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Water Efficiency Series: Part 3- Water Scarcity, Awareness and Rainwater Harvesting
When looking at a map it appears that we have more than enough water to sustain all of the earth’s inhabitants with plenty of clean water. However, less than 1% of this water can meet human’s freshwater needs. (Source: Sherwood Institute Blog “All the Water in the World”, Aug. 25 2010). At present there are water wars in countries around the globe because of the scarcity of the valuable resource. Meanwhile, in many countries (such as the U.S.) we are over-using water without even thinking about it.
My best friend lives in St. Thomas. When I visited her last year, I was amazed that ALL of the water she used was rainwater from a rooftop catchment system. I was there for 10 days and in that time quickly adapted to “West Indian Showers” (turning on the water only for a few seconds at and the beginning and end of your showering process), using the absolute minimum amount of water for dishwashing, and learned the phrase “in this land of fun and sun, we don’t flush for number one!”
Although the island life takes a little getting used to, when I returned home I was SO conscious of just how much we, as a society, waste water. My roommate would defrost chicken by running cold water over it- for hours! Despite my complaints and explanations of why it was wasteful, she couldn’t understand that water is a precious resource.
Compared with other developed countries, the United States has some of the lowest water/wastewater costs as a percentage of household income. I know that when I became responsible for paying gas and electricity bills, our thermostat turned down and I became much more conscious of conserving energy. As a renter, I have still never had a water bill in my name, as is the same for most young people. Water seems free, and even for my landlord who is footing the bill; it is a very low cost utility.
At present, the cost of water does not reflect the value of the resource. Water infrastructure is aging and revenue generated from the sale of water is needed to improve water services. Increasing the price of water will not only generate revenue to improve the infrastructure but should also help to make the public understand that water is a valuable and precious resource.
In the United States, we are lucky to have infrastructure for delivering water conveniently and cheaply to our faucets. However, it takes a huge amount of energy to transport and treat water. Rainwater is an under-utilized resource that can be used as potable water without extensive pumping and treatment.
In many areas of the world, rainwater is used for everything: showering, drinking, dishwashing, irrigation and toilet flushing. However, in developed countries, which do have advanced water infrastructure, rainwater is generally used only for non-potable uses such as irrigation, toilet flushing, laundering, emergency water supplies, fire prevention use and process water uses.
Rainwater harvesting is a very scalable technology that can be as simple as catching rainwater from the roof and delivering it to storage tanks for irrigation or can be as complex as a large cistern with treatment processes for indoor use. It is important to match the rainwater use to the level of treatment provided. Water used for irrigation does not need to be treated to potable water standards, as that would be a waste of time, energy and money. However, if the water will be used indoors, it is important to insure that it is adequately treated to mitigate health concerns.
There are so many benefits of rainwater harvesting! These include (but are not limited to): minimizing stress on municipal systems (supports supply and reduces infrastructure maintenance costs); reducing energy required for treatment and pumping of centralized systems (thereby reducing greenhouse gas emissions); providing independent water security especially in times of natural disaster; often providing cost savings over time; decreasing municipal stormwater intake (thus reducing flooding, lessening quantity of stormwater needing treatment, and minimizing sewer overflow); and offering community benefits such as open green areas, public water awareness and self sufficiency.
Although using rainwater can be very beneficial, it is important that the catchment systems are designed well and with caution. Most concerns are related to health concerns from biological or chemical contamination. However, in good designs most of these worries are minimized. It is important that municipalities recognize the benefits of rainwater harvesting and create guidance to encourage safe catchment system design. Equally important is for citizens to use these regulations when building a system. Lastly, it is important that systems are inspected regularly to insure against contamination and to ensure that the water stays at a healthy pH level.
In conclusion, it is important to grow awareness in many developed countries about the scarcity of water. One way of doing this is by raising water prices to full-cost pricing. Once people become more conscious that we need to look at other water sources, hopefully rainwater harvesting will become more popular. Rainwater catchment systems are very scalable and have many benefits, but most be designed cautiously to ensure the rainwater remains safe. Hopefully, systems will become more prevalent to reduce the impact on current infrastructure and to ensure security to our water systems.
Pictures from an “Eco-resort” near Beijing
A few weeks ago, I visited an eco-resort outside of Beijing. The resort promoted fishing and freshwater crabbing in stocked ponds, but when I ventured to a far corner of the man-made pond, I saw about a dozen dead fish floating in the water. Here are some photos:
Eco-travel, eco-vacations, and eco-resorts are all hot words right now in China, which is good, in that people are starting to be more aware of the importance of nature. But images like the ones above are a reminder that along with the new vocabulary, some major improvements need to be made in the actual quality of the environments here. Guests should be aware that sometimes, the letters “e-c-o” in front of something may not have much meaning.
A Closer Look at Water Issues in Bangalore
A study taken by the Centre for Symbiosis of Technology, Environment, and Management (STEP) approximated that 40% of the population of Bangalore is dependent on groundwater. There are around 125,000 private bore wells in the city. Because the extraction of groundwater is highly unregulated, the water tables have been rapidly depleting. According to R. Vasudevan, a chief engineer of the Bangalore Water Supply and Sewerage Board (BWSSB), the water levels have dropped 300 feet below ground level. The BWSSB extracts the majority of the water they distribute from the Cauvery River. This river is located almost 100 km away from the city and at an altitude of about 1,500 feet below that of the city. Because of this, approximately 75% of the total BWSSB revenue is spent on electricity charges. Another huge problem exists – almost 30% of the water extracted is lost to corroded and broken piping systems. The piping system in the city is over 50 years old. Many of the pipes are in horrible condition, producing many leaks. Unfortunately, the BWSSB has only made temporary fixes to repair the decaying pipes rather than to replace them entirely.
With such water shortages looming over the city, it is essential for changes in the water policy of the city to take effect. The BWSSB has just mandated rainwater harvesting last year as an amendment to the Bangalore Water Supply and Sewerage Act of 1964. The amendment states that all buildings with a total rooftop area of 2400 square feet or greater must install a rainwater harvesting system; all proposals for buildings with a total rooftop area of 1200 square feet or greater must include plans for a rainwater harvesting system. In order to see how effective rainwater harvesting can be, I have prepared a basic water balance of the city. The following values necessary for a balance were found. Some of the metrics were determined by simple calculations.
|Area of the City||
|Amount of Average Rainfall||
|TOTAL Amount of Rainfall in the City, Annual||
Water Demand Data:
Per Capita Water Demand*
|Population of the City||
|Water Demand for Domestic Use, Annually||
|Daily Water Demand for Other Uses**||
|Water Demand for Other Uses, Annually||
|TOTAL Water Demand, Annually||
*Please Note: This value is standard set by the Central Public Health and Environmental Organization. However, this is an overestimate of the per capita water use daily. Studies show that many people use only around 100 L of water per day.
**Please Note: This value encompasses the demand for commercial establishments, industrial users, institutional users, grounds (municipal and industry), fountains, and unaccounted for water (leakages). This data was gathered from surveys and interviews. The values were obtained from the Resource Optimization Initiative:
Eckelman, M. J., Shenoy. M., Ramaswamy, R., Chertow, M. 2010. Applying industrial ecology tools to increase understanding of demand-side water management in Bangalore, India. (unpublished manuscript).
If we look at the total amount of rainfall on the city and the total water demand, we see that the total rainfall is only slightly greater than the total water demand. We must take several things into account. First of all, it is not possible to capture 100% of the total rainfall. If we approximate that 70% of the total rainfall can be effectively captured to recharge aquifers, lakes, and bore wells, then the total water demand exceeds the amount of rainfall captured. This shows the severity of the water shortages in Bangalore. The numbers are too close to each other for comfort!
In order to alleviate the water scarcity issues, a greater campaign to install rainwater harvesting units should be invested in. People should be made aware of the advantages that rainwater harvesting can have. In addition, the BWSSB should work to expand their water reuse programs. Currently less than 1% of water is recycled for reuse. More sewage treatment plants should be installed to increase this percentage. There are many ways to solve this water crisis. Small steps can yield large results. Installing a rainwater harvesting system can be as cheap as 400 Indian Rupees (Approximately $8.50). The installation of such units will help both the people and the environment. The citizens of Bangalore can reap the benefits of sustainable water management while the environment can enjoy its water sources being replenished.
Decentralized Wastewater Treatment, Puducherry, and Japan’s Johkasou
Two weeks ago we published an article describing the open sewage systems in Puducherry, a Union territory in South India. In these systems, wastewater from businesses and homes is simply released into the environment with little to no treatment. This release poses a threat to public health and local water quality.
The conventional method of wastewater treatment requires a network of pipes and sewer lines that feed into a centralized wastewater treatment plant. After treatment, the water is expelled to a nearby body of water or used as reclaimed water. The conventional method often requires a central authority (e.g. a city government) to organize construction of sewer lines and connect users to the public system. After that, the authority must ensure that the treatment plant continues to operate correctly.
It is challenging to build and maintain a functioning wastewater treatment plant. In the United States we often take the operation of wastewater treatment plants for granted –the US has a strong regulatory system which ensures that municipalities and governments keep their services running as promised. In countries with less accountability in government (a consequence of corruption, holes in public policy, civil unrest, economic problems, a weak judicial system, etc.), centralized disposal systems are difficult to implement successfully. In Ghana, for instance, many wastewater treatment plants are constructed and then abandoned after just a few years of operation.
One alternative to utilizing a centrally controlled conventional treatments system is utilizing a decentralized array of smaller treatment systems. According to Small & Decentralized Wastewater Management Systems, decentralized wastewater management may be defined as the collection, disposal, or reuse of wastewater from individual homes, clusters of homes, isolated communities, or parts of existing communities at or near the point of wastewater generation. By having an array of decentralized treatment systems, regions are less susceptible to a total failure of wastewater treatment. The failure of one centralized system will stop treatment on a large scale. The failure of one decentralized system will only affect a small group of people.
Japan’s Miniature Wastewater Treatment Plants: Johkasou
The Puducherry Pollution Control Committee has decided to adopt a solid waste management scheme similar to Japan’s model. In the realm of wastewater treatment, the PPCC should also consider one of Japan’s approaches to decentralized wastewater treatment: the “johkasou.”
A johkasou is a wastewater treatment tank. It looks like a septic tank, but it behaves like a miniature wastewater treatment plant. The technology that engineers have fit into these small tanks is impressive –a small-scale johkasou for an individual house might sport an anaerobic filter tank, contact aeration tank, sedimentation tank, and disinfection tank. All of these treatment tanks can be held in a main tank as small as 4 cubic meters, and once water undergoes johkasou treatment it can be used for non-potable applications or released directly to the environment.
According to the Japan Sanitation Consortium, johkasou require electric energy comparable to the energy needed to light a room (a system designed for 5 people will consume about 37 kWh per month –the same amount of energy consumed by a 60 W lightbulb kept on for 26 days straight). Johkasou are intended for areas with limited access to centralized sewage systems. Because the tanks require electricity to operate, they cannot be used in areas that lack reliable electricity supply.
Installing a johkasou typically requires one week of construction work. The cost to purchase and install a 5-person johkasou is about ¥860,000, or nearly $10,000. Depending on the region, the Japanese government has subsidized between 40% to 90% of this cost for homeowners and businesses interested in having a johkasou.
Why would the Japanese government subsidize up to 90% the cost for a small-scale system? Release of untreated wastewater into the environment can threaten the fishing industry and increase water treatment costs downstream. Also, threats to public health increase healthcare expenditures and can hinder productivity (sick people are less productive). The economic benefits of decentralized wastewater treatment coupled with a cultural desire to protect Japan’s environment make it appealing for the government to subsidize johkasou programs.
Is a conventional wastewater treatment system feasible in Puducherry? In 2007, only about 30% of the urban area had sewage service. The other 70% discharged wastewater to the environment via exposed channels or septic tanks.
The costs associated with the conventional system and the johkasou decentralized systems are high. One must study the Puducherry hydrology, its political climate, its economic system, and its culture before a decision can be made. Centralized systems? Or decentralized systems? Or both?
In 2005, 35 million people in Japan (about 27% of the country’s population) used johkasou tanks. The technology is widely used, and it may offer regions like Puducherry a way to clean its wastewater without centralized treatment systems. Other cheaper alternatives to the johkasou include natural treatment systems like treatment wetlands and ponds. Unlike a johkasou, however, a natural treatment system often requires more land area than highly urbanized areas can provide.
To learn more about johkasou use in Japan, visit the Japan Education Center of Environmental Sanitation website here.
Brief Introduction to Beijing’s Gaobeidian Wastewater Treatment Plant
Beijing Gaobeidian Wastewater Treatment Plant is not only the largest of Beijing Municipality’s 15 wastewater treatment plants; it is also currently the largest wastewater treatment plant in China. It serves a population of 2.4 million people and has a daily capacity of 100,000 cubic meters (26.4 million gallons/day), processing about 40% of Beijing Municipality’s total wastewater volume. When the plant was built in the 1990’s, national standards for phosphorous and nitrogen in treated effluent had not yet been set, so that treated wastewater did not meet criteria for even the national level V (not suitable for use in agriculture) surface water standard because of high levels of nitrogen and phosphorous. Since then, the plant’s secondary treatment facilities are undergoing modifications which will allow approximately 530,000 cubic meters/ day to be treated to national 4 standard for surface water (suitable for industrial use and other uses not in direct contact with humans) and 470,000 cubic meters/day to be treated to national 3 standard for surface water (suitable for aquaculture and recreation purposes) In the US, mostly all WWTPs’ effluents meet China’s Level II standard for surface water.
In addition to its primary and secondary treatment facilities, Beijing Gaobeidian WWTP also boasts facilities to process and collect the methane gas produced during the anaerobic digestion processes. According to the plant’s materials, a portion of the generated biogas is used internally to make the Gaobeidian’s wastewater treatment processes even more energy efficient (for example as a substitute for natural gas to heat the wastewater digesting processes), and the rest is sold back to Beijing’s energy grid. Some background information about how methane gas generated from wastewater treatment is utilized in the US can be found here.
Built as a demonstrative example for wastewater treatment all over China, Gaobeidian WWTP also has a greenhouse ecosystem on premise that utilizes the Level III standard effluent to as a reclaimed water source. According to reports, after the Beixiaohe WWTP (one of the 15 originally planned WWTP plants for Beijing’s development) was completed in 2007, Beijing reached a reclaimed water usage rate of 50%. As mentioned in a previous post, there are also more and more regulations being passed about the usage of reclaimed water for landscaping and waterscaping purposes in Beijing. As such regulation develops, it is critical that the appropriate advances in wastewater treatment technology are made in order to support such regulation.
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