The First Solar Plant In Kenya That Turns Ocean Water Into Drinkable Water

Around 2.2 billion people in the world don’t have access to drinking water services that are managed safely. This happens on a planet that is 71% covered by that essential element for life. What seems like a contradiction, may actually be the key challenge for the future of humanity: How can we turn the seawater of the oceans into drinking water. The answer seems to be located in a small town in Kenya, near the border of Somalia.

According to W.H.O and a report published by UNICEF, one in every three people lack access to clean drinkable water, and the situation is even worse in Africa. This is the reason the GivePower NGO chose the small village of Kenya, Kiunga, to turn Indian Ocean’s salty water into drinkable ‘sweet’ water. This project has been operating since last year and it looks promising.

A typical desalination plant consumes high amounts of power, the process is expensive, and it can only operate in areas that have enough facilities to produce and distribute that much energy. The NGO solved these problems by using a technology they call “solar water farms,” which involve the installation of solar panels that are able to produce 50 kilowatts of energy, high-performance Tesla batteries to store it, and 2 water pumps that operate 24 hours a day.

The system can generate drinking water for 35,000 people every day. Besides, according to GivePower, the water quality is better than that of a typical desalination plant. Plus it doesn’t even have the negative environmental impact that the process usually causes since the extraction of salt produces saline residues and pollutants that are harmful to animals and plants.

What this solution differs from the regular desalination plant is that is much more efficient, and it uses a technology known as “solar water farms,” which involves the installation of solar panels that can produce 50 kilowatts of energy, high-performance Tesla batteries to store it, and two water pumps which operate 24 hours per day.

Two Students Engineer Bacterium That Can Transform Plastic Into Carbon dioxide And Water In 24 Hours

The bacterium has been developed by two students, Jeanny Yao and Miranda Wang. The duo has been working on bacterium since their school years and is now getting ready to reap the benefits from it. The duo has already procured all patents and even managed to secure a funding of four hundred thousand dollars to develop a product at the age of twenty years.

Thanks to the bacterium, they both have already won five prizes and become quite popular because they are the youngest ever to win the Perlman science prize. All of this has been made possible because of this small bacteria that can transform plastic into CO2 and water. The technology can be used for two purposes; cleaning the beaches and creating raw materials for clothing.

Miranda Wang said, ‘It is practically impossible to make people stop using plastic, we need technology to break the material, and everything becomes biodegradable.’ The development of bacterium has been comprised of two parts. The first part is where the plastic is dissolved, and the enzymes catalyze, thus making the plastic become highly malleable fractions. These components are then housed in a biodigester station where they act as if they are leftovers of food. The project has to run for only 24 hours during which it transforms plastic to water.
https://wonderfulengineering.com

Coal fired power plants

Coal fired power plants are a type of power plant that make use of the combustion of coal in order to generate electricity. Their use provides around 40% of the world's electricity and they are primarily used in developing countries. Countries such as South Africa use coal for 94% of their electricity and China and India use coal for 70-75% of their electricity needs, however the amount of coal China uses dwarfs most other countries (see the data visualization below). The use of coal provides access to electricity to those who previously didn't have it, which helps to increase quality of life and reduce poverty in those regions, however it produces large quantities of different pollutants which reduces air quality and contributes to climate change.

Burning huge amounts of coal

Coal plants require enormous amounts of coal. Shockingly: a 1000 MWe coal plant uses 9000 tonnes of coal per day, equivalent to an entire train load (90 cars with 100 tonnes in each!). The amount of coal used during a full year would then require 365 trains, and if each is 3 km long then a single train carrying all of this coal would need to be about 1100 km long; about the same distance as driving from Calgary AB to Victoria BC. If this train were to pass by your house at 40 kilometers per hour, it would take more than a day to pass!

 

 The conversion of this coal to the end goal of electricity is a multi-faceted process:

1. The coal must be unloaded from the train. Traditional ways of doing this require the use of cranes picking up the coal from the cars, however newer plants have the floor underneath the train tracks drop away, allowing the coal to be dropped into underground containment. Doing so doesn't even require the train to stop moving! . Many coal plants are mine mouth which means the plant was put where the coal mine is, so the coal doesn't need to be transported by train.
2. Once unloaded, the coal is then pulverized into a fine powder by a large grinder. This ensures nearly complete burning of the coal in order to maximize the heat given off and to minimize pollutants.
3. The pulverized coal is then input to a boiler, where combustion occurs and the coal provides heat to the power plant. This heat is transferred to pipes containing high pressured water, which boils to steam.
4. The steam then travels through a turbine, causing it to rotate extremely fast which in turn spins a generator, producing electricity. The electricity can then be input to the electrical grid for use by society.

Coal fired power plants follow the Rankine cycle in order to complete this process. Since they require plenty of water to be circulated in this cycle, coal power plants need to be located near a body of water. The process of coal fired plants can be seen below in Figure 

Erin Brockovich (Ground WATER Pollution)

In 1993, Erin Brockovich (Julia Roberts) is an unemployed single mother of three children, who has recently been injured in a traffic accident with a doctor and is suing him. Her lawyer, Ed Masry (Albert Finney), expects to win, but Erin's explosive courtroom behavior under cross-examination loses her the case, and Ed will not return her phone calls afterwards. One day he arrives at work to find her in the office, apparently working. She says that he told her things would work out and they didn't, and that she needed a job. He feels bad for her, and decides to give her a try at the office.

Erin is given files for a real-estate case where Pacific Gas and Electric (PG&E) is offering to purchase the home of Hinkley, California, resident Donna Jensen. Erin is surprised to see medical records in the file and visits Donna, who explains that she had simply kept all her PG&E correspondence together. Donna appreciates PG&E's help: she has had several tumors and her husband has Hodgkin's disease, but PG&E has always supplied a doctor at their own expense. Erin asks why they would do that, and Donna replies, "because of the chromium". Erin begins digging into the case and finds evidence that the groundwater in Hinkley is seriously contaminated with carcinogenic hexavalent chromium, but PG&E has been telling Hinkley residents that they use a safer form of chromium. After several days away from the office doing this research, she is fired by Ed until he realizes that she was working all the time, and sees what she has found out.

Rehired, she continues her research, and over time, visits many Hinkley residents and wins their trust. She finds many cases of tumors and other medical problems in Hinkley. Everyone has been treated by PG&E's doctors and thinks the cluster of cases is just a coincidence, unrelated to the "safe" chromium. The Jensens' claim for compensation grows into a major class-action lawsuit, but the direct evidence only relates to PG&E's Hinkley plant, not to the senior management.

Knowing that PG&E could delay any settlement for years through delays and appeals, Ed takes the opportunity to arrange for disposition by binding arbitration, but a large majority of the plaintiffs must agree to this. Erin returns to Hinkley and persuades all 634 plaintiffs to go along. While she is there, a man approaches her to say that he and his cousin were PG&E employees, but his cousin recently died from the poison. The man says he was tasked with destroying documents at PG&E, but, "as it turns out, I wasn't a very good employee".

He gives Erin the documents: a 1966 memo proves corporate headquarters knew the water was contaminated with hexavalent chromium, did nothing about it, and advised the Hinkley operation to keep this secret. The judge orders PG&E to pay a settlement amount of $333 million to be distributed among the plaintiffs.

In the final scene, Ed hands Erin her bonus payment for the case but warns her he has changed the amount. She explodes into a complaint that she deserves more respect, but is astonished to find that he has increased it—to $2 million.

Life cycle assessment

Definition
The International Standards Organization (ISO) has defined LCA as :
"A technique for assessing the environmental aspects and potential impacts associated with a product by:
· Compiling an inventory of relevant inputs and outputs of a product system,
· Evaluating the potential environmental impacts associated with those inputs and outputs,
· Interpreting the results of the inventory analysis and impact assessment phases in relation to the objectives of the study" (ISO 14.040).

The technique examines every stage of the life cycle, from the winning of the raw materials, through manufacture, distribution, use, possible re-use/recycling and then final disposal.

For each stage, the inputs (in terms of raw materials and energy) and outputs (in terms of emissions to air, water, soil, and solid waste) are calculated, and these are aggregated over the Life Cycle.
These inputs and outputs are then converted into their effects on the environment, i.e. their environmental impacts.
The sum of these environmental impacts then represents the overall environmental effect of the Life Cycle of the product or service.

LCA Background
The concept of life-cycle assessment first emerged in the late 1960's but did not receive much attention until the mid-11980's
In 1989, the Society of Environmental Toxicology and Chemistry (SETAC) became the first international organization to begin oversight of the advancement of LCA.
In 1994, the International Standards Organization (ISO) began developing standards for the LCA as part of its 14000 series standards on environmental management. The standards address both the technical details and conceptual organization of LCA .
• ISO 14040-A standard on principles and framework
• ISO 14041-A standard on goal and scope definition and inventory analysis
• ISO 14042-A standard on life-cycle impact assessment
• ISO 14043-A standard on life-cycle interpretation

Several of the methods described as LCA methods follow the LCA framework defined in ISO 14040, involving an inventory similar to that described in ISO 14041, and assessment of impacts to some degree as described in ISO 14042, while a smaller number take on the normalization and weighting also discussed in ISO 14042.

Still, methods based on the ISO standards may differ greatly, given that the ISO standards allow flexibility to customize characterization and normalization factors and weighting methods to suit the values and conditions of a particular location or sector.

Goal And Scope
This is the first stage of the study and probably the most important, since the elements defined here, such as purpose, scope, and main hypothesis considered are the key of the study.

The scope of the study usually implies defining the system, its boundaries (conceptual, geographical and temporal), the quality of the data used, the main hypothesis and a priori limitations.
A key issue in the scope is the definition of the functional unit.
This is the unit of the product or service whose environmental impacts will be assessed or compared.
It is often expressed in terms of amount of product, but should really be related to the amount of product needed to perform a given function.

During the goal definition process, the following issues should be considered:

• Why is the study being conducted (i.e., what decision, action, or activity will it contribute to or affect)?
• Why is LCA needed for this decision, action, or activity? What, specifically, is it expected to contribute?
• What additional analytical tools are needed and what will they be expected to contribute?
• Who is the primary target audience for the study (i.e., who will be making the decision, taking or directing the action, or organizing or participating in the activity)?
• What other audiences will have access to the study results? What uses might these audiences make of the study findings?
• What are the overall environmental goals, values, and principles of the sponsoring organization and intended audience?
• How does the intended application of the study relate to these goals, values, and principles?

System Boundaries

Definition of system boundaries
The scope of an LCA describes the boundaries which define the system being studied.
The scope should be well defined to ensure that the breadth and depth of the study are compatible with the stated goal.
For example, in a comparison of virgin and recycled systems, removal of downstream stages may not affect comparative rankings significantly.
However, if objectives go beyond comparative rankings to assessing environmental burdens throughout the life cycle, eliminating the downstream stages may exclude some environmental impacts that are unique to recycled systems and that have comparatively high burdens in the downstream stages.

System boundaries define the unit processes or activities that will be included in the system under study. Decisions must be made on which processes or activities will be included.

As noted above under consideration of the functional unit, it might be possible to eliminate those processes that are identical for all items under study.
Or, it might be possible to eliminate elements of the system that are beyond the purview of the study goal and purpose, i.e., those components of the system that cannot be affected by the decisions, actions, or activities that are driving the study.

The basis for the decisions should be clearly understood and described and should be consistent with the stated goal of the study. At the outset of an LCA, all life-cycle stages should be considered.

Upon careful review, it may be possible to eliminate the need to collect data from some of these stages or sub processes.
The study team should keep in mind, however, that Barnthouse et al. (1997) noted several features that are crucial to LCA

• a system-wide perspective embodied in the term "cradle-to-grave" that implies efforts to assess the multiple
• operations and activities involved in providing a product or services;
• a multimedia perspective that suggests that the system include resource inputs as well as wastes and emissions to all environmental media, i.e., air, water, and land; and
• a functional unit accounting system that normalizes energy, materials, emissions, and wastes across the system and media to the service or product provided.

Any decisions that affect these features should be carefully documented.

A true life-cycle always starts with the extraction of the raw materials from the earth and ends with the final disposal of the refusals in the earth.
In practice every system can be described, but if the described system do not satisfy the condition illustrated above, it does not represent an LCA but an eco-balance or an eco-profile.

Kirk et al., 2005, have pointed out the influence of system boundaries on LCA results, since setting system boundaries in different ways can tip the scales in favor of one technology over another.

They showed how the concepts of system boundaries and parameters help illuminate why wastewater decisions may only move problems in time and space, rather than solve them.

System Function And Functional Unit
The functional unit is a measure of the performance of the product system. The primary purpose of the functional unit is to provide a reference to which the inputs and outputs are related and is necessary to ensure comparability of results.

The function is related directly to the questions that the study is designed to answer, and the functional unit must be selected as the basis for the study.

One of the primary purposes for a functional unit is to provide a reference for the system inputs and outputs.
A well-defined functional unit that assures equivalence also allows for more meaningful comparisons between alternative systems.
In their study of Life cycle assessment of wastewater treatment technologies treating petroleum process waters, Vlaopolous et al. 2006 have considered a process water flow of 10,000 m3/day for a time period of 15 years (system design life) as the function unit used in order to compare the different wastewater treatment processes.

Inventory Analysis
The inventory analysis is a technical process of collecting data, in order to quantify the inputs and outputs of the system, as defined in the scope.
Energy and raw materials consumed, emissions to air, water, soil, and solid waste produced by the system are calculated for the entire life cycle of the product or service.

In order to make this analysis easier, the system under study is split up in several subsystems or processes and the data obtained is grouped in different categories in a LCI table.

Impact Assessment
Life Cycle Impact Assessment (LCIA) is a process to identify and characterize the potential effects produced in the environment by the system under study.

The starting point for LCIA is the information obtained in the inventory stage, so the quality of the data obtained is a key issue for this assessment.
LCIA is considered to consist of four steps that are briefly described below.

The first step is Classification, in which the data originated in the inventory analysis are grouped in different categories, according to the environmental impacts they are expected to contribute.

Indicators of impact categories include:
Climate change
Acidification
Eutrophication
Photochemical smog
Fossil fuel depletion
Ecotoxicity
Ozone depletion
Human toxicity

The second step, called Characterization, consists of weighting the different substances contributing to the same environmental impact.
Thus, for every impact category included in LCIA, an aggregated result is obtained, in a given unit of measure.

The third step is Normalization, which involves relating the characterized data to a broader data set or situation, for example, relating SOx emissions to a country's total SOx emissions.

The last step is weighting, where the results for the different impact categories are converted into scores, by using numerical factors based on values.

This is the most subjective stage of an LCA and is based on value judgments and is not scientific.
For instance, a panel of experts or public could be formed to weight the impact categories.
The advantage of this stage is that different criteria (impact categories) are converted to a numerical score of environmental impact, thus making it easier to make decisions.

Interpretation
This is the last stage of the LCA, where the results obtained are presented in a synthetic way, presenting the critical sources of impact and the options to reduce these impacts.
Interpretation involves a review of all the stages in the LCA process, in order to check the consistency of the assumptions and the data quality, in relation to the goal and scope of the study.

Elements of the Study Design
The study designers and sponsors consider numerous elements of the study design.
The following questions are considered during this process.

• Depth and detail
• -What level of depth and detail of data does the application require?
• -Are these requirements greater for some data categories and issues than for others?
• Breadth and completeness
• - Does the application require that all aspects of the life cycle be included, or can some be eliminated or examined less exhaustively?
• - What inventory and impact-category indicators must be included to meet the purpose of the study?
• - Where are the systems boundaries drawn and why?
• Transparency
• - What degree of openness and comprehensiveness is required in the presentation of data or study results?
• - Who will see the products of the study, including underlying data as well as results, and how much transparency will they require?
• - Will proprietary data be used that must be shielded from some users?
• Data sources
• - Where are the data to be collected?
• - Are publicly available data sources appropriate for the study?
• -Are primary data required?
• - Is a mix of approaches appropriate for the study?
• Data quality
• -How much confidence should the potential users have in the data and in the study's conclusions?
• - How much uncertainty can they tolerate?
• Modeling allocation conventions
• -How is recycling to be treated?
• -How are burdens of a process to be allocated among co-products?
• Site specificity
• -Does the application require that the study produce information about specific sites or facilities?
• -Is site-specific information needed for any of the planned supplemental analyses, such as risk assessment?
• Scale
• -Does the application require data on a global, continental, regional, and local scale?
• - Which biological scales are most relevant-ecosystems, populations, individual organisms, physiological systems, or molecular systems?
• -Are users of the study interested only, or primarily, in impacts that occur at a particular scale?
• Level of aggregation
• -What level and types of aggregation are most appropriate to support the study decision needs?
• - Will the traditional LCA approach of aggregating all data throughout the life cycle by functional unit be sufficient, or will the user require some data to be retrievable in a disaggregated form (e.g., by industrial process)?
• LCA limitations
• -How environmentally relevant is the modeling that was used in the impact assessment?
• - Does the intended application require more precise modeling of risk or hazard?
• Temporal specificity
• -Does the application require that the study produce information on the time frame for when potential impacts or their associated inventory items occurred?

Benefits and limitations of the life cycle approach
Life Cycle Assessment is an inclusive tool.
All necessary inputs and emissions in many stages and operations of the life cycle are considered to be within the system boundaries. This includes not only inputs and emissions for production, distribution, use and disposal, but also indirect inputs and emissions - such as from the initial production of the energy used - regardless of when or where they occur.

If real environmental improvements are to be made by changes in the product or service, it is important not to cause greater environmental deteriorations at another time or place in the Life Cycle.

LCA offers the prospect of mapping the energy and material flows as well as the resources, solid wastes, and emissions of the total system, i.e. it provides a "system map" that sets the stage for a holistic approach.

The power of LCA is that it expands the debate on environmental concerns beyond a single issue, and attempts to address a broad range of environmental issues, by using a quantitative methodology, thus providing an objective basis for decision making.

Unfortunately, LCA is not able to assess the actual environmental effects of the system.
ISO 14.042 standard, dealing with Life Cycle Impact Assessment, specially cautions that LCA does not predict actual impacts or assess safety, risks, or whether thresholds are exceeded.

The actual environmental effects of emissions will depend on when, where and how they are released into the environment, and other assessment tools must be utilized.

For example, an aggregated emission released in one event from one source, will have a very different effect than releasing it continuously over years from many diffuse sources.

Clearly no single tool can do everything, so a combination of complementary tools is needed for overall environmental management.

LCA in waste management
LCA has begun to be used to evaluate a city or region's future waste management options.
The LCA, or environmental assessment, covers the environmental and resource impacts of alternative disposal processes, as well as those other processes which are affected by disposal strategies such as different types of collection schemes for recyclables, changed transport patterns and so on.

The complexity of the task, and the number of assumptions which must be made, is shown by the simplified diagram (above) showing some of the different routes which waste might take, and some of the environmental impacts incurred along the way.
Those shown are far from exhaustive.

References

Azapagic, A., (1999). Life cycle assessment and its implications to process selection, design and optimization, Chemical Engineering Journal, 3, 73, pp1-21.

Barnthouse L, Fava J, Humphreys K, Hunt R, Laibson L, Noesen S, Owens JW, Todd JA, Vigon B, Weitz K, Young J, editors. 1997. Life-cycle impact assessment: the state-of-the-art. Pensacola FL: Society of Environmental Toxicology and Chemistry

(SETAC).

Fava J, Jensen A.A., Lindfors L., Pomper S., De Smet B., Warren J., Vigon B., eds. (1994)

SETAC, Life-cycle assessment data quality: a conceptual framework Workshop report,

Wintergreen, OOctober 1992. Pensacola: SETAC.

Huppes, G., Francois, S., (eds) (1994). Proceedings of the European Workshop on allocation in LCA, 24-25 FFebruary1994, Leiden, the Netherlands, SETAC- Europe, BBrussels Belgium

Kirk, B., Etnier, C., Kärrman, E., and Johnstone, S. (2005), Methods for Comparison of Wastewater Treatment Options. Project No. WU-HT-03-33. Prepared for the National Decentralized Water Resources Capacity Development Project. Washington University, St. Louis, MO, by Ocean Arks International, Burlington, VT.

Miettinen, P. and Hamalainen, R., (1997). How to benefit from decision analysis in environmental life ccycleassessment "European Journal of Operational Research. Vol 102,2, pp279-294

Udo de Haes, H., (1994). Guidelines for the application of life - cycle assessment in the European Union ecolabelling programme SPOLD, Brussels, Belgium.

Vlasopoulos, N.,Memon, F.,Butler, Murphy, R., (2006), Life Cycle Assessment of Wastewater Treatment Technologies, Treating Petroleum Process Waters. Sci.Total Environm.,(367), 58-70.

Introductory reading:

1. From the LCAccess website (U.S. EPA), http://www.epa.gov/ORD/NRMRL/lcaccess/

Read the "Why LCA?" section. Other browsing is optional.

2. "How is a Life Cycle Assessment Made?" pp. 11-24 in Life Cycle Assessment: What it is and how to do it; UNEP, 1996.

3. Masters, GM (1998): Introduction to Environmental Engineering and Science (2nd

edition); extract from ch. 9 "An example of life cycle assessment: Polystyrene cups",

p562-565.

Further LCA Resources

1. Books

Ciambrone, DF, Environmental Life Cycle Analysis, Lewis Publishers, 1997

Curran, MA, Environmental Life Cycle Assessment, McGraw-Hill, 1996

Graedel, TE, Streamlined Life-Cycle Assessment, Prentice Hall, 1998

Vigon, BW et.al., Life-Cycle Assessment: Inventory Guidelines and Principles, USEPA Risk

Reduction, Lewis Publishers, 1994

Weidema, BP (ed.), Environmental Assessment of Products: a Handbook on Life Cycle Assessment,

2nd edition, UETP-EEE, Finnish Association of Graduate Engineers, Helsinki, 1993

2. Journal Articles and ISO Standard

ISO 14040 series of standards: SABS ISO 14040 (1998), SABS ISO 14041 (1999), ISO 14042 (1999),

ISO 14043 (2000) and ISO14044. Some Case Studies:

_ Vollebregt, LHM and J Terwoert, LCA of Cleaning and Degreasing Agents in the Metal Industry, Int. J. of LCA, 3 (1), 12-17, 1998.

_ Andersson, K and T Ohlsson, Life Cycle Assessment of Bread Produced on Different Scales, Int. J. of LCA, 4 (1), 25-40, 1999.

3. LCA Websites

UNEP/SETAC Life Cycle Initiative: http://www.uneptie.org/pc/sustain/lcinitiative/

U.S. EPA, NRMRL: LCAccess: http://www.epa.gov/ORD/NRMRL/lcaccess/

CML - Centre for Environmental Science: http://www.leidenuniv.nl/interfac/cml/

SETAC Foundation for Environmental Education: http://www.setac.org/lca.html

Pre Product Ecology Consultants: http://www.pre.nl/

Ecobilan (Software Developers and Consultants): http://www.ecobilan.com

The International Journal of LCA: http://www.ecomed.de/journals/lca/

4. Software Tools and Data Libraries

CML LCA - free LCA software

Commercial software: SimaPro, GABI, Umberto

EcoInvent database represents the state of the art - at cost

BUWAL, IVAM, USA I/O, US database project, ETH - some free, some not

Danish food and agriculture database - freesment, McGraw-Hill, 1996

Graedel, TE, Streamlined Life-Cycle Assessment, Prentice Hall, 1998

Vigon, BW et.al., Life-Cycle Assessment: Inventory Guidelines and Principles, USEPA Risk

Reduction, Lewis Publishers, 1994

Weidema, BP (ed.), Environmental Assessment of Products: a Handbook on Life Cycle Assessment,

2nd edition, UETP-EEE, Finnish Association of Graduate Engineers, Helsinki, 1993
http://grimstad.uia.no/puls/climatechange/nns05/13nns05a.htm

Urban Rainwater Harvesting

Introduction

Rainwater harvesting (RWH) is a simple technique that offers many benefits. It can be done very low-tech, doesn’t cost much and is applicable at small-scale with a minimum of specific expertise or knowledge; or in more sophisticated systems at large-scale (e.g. a whole housing area).The most common technique in urban areas (besides storm water management) is rooftop rainwater harvesting: rainwater is collected on the roof and transported with gutters to a storage reservoir, where it provides water at the point of consumption or is used for groundwater recharge (see also surface and subsurface artificial groundwater recharge). Collected rainwater can supplement other water sources when they become scarce or are of low quality like brackish groundwater or polluted surface water in the rainy season. It also provides a good alternative and replacement in times of drought or when the water table drops and wells go dry. The technology is flexible and adaptable to a very wide variety of conditions. It is used in the richest and the poorest societies, as well as in the wettest and the driest regions on our planet (HATUM & WORM 2006).

Basic Design Principles

Rooftop rainwater harvesting system.Source: CPREEC (Editor) (n.y.)

Each rainwater harvesting system consists of at least the following components (INFONET-BIOVISION 2010):

1. Rainfall


2. A catchment area or roof surface to collect rainwater.


3. Delivery systems (gutters) to transport the water from the roof or collection surface to the storage reservoir.


4. Storage reservoirs or tanks to store the water until it is used.


5. An extraction device (depending on the location of the tank - may be a tap, rope and bucket, or a pump (HATUM & WORM 2006); or a infiltration device in the case the collected water is used for well or groundwater recharge (see also surface or subsurface artificial groundwater recharge)

Additionally there are a wide variety of systems available for treating water either before, during and/or after storage (e.g. biosand filter, SODIS, chlorination; or in general HWTS).

Process diagram of a drinking water RWH system.Source: THOMAS & MARTINSON (2007)

Illustration of water flow scheme of a RTRWH system. Basic components: roof, gutters, first flush device (first rain separator), rain barrel with filter and tap and recharge well. Source: RAINWATERCLUB (Editor) (n.y.)

Rainfall

Table 1: Average Annual Rainfall in different regions. Source: HATUM & WORM (2006)

The rainfall pattern over the year plays a key role in determining whether RWH can compete with other water supply systems. Tropical climates with short (one to four month) dry seasons and multiple high-intensity rainstorms provide the most suitable conditions for water harvesting. In addition, rainwater harvesting may also be valuable in wet tropical climates (e.g. Bangladesh), where the water quality of surface water may vary greatly throughout the year. As a general rule, rainfall should be over 50 mm/month for at least half a year or 300 mm/year (unless other sources are extremely scarce) to make RWH environmentally feasible (HATUM & WORM 2006). In the following table, some examples are given for annual rainfall in different regions (HATUM & WORM 2006).

Catchment Area

To be ‘suitable’ the roof should be made of some hard material that does not absorb the rain or pollute the run-off. Thus, tiles, metal sheets and most plastics are suitable, while grass and palm-leaf roofs are generally not suitable (THOMAS & MARTINSON 2007).

Delivery System

A variety of guttering types. Source: HATUM & WORM (2006)

The delivery system from rural rooftop catchment usually consists of gutters hanging from the sides of the roof sloping towards a down pipe and tank. Guttering is used to transport rainwater from the roof to the storage vessel. Guttering comes in a wide variety of shapes and forms, ranging from the factory made PVC type similar as the pipes used in water distribution systems) to home made guttering using bamboo or folded metal sheet. Guttering is usually fixed to the building just below the roof and catches the water as it falls from the roof (HATUM & WORM 2006).

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Example of a first flush device (white, vertical PVC pipe, left). Illustration of the working principle of the device (right). Source: DOLMAN & LUNDQUIST (2008)

Debris, dirt, dust and droppings will collect on the roof of a building or other collection area. When the first rains arrive, this unwanted matter would be washed into the tank. This will cause contamination of the water and the quality will be reduced. Many RWH systems therefore incorporate a system for diverting this ‘first flush’ water so that it does not enter the tank. These systems are called first flush devices. Further information on first flush devices is provided in DOLMAN & LUNDQUIST (2008) and PRACTICAL ACTION (2008).

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Left: this filter (developed by WISY) fits into a vertical down pipe and acts as both filter and first-flush system. Right: filter cartridge of Pop-up-filter (developed by KSCST) acts as a first-flush separator. Source: CSE (n.y.), KSCST (n.y.)

The simpler ideas are based on a manually operated arrangement whereby the inlet pipe is moved away from the tank inlet and then replaced again once the initial first flush has been diverted. This method has obvious drawbacks in that there has to be a person present who will remember to move the pipe. Other, more sophisticated methods provide a much more elegant means of rejecting the first flush water, (described in PRACTICAL ACTION (2008), training material). But practitioners often recommend that very simple, easily maintained systems be used, as these are more likely to be repaired if failure occurs (PRACTICAL ACTION 2008).
A coarse filter, preferably made of nylon or a fine mesh, can also be used to remove dirt and debris before the water enters the tank (HATUM & WORM 2006).

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Storage Tanks

RTRWH in Urban Areas using a Plastic Tank. Source: VISHWANATH (n.y.)

There are almost unlimited options for storing rainwater. Common vessels used for very small-scale water storage in developing countries include plastic bowls and buckets, jerry cans, clay or ceramic jars, cement jars, old oil drums, empty food containers, etc. For storing larger quantities of water, the system will usually require a tank above or below ground. These can vary in size from a cubic metre (1000 litres) up to hundreds of cubic metres for large projects (PRACTICAL ACTION 2008). For domestic systems volumes are typically up to a maximum of 20 or 30 cubic metres (PRACTICAL ACTION 2008). Surface tanks are most common for roof collection. Materials for surface tanks include metal, wood, plastic, fibreglass, brick, inter-locking blocks, compressed soil or rubble-stone blocks, ferro-cement and reinforced concrete. The choice of material depends on local availability and affordability. The material and design for the walls of sub-surface tanks or cisterns must be able to resist the soil and soil water pressures from outside when the tank is empty. Tree roots can damage the structure below ground. Careful location of the tank is therefore important (HATUM & WORM 2006).
There are a number of different methods used for sizing the tank. These methods vary in complexity and sophistication. PRACTICAL ACTION (2008) gives an overview over three different methods. Some are readily carried out by relatively inexperienced, first-time practitioners, while others require computer software and trained engineers who understand how to use this software. The storage requirement will be determined by a number of interrelated factors, which include: local rainfall data and weather patterns, size of roof, runoff coefficient (depending on roof material and slope) and user numbers and consumption rates.
In reality the cost of the tank materials will often govern the choice of tank size. In other cases, such as large RWH programmes, standard sizes of tank are used regardless of consumption patterns, roof size or number of individual users (although the tank size will, hopefully, be based on local averages) (PRACTICAL ACTION 2008).

Infiltration

Collected water can also be used for replenishing a well or the aquifer (see also surface or subsurface artificial groundwater recharge). In a case study of SHRESTHA (2010), excess rainwater during the rainy season is used to recharge a dug well, as well as the groundwater. In this case recharging the groundwater even improved the water quality in the dug well.

User Behaviour

Depending on the user behaviour the storage and treatment (water quality) infrastructure is probably different. In some parts of the world, RWH is only used to collect enough water during a storm to save a trip or two to the main water source (open well or pump). In this case only a small storage container is required. In arid areas, however, people strive to create sufficient catchment surface area and storage capacity to provide enough water to meet all the needs of the users (HATUM & WORM 2006).
Four types of user regimes can be discerned:
Occasional - Water is stored for only a few days in a small container. This is suitable when there is a uniform rainfall pattern and very few days without rain and there is a reliable alternative water source nearby.
Intermittent - There is one long rainy season when all water demands are met by rainwater, however, during the dry season water is collected from non-rainwater sources. RWH can then be used to bridge the dry period with the stored water when other sources are dry.
Partial - Rainwater is used throughout the year but the ‘harvest’ is not sufficient for all domestic demands. For instance, rainwater is used for drinking and cooking, while for other domestic uses (e.g. bathing and laundry) water from other sources is used.
Full - Only rainwater is used throughout the year for all domestic purposes. In such cases, there is usually no alternative water source other than rainwater, and the available water should be well managed, with enough storage capacity to bridge the dry period.

Cost Considerations

Run-off from a roof can be directed with little more than a split pipe or piece of bamboo into an old oil drum (provided that it is clean) placed near the roof. The water storage tank or reservoir usually represents the biggest capital investment element of small-scale rooftop urban rainwater harvesting system and therefore require careful design to provide optimal storage capacity while keeping the cost as low as possible. Installing a water harvesting system at household level can cost anywhere from USD 100 up to USD 1000. It is difficult to make an exact estimate of cost because it varies widely depending on the availability of existing structures, like rooftop surface, pipes and tanks and other materials that can be modified for a water harvesting structure. Expensive systems with large tanks deliver more water than cheaper systems with small tanks (THOMAS & MARTINSON 2007).

Health Aspects

Rainwater itself is of excellent quality, only surpassed by distilled water – it has very little contamination, even in urban or industrial areas, so it is clear, soft and tastes good. Contaminants can however be introduced into the system after the water has fallen onto a surface (THOMAS & MARTINSON 2007).

Firstly, there is the issue of bacteriological water quality. Rainwater can become contaminated by pathogenic bacteria (e.g. form animal or human faeces) entering the tank from the catchment area. It is advised that the catchment surface always be kept very clean. Rainwater tanks should be designed to protect the water from contamination by leaves, dust, insects, vermin, and other industrial or agricultural pollutants. Tanks should be sited away from trees, with good fitting lids and kept in good condition. Incoming water should be filtered or screened, or allowed to settle to take out foreign matter. Water, which is relatively clean on entry to the tank, will usually improve in quality if allowed to sit for some time inside the tank. Bacteria entering the tank will die off rapidly if the water is relatively clean. Algae will grow inside a tank if sufficient sunlight is available for photosynthesis. Keeping a tank dark and sited in a shady spot will prevent algae growth and also keep the water cool. As mentioned above, first flush devices help to prevent the dirty ‘first flush’ water from entering the storage tank. The area surrounding a RWH should be kept in good sanitary condition, fenced off to prevent animals fouling the area or children playing around the tank. Any pools of water gathering around the tank should be drained and filled (PRACTICAL ACTION 2008).
Secondly, there is a need to prevent insect vectors from breeding inside the tank. In areas where malaria is present, providing water tanks without any care for preventing insect breeding can cause more problems than it solves. All tanks should be sealed to prevent insects from entering. Mosquito proof screens should be fitted to all openings (PRACTICAL ACTION 2008).

Working Principle	Rainwater collected on the rooftop is transported with gutters to a storage reservoir. There is a wide variety of systems available for RWH systems as well as for treating water before, during and after storage, which helps to prevent water from contamination.
Capacity/Adequacy	The supply is limited by the amount of rainfall and the size of the catchment area and storage reservoir (HATUM & WORM 2006). Storage reservoirs can vary in size from a cubic metre up to hundreds of cubic metres for large projects, but typically up to a maximum of 20 or 30 cubic metres for a domestic system (PRACTICAL ACTION 2008).
Performance	Rainwater is generally better quality than other available or traditional water sources (groundwater may be unusable due to fluoride, salinity or arsenic; HATUM & WORM 2006).
Costs	100 to 1000 USD depending on material, storage size and technology.
Self-help Compatibility	Depending on the scale, construction of RWH systems can be very simple and local people can easily be trained to build these themselves. This reduces costs and encourages more participation, ownership and sustainability at community level (HATUM & WORM 2006).
O&M	Proper operation and regular maintenance is a very important factor that is often neglected. Regular inspection, cleaning, and occasional repairs are essential for the success of a system (HATUM & WORM 2006).
Reliability	If well constructed and maintained drinking water in good quality is available.
Main strength	It provides water, which otherwise would have been lost, at the point of consumption (HATUM & WORM 2006).
Main weakness	Limited supply: The supply is limited by the amount of rainfall and the size of the catchment area and storage reservoir (HATUM & WORM 2006).

Applicability

RTRWH in urban areas can be implemented everywhere from a single household to community level (SHRESTHA 2010): the technology is flexible and adaptable to a very wide variety of conditions. It is used in the richest and the poorest societies, as well as in the wettest and the driest regions on our planet. Collected rainwater can supplement other water sources when they become scarce or are of low quality like brackish groundwater or polluted surface water in the rainy season. It also provides a good alternative and replacement in times of drought or when the water table drops and wells go dry. (HATUM & WORM 2006).

Advantages

• Local people can easily be trained to build RWH systems themselves. This reduces costs and encourages more participation, ownership and sustainability at community level (HATUM & WORM 2006)
• Rainwater is better than other available or traditional sources (groundwater may be unusable due to fluoride, salinity or arsenic) (HATUM & WORM 2006)
• Costs for buying water and time to extract from the city water supply can be saved (SHRESTHA 2010)
• It provides water at the point of consumption (HATUM & WORM 2006)
• Not affected by local geology or topography (HATUM & WORM 2006)
• Almost all roofing material is acceptable for collecting water for household purposes (HATUM & WORM 2006)
• Rooftop RWH reduces the amount of rainwater going into sewers, drains and may reduce flooding and clogging of water channels and uptakes (WATERAID 2008)

Disadvantages

• Limited by the amount of rainfall and the size of the catchment area and storage reservoir (HATUM & WORM 2006)
• Supply is sensitive to droughts: Occurrence of long dry spells and droughts can cause water supply problems (HATUM & WORM 2006)
• The cost of rainwater catchment systems is almost fully incurred during initial construction (HATUM & WORM 2006)
• Proper operation and regular maintenance is a very important factor that is often neglected (HATUM & WORM 2006)
• Rainwater quality may be affected by air pollution, animal or bird droppings, insects, dirt and organic matter (HATUM & WORM 2006)

References

CPREEC (Editor) (n.y.): Rooftop Rainwater Harvesting System. Tamil Nadu: C.P.R. Environmental Education Centre (CPREEC). URL [Accessed: 11.03.2011].

CSE (Editor) (n.y.): Filters developed by WISY. New Delhi: Centre for Science and Environment (CSE). URL [Accessed: 05.01.2011].

HATUM, T.; WORM, J. (2006): Rainwater Harvesting for Domestic USE. Wageningen: Agrosima and CTA. URL [Accessed: 11.03.2011].

PRACTICAL ACTION (Editor) (2008): Rainwater Harvesting. Bourton on Dunsmore: Practical Action, Schumacher Centre for Technology & Development. URL [Accessed: 11.03.2011].

KSCST (Editor) (n.y.): Rainwater Harvesting Filter – “PopUp Filter” – Karnataka. Bangalore: Karnataka State Council for Science and Technology (KSCST). URL [Accessed: 05.01.2011].

RAINWATERCLUB (Editor) (n.y.): Rainwater Harvesting: Rain barrel. Bangalore: RAINWATERCLUB. URL [Accessed: 11.03.2011].

SHRESTHA, R.R. (2010): Eco Home for Sustainable Water Management- A Case Study in Kathmandu. Kathmandu: United Nation Development Program (UNDP). URL [Accessed: 05.01.2011].

THOMAS, T.H.; MARTINSON, D.B. (2007): Roofwater Harvesting: A Handbook for Practitioners. Delft: IRC International Water and Sanitation Centre. URL [Accessed: 11.03.2011].

VISHWANATH, S. (n.y.): Rainwater Harvesting in Urban Areas. Bangalore: RAINWATERCLUB. URL [Accessed: 11.03.2011].

WAN (Editor) (2008): Nepal’s Experiences in Community-Based Water Resource Management. (= Fieldwork paper). Water Aid Nepal (WAN) and End Water Poverty. URL [Accessed: 30.03.2010].
 Thanks
 http://www.sswm.info/category/implementation-tools/water-sources/hardware/precipitation-harvesting/rainwater-harvesting-u