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Rainwater Harvesting

Immediate water security measures (Short & Medium Term)

Sustainable water security measures (Long Term Measures)

Rain/Roof water harvesting, storage and controlled use (FC tanks, lined ponds etc.)

Attitudinal and Behavioural Change (ABC) relating to water use & water literacy

Natural GWR Agronomic & vegetative measures

Engineering measures leading to Groundwater Recharge

Rain/Roof water harvested into Rain pits and Staggered Contour trenches

Land Improvement Measures

Drainage line treatment

urban

Rural

A house of 100 m²will generate

100*3*0.8= 240 m³ = 2,40,000 litres of water in a year

(Av. annual rainfall of the region is 300 cm and runoff coeff. of tiled roof is 0.8)

A family of 4 will require

in 1/3 period of an year

135x4x365=65,700 litres

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Well

Collection Surface

Gutter system

First flush system

Tank

Filter

Well recharge

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TECHNO-ECONOMIC EVALUATION OF A MULTI-MEDIA VERTICAL FLOW FILTER FOR ROOFWATER HARVESTING

Dr. Manoj P. Samuel

Executive Director

KSCSTE- Centre for Water Resources Development and Management, Kozhikode, Kerala, India

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Introduction

Besides upon incidence on the earth surface and generation as runoff, the rainwater undergoes a series of quality changes through contamination and pollution.
The major pollutants in roof water include organic matter, inert solids, fecal deposits from animals and birds, trace amounts of metals, and complex organic compounds.
Need to design, develop and evaluate location specific, bio-degradable, hydraulically efficient and cost-effective filtration mechanisms for roof water harvesting.

To design and evaluate hydraulically efficient filtration mechanism for roof water harvesting
To evaluate the economic viability of the filtration mechanism developed.
To evolve a Water Quality Decision Support System (WQ-DSS) in tandem with the developed filtration mechanism.

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Inlet water Quality

Inlet water Quantity

Data collection and analysis

Rainwater

Roofwater

Stormwater

Met data

Catchment details

Roofwater filter- Lab model

Sorption test

Column study

Hydraulic Efficiency tests

Filter effectiveness trials

Ranking of Media, Screens and Filter combinations

Modeling roofwater filter

Field evaluation of best filter

Developing DSS

Economic Analysis

Selection of filter media

Filter Media	Screens	Proportions
Gravel- Charcoal (Coconut shell)-Sand (GCsS) (M1)	Non-Woven Sisal Coir (NWSC) (S1)	1 : 1 : 1 (P1)
Gravel- Charcoal (Wood)-Sand (GCwS) (M2)	Aluminum mesh (S2)	3 : 1 : 2 (P2)
Gravel-Anthracite-Sand (GCS) (M3)	Nylon (S3)	1 : 2 : 3 (P3)
	No screen (S4)	2 : 3 : 1 (P4)

Methodology

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Step I

Step IV

Step III

Vertical Filters- 48 combinations- Hydraulic efficiency test

Best Media, Proportion and combination

superior filter combinations , media and proportion were selected which exhibited significantly higher performance based on its UPI values

Field Evaluation

Preparation of DSS

ANOVA Duncan’s MRT

Step V

Visual C⁺⁺

Step II

Vertical Filters- 48 combinations- Pollutant removal efficiency test

Best Media, Proportion and combination

UPI (Universal Performance Index)

where, HE = hydraulic efficiency

QIE_i= quality improvement efficiency with respect to i^th parameter

n = total no of chemical parameters tested

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Key findings

The proportion P1 (1:1:1), media M3 (S-Anthracite-G), screen S1 (NWSC) and combination P1M1S1 (gravel-shell charcoal-sand in 1:1:1) were found to be the best

Type of filter	Cost of filtration/m³ ( )	NPV ( )	IRR (%)	BC ratio
Roof water	17.75	345.64	22	1.07

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DSS on Water Quality

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For roofwater filters, the anthracite media, Non Woven Sisal-Coir screen and 1:1:1 proportions are good.
The best filter combination in case of roofwater filters is gravel-shell charcoal-sand in 1:1:1 proportion separated by NWSC meshes.
The sand-charcoal-gravel roofwater filter is very good in removing chemicals such as K⁺, Na⁺, PO₄^2-and NO₃^-, but they are not recommended for removing Ca²⁺ and Mg²⁺.
Based on the estimated annual costs and returns, all the financial viability criteria (IRR, NPV and BCR) are found favourable and affordable by farmers.
The natural fibre filter media and screens used in this study are cheap, environmentally compatible and biodegradable, with raw materials that are commonly available and renewable in nature.
The DSS tool developed would help the farmers, engineers, environmentalists and general public to know the standards of raw water, its end use and type of filter.

Concluding Recommendations

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