Carrying a torch to dark zones


Helping themselves
Bank loans to harvest water
Where there's a will,there's
a way



Watershed development: what next


Creating their own water world
Simple yet effective


The dharma of water


Netherlands Development
Cooperation Programme



Concern for common resources
Schools efforts
We beg to differ


A stark reality




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Vol. 2                                    No. 6                         December 2000

Creating their own water world

It is common knowledge that despite more than adequate rainfall, India faces acute water shortage. The solution, as has been proven time and again, is to catch water where it falls. Keeping, precisely that in mind, the 'Inspiration'* team, has planned and executed a fully decentralised water and waste management system for the BTH group of hotels in Ernakulam, Kerala. The water requirement (20,000 litres per day and nonpotable are 9,000 litres per day) for the first stage of the hotel and convention project is attempted to be met by a combination of rainwater harvesting and waste water treatment and recycling.

The project named BTH Sarovaram, is located six kilometres south of Ernakulam, along the NH 47 bypass. The site extends on an area of approximately two hectares. Surface wells in the area yield only brackish water. BTH opted for rainwater harvesting and other water management systems for making the hotel self sufficient.

The catchment areas
Roofs with reinforced concrete cement (RCC) slabs, roof area with thatch, surface area of lake and surface runoff, amounting to a total design catchment area of 6289.38 square metres.

a) Rainwater harvesting from roofs
Water is collected along the sides of roof through aluminum drains. It is then passed through a simple roughing filter and let into the lake through drainpipes laid along the site. The average section of 150 mm x 125 mm are provided for the drain taking into consideration peak rainfall data.

b) Subsurface drains
Surface runoff is also directed into the lake for recharging. Conventional stormwater drains besides being expensive need recurring cleaning and maintenance. To overcome this, sub-surface drains were designed. These drains consist of a 50mm PVC open joint pipe placed within a trench drain 0.5-0.6 metres deep to enhance the carying capacity of the drain. A mesh covered by polypropylene fabric (PP) protects the joints of the pipe. A stepped excavation of the trench is adopted to facilitate placement of fabric. After wrapping crushed stone with PP fabric, the top part of the trench is filled with coarse sand. Finally, dry stone pitching completes the top surface.The entire surface run-off thus drained is collected in sump tanks at the west end of the site (which is the lowest portion). The water quality is monitored regularly and if within accepted standards is pumped back to the lake.

c) Lake
The basic guideline in deciding the size of the lake was that it should provide sufficient reserves for the dry months. Taking consumption and evaporation into consideration, it was decided to give a total volume of approximately 40 to 50 lakh litres (storage volume for 4 months duration).

Cottage block at BTH Sarovaram, overlooking the artificially created reservoir

Cement stabilized red earth soil was used for basic lining. For the sides clay lines were used. On top of the clay, after proper wetting, a protection of jute-HDPE composite lining was given to retain the moisture in the clay. Then the fabric was given a coating of cement slurry to make it resistant to rodent attack. Finally, for protection of the HDPE from ultra violet radiation random rubble pitching was done.

Purification system of the lake
The purification of the lake is done through a simple coagulation and pre-chlorinating followed by settling, filtration, and post chlorinating.Water is also led to an activated carbon filter for removal of odour, traces of algae and residual chlorine.

Sewage and waste water disposal
The soil wastes (black water) are collected separately, led through anaerobic filters and the treated effluent is let off to the backwaters after chlorinating.

Wastewater treatment and recycling system
To optimise the usage of water, grey water (from kitchens and bathrooms) is treated and reused for nonpotable end uses. Since the treatment system requires gravity, the sewage is pumped to an elevated terrain and then let down.

The water is then directed to upflow filters for removal of solid particles and also for partial Biological Oxygen Demand (BOD) reduction through anaerobic action. The effluent is pumped to multistage constructed wetlands/reed beds at the top of the mount. Treated effluent is collected in a polishing pond, where the final polishing and BOD removal is effected mainly by water plants like duck weed. This water is chlorinated and pumped to the overhead tank for flushing, gardening and other non-potable end uses.

*‘Inspiration’ is a team of architects and planners, infrastructure engineers and technical experts, construction management, trained artisans, craftsmen and technicians.

For further information:
Latha Raman,
Director - Infrastructure, Inspiration,
Opp. Lakshmi Hospital, Diwans Road, Ernakulam - 682 016, Kerala
Phone: 0484 - 353402, 352499
Fax: 0484 - 369899

Copyright CSE  Centre for Science and Environment