to those coming in contact with it. In the use of recycled water in households, customers are given both potable and reclaimed water, increasing the risk of cross-contamination. No regulations have been established in China that requires suppliers to install a backflow prevention device on the drinking water supply line (Xuejian & He 2009).
Chinese regulations also grade water for human consumption on a scale of one to five, with a grade of one as the highest meaning the water is pure and five as the lowest grade meaning the water is heavily polluted. A class three grading is the minimum acceptable grade of water quality for human consumption (Lague 2005). The water quality classification in China is based on its application and target and follows the Environmental Quality Standard GB3838-2002. The water quality classification in China is shown below in Table 2 as taken from < http://siteresources.worldbank.org/INTEAPREGTOPENVIRONMENT/Resources/China_WPM_final_lo_res.pdf> (The World Bank 2006).
Table 2
| Grade I | Mainly applicable to the source of water bodies and national nature preserves |
| Grade II | Mainly applicable to class A water source protection area for centralized drinking supply, sanctuaries for rare species of fish, and spawning grounds for fish and shrimps |
| Grade III | Mainly applicable to class B water source protection area for centralized drinking water supply, sanctuaries for common species of fish and swimming zones |
| Grade IV | Mainly applicable to water bodies for general industrial water supply and recreational waters in which there is no direct human contact with the water |
| Grade V | Mainly applicable to water bodies for agricultural water supply and for general landscape requirements. |
| Grade V+ | Essentially useless |
In Japan, recycled water is used for several purposes like toilet flushing and snow melting. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) established national guidelines and rules based on studies by Wastewater and Sludge Management Division in 2005 for the use and application of reclaimed water. The Wastewater and Sludge Management Division carries out studies on low-cost treatment methods of wastewater in Okinawa, Japan as well as regularly assessing pollution load to surface water in India to identify possible areas where water quality can be improved. They are also responsible for investigating the treatment of wastewater, with close attention to incidents of pathogens in water, causes of endocrine disruptors, technical principles in treated wastewater recycling systems, and the effects of wastewater overflow on aquatic ecosystems (National Institute for Land and Infrastructure Management n.d.). To ensure the quality of treated wastewater in Japan, they have adopted the National Effluent Standards in 2007. These standards include two categories, namely for protecting human health and for protecting the living environment. Table 3 and 4 below from < http://www.env.go.jp/en/water/wq/nes.html>, shows the national effluent standards on toxic substances and their acceptable limits (Ministry of Environment Government of Japan 2007).
Table 3
Items Related to The Protection of Human Health
| Toxic Substances | Permissible Limits |
| cadmium and its compounds | 0.1 mg/l |
| cyanide compounds | 1 mg/l |
| organic phosphorus compounds (parathion, methyl parathion, methyl demeton and EPN only) | 1 mg/l |
| lead and its compounds | 0.1 mg/l |
| sexivalent chrome compounds | 0.5 mg/l |
| arsenic and its compounds | 0.1 mg/l |
| total mercury | 0.005 mg/l |
| alkyl mercury compounds | Not detectable |
| PCBs | 0.003 mg/l |
| trichloroethylene | 0.3 mg/l |
| tetrachloroethylene | 0.1 mg/l |
| dichloromethane | 0.2 mg/l |
| carbon tetrachloride | 0.02 mg/l |
| 1, 2-dichloro ethane | 0.04 mg/l |
| 1, 1-dichloro ethylene | 0.2 mg/l |
| cis-1, 2-dichloro ethylene | 0.4 mg/l |
| 1, 1, 1-trichloro ethane | 3 mg/l |
| 1, 1, 2-trichloro ethane | 0.06 mg/l |
| 1, 3-dichloropropene | 0.02 mg/l |
| thiram | 0.06 mg/l |
| simazine | 0.03 mg/l |
| thiobencarb | 0.2 mg/l |
| benzene | 0.1 mg/l |
| selenium and its compounds | 0.1 mg/l |
| boron and its compounds | Non-coastal areas 10 mg/l Coastal areas 230 mg/l |
| fluorine and its compounds | Non-coastal areas 8 mg/l Coastal areas15 mg/l |
| ammonia, ammonium compounds, nitrate and nitrite compounds | 100 mg/l (Total of ammonia,-N multiplied by 0.4, nitrate-N and nitrite-N) |
Table 4
Items Related to The Protection of The Living Environment
| Living Environment Items | Permissible Limits |
| hydrogen ion activity (pH) | Non-coastal areas 5-8-8.6 Coastal areas 5.0-9.0 |
| Biochemical Oxygen Demand (BOD) | 160 mg/l (Daily Average 120 mg/l) |
| Chemical Oxygen Demand (COD) | 160 mg/l (Daily Average 120 mg/l) |
| suspended solids (SS) | 200 mg/l (Daily Average 150 mg/l) |
| n-hexane extracts (mineral oil) | 5 mg/l |
| n-hexane extracts (animal and vegetable fats) | 30 mg/l |
| phenols | 5 mg/l |
| copper | 3 mg/l |
| zinc | 2 mg/l |
| dissolved iron | 10 mg/l |
| dissolved manganese | 10mg/l |
| chromium | 2 mg/l |
| number of coliform groups | Daily Average 3000/cm3 |
| nitrogen | 120 mg/l (Daily Average 60 mg/l) |
| phosphorus | 16 mg/l (Daily Average 8 mg/l) |
The National Institute for Land and Infrastructure Management formulated a new criterion for the reuse of treated wastewater in Japan in the year 2007, as cited by the National Institute for Public Health Japan. Table 5, from < http://www.niph.go.jp/soshiki/suido/pdf/h19JPUS/ abstract/r12.pdf> shows these new criteria with regard to toilet flushing, sprinkling, landscape use, and recreational use.
Table 5
Background of Hong Kong
Hong Kong is a special administrative region of the People’s Republic of China. It is located on the southeastern tip of China, enclosed by the Pearl River delta and South China Sea. Between Hong Kong and the Kowloon Peninsula is one of the world’s most known deep-water harbors, Victoria Harbour. In 2008, the population in Hong Kong was approximately 6.8 million. Population in Hong Kong continues to increase due to entry of immigrants from Mainland China. Climate in Hong Kong is sub-tropical, with a temperature below 10 degrees Celsius during wintertime, and more than 31 degrees Celsius in the summer.
Hong Kong and Water Recycling
According to Mrs. Carrie Lam (2009), Secretary for Development in Hong Kong, the Dongjiang River in Guangdong Province gives much of its raw water supply, capable of meeting 70-80% of the water supply. In spite of a steady and stable water supply, the Total Water Management Strategy was implemented to prepare Hong Kong in times of ambiguity and crisis, such as climate changes and low rainfall. According to Lam, it was a duty and obligation of Hong Kong to contribute in the conservation of water and encourage maintainable use of water, especially with the fast population growth in the region. They would give all their effort in preserving, protecting, and saving valuable water resources through the implementation of strategies in management, encompassing conservation, recycling, and development of other water resource options and substitutes.
Several measures have been taken in developing seawater desalination using osmosis technology as one option, while water reclamation trials have been started in areas where the use of seawater for flushing is uneconomical. The Government will also conduct trials of grey water reuse as well as rainwater harvesting for public work projects.
A project is also in place to change and repair about 40% of the water mains, due to be finished by the year 2015. Modernization of water treatment technology is also in the way, through implementation of ozonization and membrane technology in treatment facilities and by improving monitoring and control through further automation (Hong Kong Government 2009).
Urban Uses of Recycled Water
There are several uses of recycled water, whether industrial, agricultural, or even urban. Table 6 below shows a list of applications of reclaimed water in an urban setting. This includes irrigation, commercial use, ornamental purpose, and fire protection (North Carolina AWWA/WEF 1996).
Table 6
Urban Uses of Recycled Water
| Irrigation – Reclaimed water is rich in nutrients, making fertilizer use unnecessary | Parks, athletic grounds, school yards, highway medians and shoulders, and spaces surrounding public buildings and facilities; private landscaped areas in commercial and industrial buildings, golf courses, and nurseries; habitats in family dwellings; private landscaped areas in commercial and industrial buildings, golf courses, and nurseries |
| Commercial Use | Washing vehicles, washing windows, water for application of biocides and liquid fertilizers, concrete production in rapid-mix and on-site uses
|
| Ornamental Use | Fountains, reflecting pools, enhancing flow in urban streams
|
| Toilet and Urinal-Flushing | Commercial, industrial, and residential buildings especially in multi-story facilities |
| Fire Protection | Potable water lines are sized only to deliver it, avoiding degradation of water quality in pipelines due to long length of time |
Reclaimed water indeed has a lot of urban uses. The potential level of exposure of reclaimed water, however, dictates the class that is suitable for urban or municipal reuse. Several factors affect the potential level of exposure, which include distance from residential or public access area, use of signs or fences to restrict access to the site, method of irrigation utilized, and the use of restricted watering times. Class A reclaimed water may be used for residential and municipal reuse because of the high potential for exposure to humans due to accessibility to public areas. On the other hand, Class B and C reclaimed water may be used in municipalities where public access is and can be controlled. Class D water is not suitable at all for urban non-potable applications. As mentioned earlier, the method of irrigation also affects the class assigned to reclaimed water and how much control over public access in needed. For municipal irrigations, the quality limit on reclaimed water is in the use of spray irrigation. However, if methods such as subsurface, trickle, or micro-irrigation systems are used, a lesser class of reclaimed water may be allowed as long as it poses no threat to public health and no contaminated run-offs take place (EPA Victoria 2003).
Hong Kong and Application of Recycled Water in the Urban Setting
In Hong Kong, as opposed to different countries, water reclaiming is still in its early stages. There have been several pilot schemes with regard to wastewater treatment, and its applications are still being discovered and manipulated.
Internationally, uses of recycled water include cleaning roads and vehicles, irrigation of parks and fields, landscaping, and urban development among others. The use of reclaimed water has decreased environmental pollution and lessens the requirement and demand on freshwater sources. It does not only support the economy and development of various countries, but it also helps in protecting the environment.
In the year 2005, the Drainage Services Department of Hong Kong introduced its pilot plan of using reclaimed water in Ngong Ping Sewage Treatment Works (NPSTW) which began its operation then. It is the first tertiary plant in Hong Kong that uses advanced chemical, biological, filtering, and disinfection processes. As a result, purified, odorless, and safe reclaimed water for non-potable applications was created.
The reclaimed water produced from NPSTW is used for toilet flushing in nearby public toilets, in rearing aquarium fish, and for controlled irrigation. Experience, observations, and information obtained from the pilot run were used to develop other options in application of reclaimed water (Drainage Services Department 2009).
The NPSTW project’s goal is to build sanitation facilities for the entire Ngong Ping region of Lantau Island, in order to meet the demands of current and potential expansions. It entails the installation of a sewage collection facility, a sewage treatment works (STW) to provide biological and tertiary treatment with disinfection, the establishment of sludge treatment and disposal areas, and the construction of a pipeline to convey treated effluent from the STW to Tai O for disposal (Hong Kong Environmental Protection Division n.d.).
Treated sewage effluent (TSE) is used to supply public toilets in Ngong Ping as well as toilets in the cable car terminal. Potentials in use for irrigation, cooling, and water display are also being tested. To ensure safety of the reclaimed water, the tertiary level of treatment is applied to wastewater. Table 7 below shows a list of the different processes utilized in the treatment plant (Hong Kong Water Supplies Department n.d.). An illustration showing the process at NPSTW is shown in Figure 4 (Chartered Institute for Water and Environmental Management n.d.).
Table 7
| Major Sewage Processes Utilized in The Treatment of Water |
| Screening Grease Removal Biological Activated Sludge Processà sequencing batch reactor (SBR), nitrification, denitrification, tertiary filtration, UV disinfection |
The use of sequencing batch reactor (SBR) in the Ngong Ping Sewage Treatment Plant offers greater flexibility in dealing with increased fluctuations in sewage flow during weekdays and holidays because a continuous operation mode is not required. It is also the most applicable method to use in consideration of the available land area, treatment level required, plant scale, experience, and the cost of maintenance and operations. In addition, a second chlorination device was built to boost the amount of chlorine in the reclaimed water used in public restrooms, cable car production, and other applications. Pressure, sludge thickening, sludge digestion, and sludge dewatering are some of the sludge treatment methods that are included.
Figure 4
When it comes to water applications and uncontrolled irrigations, further treatments based on 1California 2001 standards are applied. The main goal of these requirements is to provide pathogen-free processed waste effluent in order to avoid any additional health effects from human interaction. Coagulation, granular, and membrane filtration are all necessary treatment procedures, accompanied by disinfection using chlorine or UV disinfection technologies.
A health concern in the use of TSE is primarily focused on diarrheal diseases related to accidental consumption of inadequately treated water. Several precautions have been established as summarized in Table 8 (Hong Kong Water Supplies Department n.d.).
Table 8
| Precautionary Measures For TSE Reuse |
| 1) To distinguish the TSE water supply and distribution system from fresh water supply and distribution systems, all piping and fittings will be purple in colour. Which prevents cross-connection and, as a result, pollution.
2) Routine checks will be conducted to ensure that the TSE supply and distribution systems are not connected to the fresh water supply and distribution system. This task requires the use of a non-toxic dye.
3) Permanent caution signs may be posted in places where public access to TSE is practicable, with the exception of toilets, to inform everyone that handled effluent is being used and is not suitable for consumption. |
[6]
In the year 2006, as part of the government’s Total Waste Management program, a second pilot project at the Shek Wu Hui Sewage Treatment Works began its operation. The reclaimed water is used to supply water to chosen users like schools, elderly homes and village houses. Reclaimed water served its purpose in toilet flushing, unrestricted irrigation, and used decoratively in streams and fountains. Again, information obtained from the project provided data on how else reclaimed water can be made use of in Hong Kong.
Since the 1980s, Shek Wu Hui Sewage Treatment Works (SWHSTW) has been in service. It handles wastewater from Fanling Sheung Shui before discharging it into the Mai Po Inner Deep Bay Ramsar Site through the Indus River and the Shenzhen River. The 2006 project is an extension of SWHSTW’s treatment capability in order to accommodate rising wastewater flow and load due to the area’s growing population. It has expanded the sewerage grid into previously unserviced regions. The scheme included the construction of two flow division pump pits, one bioreactor, two sedimentation ponds, and a sludge dewatering house expansion, as well as the revision of sludge thickening and dewatering facilities, as well as the provision of electrical and mechanical equipment to assist proposed treatment facilities and the repair of existing treatment plants (Drainage Services Department 2005).
Though Hong Kong still has a long way to go to catch up to countries that have already established a reliable method of treating wastewater for utilization in the community, the effort is there to learn, to observe, and to gain new insight on potential uses of recycled water.
In Hong Kong, several applications of reclaimed water are seen as a potential. After all, reclaimed water in different countries is also used in similar ways. In urban areas, it can be used for toilet flushing, irrigation of landscapes and parks, and for decorative purposes in fountains. There are endless possibilities of using reclaiming water in urban areas. The important thing, however, is to ensure that a safe and reliable system is utilized in treating wastewater. This would guarantee a harmless approach in different applications. Treatment facilities need to be constantly monitored and checked, and managers of these plants should be well aware of the rules and guidelines set by appropriate authorities and agencies regarding the use and treatment of wastewater for reuse.
Water is truly precious and humans cannot survive without it. Even in the light of advanced treatment and water recycling, it is useless if we do not start taking care of it by being more conscientious in its use and by taking measures to maximize the supply that we have. If man does not take care of his environment, it will turn against him in the future. We are already suffering numerous blows from the global economic crisis to the climate change. It is essential that we take care of what we have now before it runs outs.
Through the appropriate use of water recycling, it can prevent bodies of water from being overused, spent, or polluted. Water recycling gives us a new hope, a chance at repairing all the damages that we have done to nature. It provides us with another option and a new way of getting a stable water supply, not only for us, but for future generations.
Hopefully, in the future, more uses of reclaimed water can be discovered with the advancement of technology and with wisdom gained from experience. As long as everyone is willing to help out each other, to support a good cause, and be more mindful of individual actions, there is hope after all for our world.
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- 4 Andrade, A et al. 1999 cited in Southwest Florida Waste Management District Reclaimed Water n.d.
- 5 Metcalf & Eddy 2007 Southwest Florida Waste Management District Reclaimed Water n.d.
- 6 Cross, P. n.d. cited in Southwest Florida Waste Management District Reclaimed Water n.d.
- 7 Metcalf & Eddy 2007 Southwest Florida Waste Management District Reclaimed Water n.d.
- 8 Monterey Regional Water Pollution Control Agency 2009 cited in Southwest Florida Waste Management District Reclaimed Water n.d.
- 9 Metcalf & Eddy 2007 Southwest Florida Waste Management District Reclaimed Water n.d.
- 10 York, D.W. 2006 cited in Southwest Florida Waste Management District Reclaimed Water n.d.
- 3 United States Environmental Protection Agency 2009
- [5] CDM 1980 cited in Southwest Florida Waste Management District Reclaimed Water n.d.
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- [6] California 2001 Water Recycling Criteria cited in Hong Kong Water Supplies Department n.d.
