VIP Latrine Design Analysis

  To gain understanding and practice in dealing with sanitation issues in developing regions a design analysis of an Ventilated Improved Pit Latrine. The design analyzed can be found here Design Plans.

  In order to determine if the original design is large enough, the number of people served for various design lives were calculated. Only the rectangular area under the user-interface hole (not the side square with the access door) was included in the pit volume calculations because solids would not fill the area under the access door. Also, a 0.5 m dead space was assumed between the top of the solids and the superstructure. This results in the dimensions of the original being 0.7 m x 1.6 m x 1.1 m and a volume of 1.2 m. A solids accumulation rate for a dry pit of 0.06 m³/person/yr was assumed.

  If the family served was assumed to be 4 people, the design life of 5 years is sufficient. These calculations show the original pit volume is sufficient for a family of 4; however, the shape of the pit is a problem. In order to clean the pit, someone must climb into a 0.8 m x 0.8 m x 1.6 m area and then reach around a corner in order to reach the area where solids accumulate. This would be a cramped and dirty task for any adult. In order to improve the pit, the shape of the pit is changed into a rectangle, where the access door would be above the area where solids accumulate so they can be shoveled or mechanically removed from outside of the pit. The proposed design is 0.8 m wide x 2.8 m long x 1.6 m deep. This depth includes dead space. This volume, 2.5 m³ is still sufficient for the family of 4 for five years, but now is easier to remove the solids. See Appendix 1 for plans of the revised pit layout and superstructure.

 The second revisions are to the materials of construction. While steel corrugated roof is an acceptable material, it may not be easily repaired or replaced by locals in rural South America. It also is more expensive than local materials. It is suggested the roof be changed to a thatch roof made with local materials to make it easier for locals to maintain and replace if necessary.

  It is also suggested the vent pipe material be changed for similar reasons. PVC pipe can become brittle when exposed to high sunlight but stabilized PVC can be expensive and difficult to come by. In order to make the vent easy to maintain and replace it is suggested to be a cement-rendered reed pipe.

  The current design appears to require the use of a door for privacy and the adobe walls and steel roof do not provide for much ventilation. In order to fix both problems, the shape of the superstructure has been revised. A square spiral structure has been designed for the revised superstructure. See figures in Appendix 1 for superstructure plan.

Improved Design Plans

Superstructure Profile

Superstructure Front

Superstructure Plan

Slab Plan

Pit Plan

Case Study: Recharge Pits

  As surface waters become more polluted, a greater fraction of the world’s water supply is becoming dependent on groundwater. Simple pump wells are cheap and simple solutions to supply groundwater and are increasingly common among developing regions. The groundwater supply is limited however, and, as urbanization begins to concentrate population, water demand often is greater than the recharge rates of groundwater sources. This creates an unsustainable practice of groundwater dependence that could eventually result in the depletion of aquifers, causing a myriad of consequences including water scarcity in regions that need it most.

  Recharge pits are a simple technology that contributes to the effort of increasing recharge rates and extending the lifespan of groundwater supplies. These pits, and similar recharge techniques, are especially valuable in urbanized areas where development further limits infiltration. They can also be viewed as a type of water treatment technique as this infiltration works much like filtration, screening solids and other contaminates. Groundwater table maintenance is necessary to provide continued water sources as well as to protect existing infrastructure from damage due to soil matrix collapse. 

Technology

 

  Recharge pits and trenches are a rainwater harvesting technology that combines with groundwater recharge, collecting precipitation and runoff and storing it in the groundwater table for future use. Rainwater is collected from roofs of houses and community structures in order to minimize the recharge pit footprint while maximizing collection area. This water is transferred directly to the recharge pit or trench. The pit is generally 1 to 2 m wide and 2 to 3 m deep, an unlined excavation filled with boulders, gavel, and coarse sand from the bottom up in order to provide filtration while minimizing evaporation loss. Recharge trenches are 0.5 to 1 m wide and 1 to 1.5 m deep, spanning between 10 to 20 m in length depending on hydraulic load. Ground water recharge supplements shallow aquifers, increasing ground water supply beyond the capacity of mismanaged rainfall. The water collected from catchments built on impervious surfaces is routed to these highly transmissive recharge pits where it is stored, progressively infiltrating into the soil beyond the duration of the rainfall. This water is later extracted from the groundwater table through existing method according to demand.

  Cost is minimal and consists of excavation and filling material cost as well as catchment construction. In somewhat developed regions with a ready supply of manual labor, such as India, cost can be estimated at less than 100 USD and 100-200 USD for recharge trenches. As location changes labor cost and material rates will undoubtedly vary, soil types can change costs dramatically as well. As excavation increases in difficulty a higher volume of manual labor will be necessary as well as the number of pits due to the limited infiltration rates associated with low permeability soils. Maintenance costs are also minimal. These duties include the replacement of the coarse sand layer, typically after each wet season, in order to allow for effective transport through the sand layer which becomes clogged as it acts to filter receiving water.

  Recharge pits and trenches are best built in areas with water runoff present and shallow, unconfined aquifers. The pit should be placed in close proximity to its associated catchment or catchments as the catchment system should covey collected water directly into the pit. Areas near wells are also helpful in increasing infiltration rates due to the draw-down that results from pumping. These solutions are most effective when surface waters are somehow compromised or inadequate. In areas prone to flood events recharge pits can reduce related hazard by increasing runoff capacity through storage. The increased head associated with groundwater recharge can prevent sea water intrusion into fresh water aquifers. Groundwater is also improved due to the fact that rainwater is free of organics and bacteriologically safe.

 

   Recharge pits are typically either circular or rectangular and 1 to 2 m in width and 2 to 3 m deep. For a single square pit with a width of 1.5 m and depth of 2.5 m with 60% boulder, 20% gravel, 15% sand and 15% unfilled space yields about 2.6 m³ of storage when calculated using typical void ratios and the equation: Vs*e=Vv. Evaporation is negligible due to the filled pit design; therefore the total of the stored water will eventually reach the groundwater table. Infiltration rates vary greatly with soil characteristics and hydrological conditions and it is therefore difficult to estimate common values for the rate of infiltration. For type D clay soils, those typical to North Carolina, infiltration rates are typically between >0.1 m/d for sandy soils these values can be as high as 10 m/d. The unlined sides of the recharge pit work to encourage infiltration, allowing a greater surface area for water influx. The volume, associated catchment area and number of pits must be tailored to their location. Effective designs must take the groundwater table into account when designing these recharge pits. Seasonal highs and lows must be known as shallow groundwater tables are ideal for this technology, but not if they rise above the bottom of the pit. Soil profiles are also highly beneficial, though local knowledge will usually suffice. Regardless the pits should be sized and positioned in such a way as to encourage infiltration, which soil properties largely determine. Soil properties also effect excavation stability which is especially important regarding worker safety during construction. When designed to handle an areas capacity this technology can effectively capture and store available rainwater through largely natural processes in a highly sustainable way.

  Soil clogging is the primary problem with recharge pits and many artificial groundwater recharge systems and designs must take this into account. The top sand layer of a recharge pit acts much like a filter bed, removing suspended solids. Because of this upper sand layer clogging of pit boundaries is avoided and does not need maintenance. When operating effectively, this naturally treats rainwater and runoff and works to improve groundwater quality. If not maintained, these sand layers can become clogged by sediment and algae decreasing effectiveness of the recharge pit by preventing runoff inflow and causing the pit to backup. Clogging is caused by physical processes such as the accumulation of solids present in the received water and the downward movement of fine sand particles causing an uneven distribution of particle size. These processes form thin layers of low permeability that limit infiltration. Biological processes than can cause clogging are the accumulation of algae on the infiltration surface and micro-organism growth within the sand bed due to incoming biomass. These process block or reduce pore size, improving effluent water quality while requiring more head to drive the water through. Chemical processes such as chemical precipitation, vapor barriers caused by the trapping of gasses produced by bacteria and air binding can reduce infiltration rates as well. Since it is not possible to backwash the filtering sand layer the sand layer must be replaced periodically in order to maintain proper inflow rates into the recharge pit. When infiltration rate though the filtering layer becomes greater than infiltration rate into the soil it becomes the limiting factor in the recharge rate of the pit. This cause the pit to lose effectiveness over time and can cause problems due to concentrating runoff around the pit location or creating areas of standing, stagnate water over the pit.

  Water table depth is also an important factor in recharge pit design. Shallow aquifers are preferred as the infiltration rate is much more responsive to water table depths in these cases and residence time within the water table is reduced, allowing for the more immediate use of the captured water. Small differences in water level of the recharge pit and water table depth also cause groundwater flow away from the pit to be lateral, making use of the large surface area of the unlined sides of the pit rather than the pit bottom alone. Shallow aquifers also avoid “perched mounding” where the infiltrated water reaches a layer of reduced permeability and head must build on the layer before the water can penetrated it and reach the well aquifer. It is also important to insure that the wet season water table does not rise above the pit bottom which can, with the additional recharge created by the pit, cause the soil to become waterlogged. This limits infiltration in the surrounding area prolonging the period where the top layer of soil is saturated and water cannot infiltrate. This prolonged period of topsoil saturation increases risk of flooding and erosion, causing additional runoff and standing water.

Artificial Recharge Movement in India

  Artificial groundwater recharge has been historically common in India and continues today. Many communities in arid regions have managed recharge pits or like structures for many years. Without government intervention or scientific knowledge base residents used knowledge of the land and local climate to store water in locations necessary. As problems with over pumping and the subsequent effects became clearer, government and scientific bodies soon began an effort to promote healthy groundwater management. National and non-governmental bodies began to put I place pilot programs to and studies to assess groundwater conditions and solutions to existing problems. This involved a number of techniques, including recharge pits and trenches. The study of artificial recharge and application to development projects was a main strategy for India in managing its water supply. These resulted in the development and release of technical guidelines in the area which caused the practice to become more common.

   Now that water scarcity is an undeniable issue in the country India and other nations have placed a renewed importance on artificial recharge. The synthesis of local, regional and national effort to further develop and implement simple and easily manageable recharge systems and practices has largely benefited dry areas. In some cases nation orders have mandated rainwater harvesting and artificial recharge. This has created a transition from transporting water from remote reservoirs to the local and individual management of immediately available water sources giving the artificial recharge movement momentum to continue to grow and propagate through nearby locations.

   The Mazhapolima Participatory Well Recharge Programme is a well suited example of this phenomenon. Local government, the Thrissur District Administration, along with NGOs, private sector sponsors and individual households has developed a network of water providers and users to coordinate in an effort to maintain suitable groundwater conditions and improved access to drinking water. To achieve this, the program pans to recharge groundwater and improve water availability and service level in order to reduce drought impact, improve public health and increase agricultural productivity.

   By creating a community based, participatory program the MPWRP relies on decentralized solutions, such as recharge pits and withdrawal wells, to solve existing problems. The water demand motivates individuals and groups to make small investments in order to take advantage of the meaningful benefits of clean, reliable water. This approach is seen as the most cost effective as many of the maintenance and initial cost is not supplied by the program, but the community members themselves. The program promotes and assists in determining feasible solutions and circulating information on the subject. Eventually the program hopes to be able to recharge 4.5 million open wells in the affected area.

Conclusion

   Recharge pits are an extremely cost effective approach with a design based on the reliance of naturally occurring processed. This make solutions like recharge pits and trenches suitable for developing regions with limited capital and infrastructure. The low footprint and unobtrusive nature of these technologies make it suitable for more developed, urban regions as well. By improving the groundwater health of a location artificial recharge has a domino effect on the health of the environment and community. This simple technology that has been practiced for many years is now more applicable than ever in solving many of our water problems.

References
 

Bouwer, Herman (02/28/2002). "Artificial recharge of groundwater: hydrogeology and engineering". Hydrogeology journal (1431-2174), 10 (1), p. 121.

Ruffino, L. Water Conservation Technical Briefs. SAI Platform, 2009. Web. 17 Nov. 2011. <http://www.saiplatform.org/uploads/Library/>.

Sakthivadivel, Ramaswamy. The Groundwater Recharge Movement in India. Sri Lanka: IWMI, Digital file.

Thrissur District Government of Kerala. "Participatory Well Recharge Program." Mazhapolima Project Report. June 2008. Web. 17 Nov. 2011. <http://www.indiawaterportal.org/sites/indiawaterportal.org/>.

A Look at the Water and Sanitation Situation in Vietnam

 Vietnam, officially the Socialist Republic of Vietnam, is a developing county located on the Indochina Peninsula. The 13th most populated country in the world; it has made substantial strides toward Millennium Development Goal, or MDG, target 7c. A summary of statistical data on Vietnam can be seen in table 1.

 MDG target  7c aims at ensuring environmental sustainability, specifically halving the proportion of the population without improved drinking water and basic sanitation by 2015. Improved drinking water is defined by the type of technology and level of service more likely to provide safe drinking water. Sources include in domestic connections, public standpipes, protected wells and springs, and rainwater collection. Unimproved sources would include unprotected wells and springs as well as vendor and tanker truck provided water. To ensure sustainability the withdrawal should not exceed what is available which includes sound supply and management practices.

 Currently access to improved water sources and sanitation in Vietnam is fairly good and the MDG has already been reached. Currently 94% of the population has access to improved water sources and 75% has access to basic sanitation. Compared to 58% and 35% respectively in 1990, both sectors currently comply with the MDG. The largest improvements have been in in rural areas though this may be due to both urban migration and the large margin for improvement. This is not to overshadow urban progress as it has been substantial as well. These figures as well as others can be seen in table 2. The progress of improvement from 1990 to 2008 can also be seen in the drinking water ladder, figure 1.

Vietnam
Location	Southeast Asia
Bordering Nations	China, Laos, and Cambodia
Area	310,070 sq mi
Population
Population	90.55 million
Population Growth Rate	1.077
Urban Population	30.00%
Infant Mortality Rate	20.9 deaths / 1000 live births
Life Expectancy	72.2 yrs
Total Fertility Rate	1.91 children per woman
Literacy Rate	94.00%
Economy
GDP (PPP)	$276.6 billion
GDP Ranking	42
GDP by Sector
Agriculture	20.6%
Industry	41.1%
Services	38.3%
Labor Force by Sector
Agriculture	53.9%
Industry	20.3%
Services	25.8%
Unemployment Rate	4.4%
Population Below Poverty Line	10.60%
Table 1. Country Profile
Water and Sanitation
Renewable Water Resources	891.2 cu km
Freshwater Withdrawl	71.39 cu km
Freshwater Withdrawl per Capita	847 cu m
Freshwater Usage
Domestic	8.0%
Industry	24.0%
Agricultre	68.0%
Improved Drinking Water 2008
Urban	99.0%
Rural	92.0%
Total	94.0%
Improved Drinking Water 1990
Urban	88.00%
Rural	51.00%
Total	58.00%
Improved Sanitation 2008
Urban	94.0%
Rural	67.0%
Total	75.0%
Improved Sanitation 1990
Urban	61.0%
Rural	29.0%
Total	35.0%
Table 2. Water and Sanitation Data



Figure 1. Vietnam Water & Sanitation Ladder

Documentery Review: "Blue Gold: World Water Wars"

 Sam Bozzo's documentary "Blue Gold: World Water Wars," adapted from the book "Blue Gold: The Right to Stop Corporate Theft of The Worlds Water," is a look into the world of water, how it is used, and who controls it. The imbalances in the water cycle that modern societies have created, and many of the solutions proposed, may be setting a scene for a socially unsustainable system in dealing with, what may believe to be, a basic human right.

 To understand problems with water management the first issue that the film addresses is their cause. We all know that fresh water composes a slim percentage of the worlds water source, around 2.5%, and that much of this is quickly, if not already, becoming polluted beyond human use. When this happens surface waters become an unsuitable source, and in response much of the worlds fresh water supply has become dependent on ground water. While in some situations this is a perfectly suitable solution, the levels of groundwater that we, as a human race, are using is outpacing the recharge rates of many of our aquifers. The urbanization of much of the world is working to further hider the ability of these aquifers to recharge and, with population becoming concentrated in the very areas we are draining, this necessitates the import of water to the points of demand. This upsets local water cycles and is resulting in the desertification of many of the earths landscapes, which creates a whole other set of problems. Massive sinkholes are popping up in many major cities where groundwater is heavily relied upon and, in areas where water is exported, the landscape is quickly deteriorating. To truly solve the problem we must eliminate the cause and learn, as a society, to adapt to our water resources rather than adapt these resources to ourselves.

 In an effort to maintain current development and water use practices water is being imported, not only as liquid water but imbedded water, to areas of demand. Imbedded water is the water both contained in goods and associated with the production of them. This documentary takes an in depth look at this phenomenon through bottled water, perhaps the most obvious example of our irrational view of this resource. Not only does bottled water transport liquid water far from the source, but it takes 1.85 gallons of fresh water to manufacture the very bottle that it is contained in. Once that water has left the source it is rarely replaced. The same principal can be applied to food and other products where the water burden is bared by the developing world at almost no cost to the consumer. This constitutes a paradox in many markets where water use is profited upon but the negative effects on water resources are an overlooked externality.

  The privatization of water resources is another issue heavily criticized by the film. As the title "Blue Gold" implies water is seen by many as the new oil and corporations are scrambling to secure as much of it as possible. Typically, this involves poaching the developing worlds water supplies, applying highly technical solutions to areas were much of the population cannot support the cost. This means that if people cannot afford the water, they go thirsty. If your house catches on fire, you have to pay to put it out. If you have no source of income you have to rely on the same surface water that many of the same companies pollute. The public heath cost of having little water or that of poor quality falls on the government while the profits form the provision of clean water go to large, international corporations. Many governments see these deals as attractive, as they provide short term incentives in the form of initial purchase of water rights and often individual benefits for those involved in the deal making, but the long term consequences limit development and standards of living.

 Much as in the previously reviewed "The Big Thirst," "Blue Gold" shows that there needs to be a change in the way the world looks at water and how it is used. Many of the environmental problems of today stem from this issue and their solutions are highly dependent on how we solve it. In order to create a sustainable future we first need to create sustainable systems of use for our most basic resources, water being principal among them. Are we willing to allow water to become increasingly involved in the same system that has created so many of the other problems we are facing today? We should all take a good look at what is happening in this issue and what the outcomes are likely to be.

Book Review: Charles Fishman's "The Big Thirst"

 This year's hot new book about water, "The Big Thirst" written by Charles Fishman, has brought to the public eye what many who are involved in the business and study of water, water resources and water management have long known. Water resource problems are a fact and, if we continue with business as usual, are coming to a town near you. Throughout the world, water crises are popping up, too much water here or too little there. But why are these incidents so shocking? The reliability of water systems in the western world is so ingrained to our consciousness we hardly question it. We, as a society, place little value on our most precious resource, confident that it will be there when we need it. And this is simply not the case.

  Fishman uses this book to examine how and why we use water the way we do while taking account of what is going right and what is going wrong. The book is filled with case studies, from the United States, to Australia, to India looking at domestic, agricultural, and industrial situations to provide a "big picture" view of the situation and where it is heading. The common thread to all of these cases is the value we place on water. Typically this value is trivial, water is cheap, easily accessible, and taken for granted by many. It comes from an unkown source through unknown means and the waster water is taken care of in an unknown manner. To much of the population it is simply a black box.

  All of this is changing though. Water prices are rising, sources are becoming less dependable and, with the recent attention being brought to emerging contaminants, quality is being questioned. The view of water as a resource and the effort to effectively manage it as such is a change that needs to take place in society, from top industries to single family homes. Water reuse, conservation, and protection are all practices that can both lead to and result from these changes and are a few of the things that must be done in order to deal with water scarcity problems around the world. Big businesses such as IBM and Coca-Cola realize this and are taking measures to achieve levels of water management previously unseen. And they are not doing this out of ethical responsibility either, they are doing it because it makes sense. The economic benefits to these companies, who use massive amounts of water for their operations are clear. The money saved from pumping, cleaning, and then disposing of this natural resource are substantial, and as domestic prices rise will matter to everyday people as well. The effort to protect natural water and use less is not an environmental movement, it is an economic one.

 The take-away message of the book is short and sweet, the "golden-age" of water is over and the sooner we acknowledge this and adapt, the better off we will be.

Statement of Purpose

 Hello to all you water lovers. My name is Jacob Mueller and over the past year I have become intensely interested in water and sanitation in the developing world and the decentralized solutions to these problems. The more information I uncover, the more I feel that these types of solutions are essential to improved water availability, water quality and overall health worldwide. I am currently studying environmental engineering at N.C. State University and have begun to focus on the subject. I recently completed my senior design project on latrine design and  am presently enrolled in a class about the issue specifically.

 In order to further my knowledge of the subject, as well as develop a view of the most current trends in the area, I have created this blog as an outlet of information and record of what I discover. I will include book reviews, information from industry and business leaders, case studies on related projects, and anything else I can unearth. Through this I hope to create a comprehensive view of the overall water situation with a special focus on non-traditional and developing world approaches. When all is said and done I, as well as anybody else who follows, should be fully knowledgeable and competent on the subject.

 So read, learn and enjoy. I look forward to meeting all who share my intrest in tackling these problems and working to make the world a better place. Talk to you soon.

- Jake