For rapidly increasing per capita water consumption in an emerging economy like India, Grey Water Recycling (GWR) systems appear to become in future a mandatory and inevitable component in residential and commercial facilities. Though such technologies are quite successful in Western nations but apparently high initial and investment costs tend to reduce the feasibility of such systems in India. This paper aims in analyzing the affordability of such systems considering the life cycle costs of such technologies which is a firm base for evaluating economic feasibility of such technologies.
Dr. Debasis Sarkar Associate Professor Mitul S. Shah M. Tech Student, Dept. of Construction & Project Management, Faculty of Technology, CEPT University. Ahmedabad.
IntroductionIndia faces serious water supply problems in many cities and hence measures have to be taken to conserve water or recycle the existing water. Greywater recycling is a very good technology through which the problems of water supply can be eased. Greywater means the household wastewater which has not been contaminated by toilet discharge water and thus includes wastewater from bathtubs, showers, bathroom washbasins, clothes washing machines, sinks and laundry tubs.
Affordability of such technologies has always been a contentious issue during feasibility and implementation studies. India is a developing country and every household still does not have enough financial capability to implement such systems. Thus an attempt has been made here to analyze the affordability of such systems considering the lifecycle of such technologies which is a sounder base for the feasibility judgment of such technologies.
Literature ReviewSchneider (2005) defines "Greywater" as "wastewater having the consistency and strength of residential domestic type wastewater. Greywater includes wastewater from sinks, showers, and laundry fixtures, but does not include toilet or urinal waters. He also states that if intended for applications other than subsurface irrigation (e.g. toilet flushing), greywater should not be stored unless biologically treated and disinfected. Left untreated, stored greywater can quickly become septic and develop a population of anaerobic bacteria that will proliferate and create noxious odours. Odours generated by storage prior to subsurface irrigation (i.e. within a septic tank) should be properly managed and ventilated in such a way as to not become a nuisance or result in accelerated corrosion of concrete structures (e.g. concrete septic tank, pipe, or distribution boxes).
Jarque et.al. (2008) recommends the direct reuse without storage as it minimizes the problems of microorganism growth and odor. However, even if storage is not required, each greywater system should be capable of handling sudden foreseeable inputs of greywater (for example from a bath being let out, or a washing machine rinse cycle) without overloading or saturating the soil
The potential economic benefit of supplementing water supply resources with the use of greywater is making it an issue of great interest to water authorities. Greywater reuse in gardens has the potential to replace about 18% of the current domestic water demand. In the Melbourne Urban System, this translates to overall savings of roughly 60 giga litres a year according to Shipton (2003). It has been estimated (Lechte, 1992) that water savings in the range of 18–29% for an average household could be achieved by reusing greywater.
Greywater Recycling Systems MethodologyGreywater is relatively clean but does contain significant quantities of food particles, grease, hair and detergents which can be difficult to filter and can clog membranes. Grey water can be used for flushing the toilet and garden irrigation, or for washing cars etc. It makes sense to use the cleanest source of grey water first, i.e. bath and shower water, followed by water from the bathroom sink. However, the main problem with grey water is how to deal with its storage. Within 24 hours of being stored without treatment, grey water goes "black" i.e. septic, but the technologies have developed in western countries which treat this grey water and convert it to usable form.
Data for the analysis of the economic feasibility of such systems was collected from two sites which are located in Mumbai and Ahmedabad respectively. Both sites have employed different versions and capacities of the greywater recycling systems. As the market for such systems in India is still at a nascent stage, they are not available readily in the Indian market. Thus foreign systems are used at both locations and the data for the same is given in Table 1. Case 1 is 3-BHK green building apartments which are being developed by a private developer and are nearby the developing Bhandup (Mumbai) area. There are in total 4 blocks which contains highrise apartments of 20 floors each and each floor has 2 flats. This makes a total of 40 flats per block. Grey Water Recycling system was installed for every such block and the details of the following are as follows.
|Table 1: Grey Water Recycling System Data (Case 1)|
|S. No.||Data Type||Value
(Capacity / Cost / Dimensions)
|1.||GWR System Type||3-Stage Filtration and Disinfection System||Steel Based System|
|2.||Size||2.5ft diameter x 5 ft long||One Module Size|
|3.||Capacity of the GWR System||5000 litres||Design Handling Rate for GWR System|
|4.||Filtration Rate||500 litres/ hr||Capacity wont be fully achieved|
|5.||Capacity of Adjoining Tank||5000 litres||Tank for only Block B|
|6.||Sedimentation Tank Capacity||350 litres||GW Held at this tank before filter|
|7.||Cost of Pipes||Rs. 45000. per Block||All Pipes for the System|
|8.||Submersible Pump Provided||15 HP||-|
|9.||Maintenance Costs||Rs. 25000. / Module||Approximate|
|10.||Maintenance Period||1 Year||-|
|11.||Cost||Rs. 1,50,000. / System||Total System minus Pipes|
|12.||Water Amount Generated for GWR||9600 litres / day||-|
Case II is a green commercial complex cum hotel building which is being developed by a private developer in Ahmedabad. The building is divided in two sections and for both the buildings, it is proposed that a common grey water recycling system would be installed. This grey water recycling system is to be imported from a German manufacturer. The details for such system are mentioned in Table-2.
|Table 2: GWR Systems Details for Case II|
|S. No.||Data Type||Value
(Capacity / Cost / Dimensions)
|1.||GWR System Type||2-Stage Filtration and Disinfection System||HDPE Polymer Based System|
|2.||Size||2ft diameter x 5 ft long||One Module Size|
|3.||Capacity of the GWR System||300 litres equivalent to 6000 litres||Design Handling Rate for GWR System|
|4.||Filtration Rate||75 litres / hr||Capacity wont fully be achieved|
|5.||Capacity of Adjoining Tank||7500 litres||Storage Tank|
|6.||Sedimentation Tank Capacity||NA||-|
|7.||Cost of Pipes||Included||All Pipes for the System|
|8.||Submersible Pump Provided||30 HP||-|
|9.||Maintenance Costs||Rs. 40000. / System||Approximate|
|10.||Maintenance Period||2 Year||NA|
|11.||Cost||Rs. 3,50,000 / System||Total System minus Pipes|
|12.||Water Amount Generated for GWR||15000 litres / day||-|
Calculation of Economic Feasibility
|Table 3: Life Cycle Cost of Proposed GWR System for Case I||Table-4: Life Cycle Cost of proposed GWR system for Case II|
Results and DiscussionThus from the above data we can apply the LCC formulas and find out the total cost of the implementation and maintenance of such systems which will help us in deciding whether the systems are actually feasible or not. The calculations are done as shown in the Table 5. The final costing is calculated in terms of cost / year / m2 of area which will be a helpful data in calculating the costs incurred by the residents according to the built up areas of their own houses.
|Table 5: LCC of the Two Systems for Case I and II|
|Data||Case I GWR System||Case II GWR System||Remarks|
|NPV (Rs.)||6,50,00||7,50,000||P/A, interest (i)= 10%, years (n)=20 is 8.5136.|
|Total area considered for analysis (m2)||140||140|
|LC C / m2 (Rs.)||4645||5350|
|Owning and Operating cost / year / m2 (Rs.)||390||447|
There is a considerable difference in the initial cost, as well as in the maintenance costs of the two systems. But the initial cost which is the most important parameter in our study is quite high for Case II and hence this system appears to be less feasible. The LCC of GWR system of Case I is observed to be Rs. 4645 / m2. and for Case II it is Rs. 5350 / m2. The owning and operating cost of the system for Case I is computed to be Rs. 390 / year / m2 and for Case II it is about Rs. 447. Considering a coverage area of about 80 m2 apartment for Middle Income Group (MIG) family the owning and operating cost would be Rs. 31,200./year which will amount to Rs. 2600. /month.
ConclusionConsidering the analysis of the above study, it is observed that the application of the Grey Water Recycling System is quite feasible in HIG housing schemes, but in affordable housing schemes the system seems to be less feasible. This is due to the higher initial costs and adequately high costs of operations and maintenance. Trends show that these models are quite successful in Western countries. With advancement of technology coupled with the increase in per capita income of urban households, the technology has tremendous potential and applicability in an emerging economy like India. Considering the rapidly increasing demand in per capita consumption of water in India, such systems would be inevitable in the future and hence extensive research is very important in this area. The systems could be made more economic and affordable by studying in details the system components and applying value engineering studies.
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