Scholarly article on topic 'Eco-Friendly, Water Saving Sanitation System'

Eco-Friendly, Water Saving Sanitation System Academic research paper on "Materials engineering"

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{"Water Consumption" / "Closing the loop" / "Eco toilets ;"}

Abstract of research paper on Materials engineering, author of scientific article — R.K. Ihalawatta, K.A.B.N. Kuruppuarachchi, A.K. Kulatunga

Abstract Sanitation facility is among the main living requirements of mankind. It should be more hygienic and easy. Presently, many existing sanitation systems extensively depended on pipe borne water. On the contrary, some parts of the world experiences water scarcity and that has led to un-hygiene sanitation systems. In terms of eco efficiency, even the hygienic sanitation systems have more opportunity to improve. Inefficient water consumption and none usage of nutrients available in excreta in a useful manner are main culprits. Since nutrients available in excreta are not returned to soil breaks the nutrient cycle, end up with less fertile soil which could not directly use for agricultural purposes. Therefore, this research focuses on design and developing an eco-friendly sanitation system, on ancient which minimize pipe borne fresh water usage for sanitation while facilitating nutrients mixing to soil in order to enhance soils fertility based eco-friendly filtering mechanism. The proposed system has three focused areas: water saving option, eco-friendly digestion method with a business model. The new design reduces water consumption with the assistance of manually operated mechanical suction system. An energy free digestion mechanism handles the solid part of excreta. Bio degradable cheap or freely available material is used as filtration media and replaceable blocks have been designed for easiness to operate the new method. Since proposed system facilitate re-usage of black water and digested excreta on biodegradable media as fertilizer while closing the loop of the cycle of nutrients, proposed system can be branded as eco-friendly sanitation system.

Academic research paper on topic "Eco-Friendly, Water Saving Sanitation System"

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ScienceDirect

Procedía CIRP 26 (2015) 786 - 791

12th Global Conference on Sustainable Manufacturing

Eco-Friendly, Water Saving Sanitation System

R.K.Ihalawattaa, K.A.B.N.Kuruppuarachchib,A.K.Kulatunga*

department of Production Engineering, University of Peradeniya, Sri Lanka. 2Department of Production Engineering, University of Peradeniya, Sri Lanka.

* Corresponding author. Tel.: +9-471-822-2535; fax: +9-481-239-3655. E-mail address: aselakk@pdn.ac.lk

Abstract

Sanitation facility is among the main living requirements of mankind. It should be more hygienic and easy. Presently, many existing sanitation systems extensively depended on pipe borne water. On the contrary, some parts of the world experiences water scarcity and that has led to un-hygiene sanitation systems. In terms of eco efficiency, even the hygienic sanitation systems have more opportunity to improve. Inefficient water consumption and none usage of nutrients available in excreta in a useful manner are main culprits. Since nutrients available in excreta are not returned to soil breaks the nutrient cycle, end up with less fertile soil which could not directly use for agricultural purposes. Therefore, this research focuses on design and developing an eco-friendly sanitation system, on ancient which minimize pipe borne fresh water usage for sanitation while facilitating nutrients mixing to soil in order to enhance soils fertility based eco-friendly filtering mechanism. The proposed system has three focused areas: water saving option, eco-friendly digestion method with a business model. The new design reduces water consumption with the assistance of manually operated mechanical suction system. An energy free digestion mechanism handles the solid part of excreta. Bio degradable cheap or freely available material is used as filtration media and replaceable blocks have been designed for easiness to operate the new method. Since proposed system facilitate re-usage of black water and digested excreta on biodegradable media as fertilizer while closing the loop of the cycle of nutrients, proposed system can be branded as eco-friendly sanitation system.

© 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of Assembly Technology and Factory Management/Technische Universität Berlin. Keywords: Water Consumption; Closing the loop; Eco toilets;

1. Introduction

Sanitation of human should be hygienic, safe, easy and eco-friendly. Conventional water based sanitation facilities are satisfying all the requirements except the environmental efficiency which is more important. They usually flush the excreta and store them in a pit. Excreta should return to the soil as nutrients, it is formed by absorbing the nutrients by soil and they should be return back for the sustainability of soil. The flush also done inefficiently as it consumes more fresh water even for flushing a less amount of excreta. These major disadvantages can be roots for many other problems.

There existing people even in Sri Lanka, with lack of fresh water for their basic needs while a huge amount of fresh water is being wasted for flushing excreta. And also people in lower lands of Sri Lanka are facing a risk of getting kidney diseases due to the vast use of chemical fertilizers mostly done in upper

lands. Excessive use of chemical fertilizers can harm the soil in an unrecoverable manner. Discontinuity of natural nutrient cycle is the major reason for poor soil which can be converted to a closed loop by nutrients in excreta back to soil.

Several sustainable sanitation systems are recently introduced in order to reach the main goals of reducing water consumption and reusing excreta. Urine diverting toilets has become more popular today [1]. Vacuum toilets save more than half of water used in the conventional flush system, but most of them are consuming energy and complex in the arrangements [2]. A toilet with separate pits for solid and liquid were practiced in rural Mexican schools and similar kind of composting pits with portable toilet slab method was being practiced in Zimbabwe [1]. But they are less user friendly, less hygiene and cannot be used in modern residences.

Ancient Sri Lankan technology also supplies several examples in sustainable sanitation. Urine was diverted and has been sent

2212-8271 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of Assembly Technology and Factory Management/Technische Universität Berlin. doi:10.1016/j.procir.2014.07.165

through several material such as charcoal and lime for purification in ancient sanitation facilities found in monasteries in ancient cities of Sri Lanka [3]. A new design of sustainable sanitation system with less water consumption, Solid and liquid separation method, Excreta reusing method and urine re-using method for plantations closing the loop of the cycle of nutrients is necessary to overcome above challenges.

The designed Sustainable sanitation system is mainly focused on separating solid and liquid waste and treating them separately to a state of reusing for plants. Urine is separated initially at the pit by a urine diverting system. A special filtering plate is designed which will soak black water through, by holding excreta.

Current water consumption per flush is planned to be reduced by introducing both air and grey water as the washing media. The system is designed to be more economical by using inexpensive waste material for the digesting, reducing water consumption and by replacing chemical based fertilizers with homemade organic fertilizers still holding the hygienic and social aspects of the current system. By turning solid waste into rich fertilizer and by re-using the filtered (treated) black

water for cultivation, food nutrient cycle has been converted in to a close loop system.

2. Methodology

The proposed methodology partially based on the ancient urinal systems which were available in centuries ago. As shown in Fig 1 this methodology consists of three main stages. In the first stage, fresh water reduction for the flushing is reduced, in the second stage, develop a method to produce Terra Preta fertilizer from waste and in the final stage, a sustainable business model is developed.

2.1 Reduce the fresh water consumption for flushing

Normally a person use 4 liters of fresh water per flush. Consuming this much fresh water is not sustainable. In the present there are several vacuum suction toilets to reduce the water consumption. All of them are powered by electricity. In this sustainable sanitation system, a mechanically operated vacuum suction system is introduced. Other than the vacuum toilet system a gray water system is installed in to the sanitation model to reduce the fresh water consumption.

Fig 1: methodology flow chart

Mechanical vacuum suction system

The suction system is operated manually by using the user energy. Totally electricity free system is designed such a way that it will reduce the water consumption. The sustainable sanitation system uses a vacuum suction on the waste. Basically the water is used on the flushing process to wash off the excreta which were deposited on the commode walls. So by dropping the excreta in to a bawl full of water, the depositing of excreta on the commode walls is almost zero. And the pushing of waste in to the drainage pit is eased out by sucking the whole mixture of excreta and water in by using a

vacuum suction. The designed new flushing system is as follows in Fig 2.

Gray water system for flushing water

Fig 2. The vacuum flushing system A piston cylinder arrangement can be used to make the vacuum and to transfer the excreta to the drain with water. And by making an energy free vacuum system, a sustainable flushing process is achieved. After the waste removal job and the anal cleaning are done, the user can push the flushing lever down until the water and excreta mixture sucked down to the drainage pit. When the flushing lever goes down the piston inside the drainage line is pushed down. Initially this lower end of the piston is at 'A' and it goes up, until position 'B' the drainage pipe from the commode is blocked by the piston. And due to the non-return valve at the bottom end, air is not sucked in through the bottom side as the piston goes up. So due to this scenario, a vacuum is created between 'A' and 'B' positions. When the lower end of the piston passed the point 'B', the commode pipe line is opened and the whole waste mixture inside the commode will be sucked out by the vacuum.

And there is a urine separation feature in the commode. In the traditional systems in Sri Lanka this urine separation is one of the main features which are used. By separating urine in the beginning and most importantly before urine touches with the excreta, the growth of harmful pathogens will be reduced. And this separated urine will be a very concentrated urea composition, which can be stored and used as a rich fertilizer.

The vacuum system is applicable to multi floor buildings as well. Energy free vacuum system gives a great power saving than the currently used vacuum toilets.

One of the main features in this energy free vacuum toilet is that it have higher level of trapped water inside the commode, when excreta comes out of the human body quickly it dropped in to the water and sealed itself. No chance for pathogens or bacteria to connect with the atmosphere. The percentage water saving of an existing vacuum toilet is about 50%. With the sustainable vacuum toilet, the water saving can be achieved without consuming any electricity.

The grey water usage will reduce large percentage of fresh water consumption for flushing of toilets. But the grey water from kitchen sinks was left behind in this design due to the bad smell of the kitchen waste. So the grey water used in bathing and washing clothes was mainly contributed in this system. In the designed new system the grey water is collected and used as shown below in Fig 3. Reduction of fresh water consumption only can be done to a certain extend. Because some amount of water is essential for flushing and anal cleaning. But the flushing water amount can be further reduced by using this grey water instead of using fresh water for flushing. As shown, the washing and bathing water from bathrooms are collected into a filtration tank to remove the small particles and then after filtering the water is transferred to a storage tank by using gravity force.

Fig 3. The grey water collecting system

. Then the filtered grey water is pumped up in to an overhead tank by using a water pump. By using the grey water, fresh water consumption is reduced further.

2.2 Fertilizer production from the waste

The fertilizer production is done by digesting the excreta with mixing them with easily available, cheap and natural materials such as coir dust, wood shavings, ash and charcoal. The fertilizer production stage is mainly done within the drainage pit complex. This proposed pit complex consists of three main components. Storage vault, drainage pit and the soakage pit. As shown in Fig 4 the waste is dropped in to the drainage pit and the excreta and black water are separated through the waste separation plate. The plate consists of small holes and has a little inclination to ease up the separation.

Drainage pit

Fig 4. Fertilizer production setu

As shown in the Fig 4, excreta drop in to the drainage pit and the black water is soaked through the separation plate. And the solid excreta remain on the plate. Throughout the day excreta is collected on the plate. At the end of the day the pushing lever is pushed by the user and the excreta is moved into the storage vault. Storage vault is the place, where the excreta remain for a long time (8 to 12 months)[4] and digest in to the fertilizer. After a certain level of black water inside the drainage pit, the black water level is maintained by using a soakage pit. All the excess black water is flood in to the soakage pit. And the water and the nutrients are soaked in to the soil. The water and the excreta are separated at the beginning to create a low moisture condition inside the storage vault. Low moisture conditions increase the rate of digesting. After moving the excreta into the vault, the digesting material mixture is added on top of the excreta from top of the storage vault. This material addition reduces the odor and it increases the digesting rate. The digesting materials have different qualities towards making fertilizer. Wood shavings are to increase the temperature inside the vault and maintain the low moisture conditions, the ash is to increase the PH value of the fertilizer and all the materials are to increase the quality of the fertilizer.[4] The separated urine is used as a urea rich fertilizer, after diluting it with water. The sustainable sanitation system is energy saving and robust. The robustness of the system can be evaluated by a Failure mode and effect analysis (FMEA). Several failure modes have identified and the effects and the courses of those failure modes have evaluated. Ranking of the process stages are as shown in Table 1. The process stages are ranked according to the RPN (Risk priority number) of those stages. And the occurrence and the detection of those failures are determined according to the standard FMEA scale. The following results were taken using the ReliaSoft Xfmea software, Xfmea tool.

Table 1. Ranking of the process stages according to the RPN

Stage Description Failure mode RPN

6 excreta moved in to the storing vault 3 642

3 Water filling in to the toilet pan 2 640

5 Water separation at the separation plate 2 616

7 Digesting material addition 3 548

8 Extraction of composted fertilizer 2 432

2 Flushing the toilet 2 230

4 Excreta flows in the drainage pipe 1 60

1 Sitting on the toilet pan 1 10

Fig 5 and Fig 6 shows the initial occurrence/ severity matrix and the matrix after the preventive actions

Fig 5. Initial occurrence/ severity matrix

By the FMEA the system has become more robust after the preventive actions for the possible failures. At the initial stage as shown in Fig 5 all the failure causes are high priority ones (Triangles in red color).

After the preventive actions for the possible failures, the risk priority reduces and some of the high priority causes become low and medium priority causes as shown in Fig 6. The medium priority causes are in yellow color and the low priority causes are in green color.

Occurrence/Severity Matrix (Revised Ratings)

ilfflfe-

A A A A

2 O O A A O A ▼

S&ffissF

4 se^ 6

Fig 6 . Revised occurrence/ severity matrix

2.3 Business model for the sustainable sanitation system 2.3.1 Life cycle cost analysis (LCCA)

LCCA is an economic method of product evaluation in which all costs arising from owning, Operating, Maintaining and ultimately disposing of a product. LCCA provides a significantly better assessment of the long term cost effectiveness than focusing only the initial cost or operating cost of the product. All the costs are calculated here are with the assumption that the generally required piping and the building for the system is provided. Which means the costing hereby will expose the additional costs than an ordinary system. The life span of the proposed system is assumed as 10 years. Life cycle cost for the proposed sanitation should be an accumulation of all the following costs. 1. Initial Cost (Purchase cost), 2. Infrastructure preparation cost, 3.Installation Cost 4. Operation Cost, 5.Maintenance Cost 6. Disposal Costs Initial cost

Initial cost for the sanitation system is the purchasing price of the suction mechanism and the urine diverting pan for the customer. A manufacturer can produce the proposed design for LKR 117,927K and with the transportation and handling cost and manufacturer's profit, the customer can purchase the system for 129K (other costs are assumed as 10% of the price).

Infra-structure preparation cost

The system is designed to work with specially designed pit complex. The pit should be built in the premises of the person who purchase the system. The cost for the pit complex will be LKR 249,373. Installation cost

Once the pit is built and the system is flushed the buyer should install the system at their premises. This will create a cost for assembling, testing and installing the system of a

buyer. This cost is taken as the cost of hiring a technician for 10 hours. Then the cost for the installation will be LKR 2K. Operation Cost

The required materials for the operation are mainly water, ash and coir dust. Electricity will be used for pumping water from an underground grey water tank to a tank at the higher level. Ash is freely available, 1kg of coir dust and 1kg of ash should be added daily and the cost for coir dust for 10 years considering inflation is LKR 268,252 and the total cost for electricity for 10 years for the grey water pump is LKR 1319.50. Totally grey water is used for flushing which will make the cost for water zero. Maintenance cost

The total system should be cleaned once for two years also piston and valves and waste separation plate. The cost for cleaning the system will be for the technicians. Technicians will charge LKR 2000 per a service. The piston also should be lubricated using grease twice a year. And also the water seal of excreta pushing lever should be changed twice a year. Disposal Cost

The system is disposed by using construction parts as landfill and the steel rods and bars as scrap steel. By selling the scrap steel an income also can be earned. The labor cost for the land will be LKR 1500 and the income by the scrap steel will be LKR 1000, which makes the disposal cost LKR 500. When all the phases are considered for 10 years the total cost of the investment is LKR 653,444

2.3.2 Value creation

The buyer can omit the cost they paid for water completely by using grey water from the first day of the installation. The conventional system consumes around 4liters of fresh water [6] which will be saved with the usage of grey water. After the first year the system is ready to produce fertilizer by digested excreta. It produces 50kg of fertilizer from the excreta [7] defecated by a person. As the system is designed considering five members for a family. The annual amount of fertilizer generated will be 250kg. Which can be sold to the farmers? The current price of 1kg of compost fertilizer is LKR 80 and If the fertilizer made by excreta is sold for LKR 60 the income yearly will be LKR15, 000. The saving of water per year is 21900 liters. The price of a unit of water in Sri Lanka is LKR70 and the money saved with water is LKR 1,533,000.

Thus the income of after the first year will be 1,548,000 which mean the total cost of LKR 653,444 can be recovered within after year.

2.3.3Creation of business opportunities

The system is designed for the domestic use of an ordinary family. Fertilizers made are itself saves a lot of money spent for chemical fertilizers. The excess production of fertilizer can be sold as a business opportunity, which can be done by the domestic users themselves. Fertilizer collecting and selling can be done as a business which will be a good chance for the current chemical fertilizer sellers to in cooperate with.

On the other hand the required digesting materials manufacturing and distributing will create a new production opportunity which will be more profitable as the materials used are cheap and readily available.

The current compost manufacture can used fertilizer formed by human waste as a raw material for their products. If the suction mechanism is used the maintenance should be done after a period which will create new employment. Someone can even start selling, fixing and servicing firms of sustainable sanitation systems.

2.3.4 Sustainability of the design

The system is both economically and environmentally sustainable as it closes the loop of nutrients by producing fertilizer which can be used for cultivation again and re using urine as a good nitrogen supplement.

As the life cycle cost analysis says, the system recovers the investment cost just after the first harvesting at the end of the first year. For the rest nine years the system will be producing only the profit which shows the economical sustainability of the system.

3. Discussion

[2] Gunter Langergrabera, Elke Muelleggera,Ecological Sanitation—a way to solve global sanitation problems Institute of Sanitary Engineering and Water Pollution Control, BOKU—University of Natural Resources and Applied Life Sciences, Vienna,Austria 22 January 2004.

[3] W.I.Siriweera Sanitation and health care in ancient Sri Lanka,by. The Sri Lanka Journal of the Humanities XXIX & XXX (I &2) 2003 & 2004.

[4] Construction of ecological sanitation latrine, Technical Hand book. A WaterAid in Nepal publication

September 2011.

[5]www.reliasoft.com/newsletter/2q2003/rpns.htm(last visited 17.7.2014)

[6]http://www.decd.sa.gov.au/docs/documents/1/WaterSmart ToiletsUrinals.pdf (last visited 20.7.2014).

[7] Case study of sustainable sanitation projects Household UDDTs in flood-response resettlement project Guara-Guara, Sofala province, Mozambique.

The proposed sanitation system produces fertilizer and it also has a methodology to apply urine to the crops, which returns the nutrients in human waste back to the soil closing the loop of nutrient. The system also consumes less water than the conventional system as it has a suction mechanism to suck the water out with excreta. According to the business analysis the system recovers the investment cost with the ending of the first year and the rest of the period will be totally profitable. In directly, the fertilizer formed in the system can be used for cultivation replacing the chemical fertilizers.

4. Conclusion

When the environmental and economic aspects are considered, the idea exposed shows that the proposed system is a sustainable system which can last for a longer period with economical profits and environmental contribution. The proposed sanitation system has functions for closing the loop of nutrients with respect to the environmental considerations. The proposed system has sustainable functions such as energy free vacuum suction, which reduces the energy usage and increase the resource efficiency of the sanitation system.

5. Reference

[1] Steven.A.Esrey Ingvar Andersson, Astrid,Hillers Ron Sawyer Closing the loop Ecological sanitation for food security by. Swedish International Delopment Cooperation Agency First Edition, 2001.