Modular Roof Top Rain Water Harvesting in Aligarh

RTRWH7  RTRWH4

Aligarh Development Authority (ADA) in Aligarh district of Uttar Pradesh is setting up a modular roof top rain water harvesting (RWH) unit atop the office of the Divisional Commissioner, Aligarh Division.  From water shortage to water abundance, the system will also enhance water quality and provide unlimited water storage capacity.

This was reported by a team of central government officers who visited the district on 8th August, 2019 as a part of the Jal Shakti Abhiyan (JSA) to inspect existing water conservation measures and begin new initiatives in rainwater harvesting, renovation of traditional and other water bodies/tanks; reuse and recharge structures; watershed development; and intensive afforestation.

RTRWH  RTRWH2  RTRWH3

According to Sudhir Kumar Gangadhar Rahate, Additional Secretary, Ministry of Power, who is the Central Nodal Officer (CNO) for the JSA campaign; ‘Modular RWH’ is a new technique for Roof Top Rain Water Harvesting. It is both convenient and easy to maintain in comparison to traditional RWH.

Difference between processes of traditional RWH and modular RWH systems

Step Traditional RWH Modular RWH
1 Roof top rain water is collected in a desilting chamber

 

Roof top rain water is collected in a chamber having 2 feet high partition wall. The water settles in the first part where most of the silt settles down and then overflows into the next.
2 From the desiltation chamber, water flows into the filter chamber, which has layers of pebble, gravel and sand occupying about one third of the chamber. The water percolates down through these layers. The filter material requires regular cleaning, which is a cumbersome process. From desiltation chamber, the water flows into a cylindrical drum having a filter mesh at the top.  Other suspended material such as leaves and silt is stopped here. This filter can easily be pulled out and cleaned at regular intervals.
3 The water after passing through the filter material enters into the recharge chamber having recharge well(s) going down to the aquifer material (generally discharged into aquifer through slotted pipe fairly above water level). The water after passing through the filter material enters into the recharge chamber having recharge well(s) going down to the aquifer material (generally recharged into aquifer through slotted pipe fairly above water level).

 

    In the next step, the water enters into an unlined chamber having recharge well (s) similar to traditional method. This chamber is packed by poly propelene blocks wrapped in Geotextile and back-filled with sand all around. The system allows receipt of water from all the sides. The well(s) recharge water into aquifer (generally recharged into aquifer through slotted pipe fairly above water level).

 

Unlike conventional RWH system, the recharge chamber in modular RWH need not be PCC/ RCC, thereby saving cost. Further, the PCC/ RCC Storage-cum-Recharge Tank after few years gets infested with algae/cobwebs and is very difficult to clean; whereas modular RWH with polypropylene blocks wrapped on all sides with geo-textile is almost maintenance free and its useful life is more with an option of portability if there is a need to use the occupied land for some construction purposes. Also, it has been the past experience that conventional RWH system always goes dysfunctional after 2-3 seasons whereas modular RWH system in its concept and design has addressed several factors that help them having many relative advantages over the conventional RWH system.

RTRWH5  RTRWH6

Other differences between the two methods are:

Sl. No Criteria Modular Method Conventional Method
1 Time taken for Installation  of tank 1 to 15 days irrespective of tank size 30 days to months to layout PCC, Brickwork, Plaster, Steel framework, Roof RCC
3 Space utilisation Top surface may be used for Parking lots; children’s play area, gardens, sports field. Generally located where land use is demarcated as unusable.
Requires overdesigning of cover slab to accommodate lawn or parking lots at surface level.
5 Environmental Impact Material is made up of 100% recycled Polypropylene (PP).
Eco friendly and qualifies for green rating
Virgin Material; Sourcing boulders and pebbles is a challenge, effecting our eco system.
6 Reduce / Extend/ relocate Tank size could easily be reduced or extended or even relocated as per future needs Requires construction of new tank, if future land requirement changes
8 Aesthetics Does not affect aesthetics of the property, rather helps to improve the same. Non Aesthetic
  Maintenance Very easy maintenance of filter bucket and desiltation chamber Cleaning of conventional filter material is very cumbersome, requiring removal of material from the chamber, cleaning/ replacement and relaying. Moreover, the conventional filter/ recharge chamber walls get infested with algae/cobwebs, etc.

Under Smart City Project, Aligarh Nagar Nigam is executing 2 conventional RWH schemes in Gandhi Park and another 3 conventional rooftop RWH systems in government buildings including Treasury Office.   Following the first visit of the central JSA Team, Aligarh Nagar Nigam decided to take up additional 20 rooftop RWH schemes for government buildings.  These will be a mix of conventional and modular rooftop RWH systems.

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