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How Good Design addresses Rainwater Harvesting maintenance issues Print E-mail


“The key issue is that good design based on real historical knowledge avoids most of the perceived maintenance problems – a high level of costly (and unnecessary) maintenance to counter marginal/ill-informed design choices is a very poor outcome indeed”.

Dr. Peter Coombes, March 2014, Sydney RHAA Breakfast


Summary

Using a quality management approach is a simple way to ensure rainwater is healthy, clean, clear and doesn’t smell.  Rainwater comprises a low public health risk and is drunk by over 2 million mainly rural Australians every day.

By considering the whole system and looking at potential problems any system can be designed to maintain high quality water. By designing multiple barriers through the rainwater harvesting process, for example gutter guards as well as a leaf diverter, water quality is improved through the process and water quality is protected even if one of the barriers fails.


A Quality Management Approach

The Australian Drinking Water Guidelines (ADWG) articulates a quality framework that incorporates good management practices to ensure water quality.  Several key elements from the ADWG system have been adopted to articulate a quality and risk management framework for rainwater system (RWS) design as follows:

  • Assess the intended end use for the water and any specific needs of the end users. Water delivered should be fit for purpose
  • Assess the site and location specific contamination risks (what type and what load of contaminants are expected)
  • Design, install and operate the rainwater system to provide progressive sequential redundant barriers to collection and distribution of contaminants
  • Each stage in the sequence of water collection, storage and distribution will be designed to enhance yield and water quality – contaminant loads will be continually reduced - over-reliance on later stage filtration and disinfection is not recommended.
  • Ensure equipment and materials in system are suitable for use
  • Monitor water quality and respond rapidly if changes in water quality are observed (this may be limited to just clarity, colour, smell and taste)
  • Ensure the system devices are always functioning

Such a framework encapsulates a systems approach giving system designers some rules of thumb to guide design. (Rain Harvesting Group, 2014)

 

 (Rain Harvesting Group, 2014)


Managing quality using safeguards

A quality based approach incorporates progressive, sequential and redundant safeguards as control points to improve quality at every step in the rainwater harvesting system.  This could include all or some of the following:

  • Rooftop  -  reduce or eliminate overhanging vegetation and fauna access, eliminate (or seal) materials which may leach hazardous chemicals for example lead from lead flashing, solder, nails, paint on old roofs and gutters
  • Gutters – gutter guards prevent moist vegetation from providing microbial breeding grounds and reduce organic matter entry into water storage
  • Pollutant traps and leaf diverters – reduce organic nutrients into rainwater tank and charged lines and provides mosquito screening for charged lines
  • First Flush – reduce/divert dissolved and fine suspended contaminants including faeces, dust, settled airborne particles (diesel particulates, pesticides etc) and heavy metals (mainly in industrial areas) collecting in rainwater tank. The only treatment points for small suspended particles and dissolved contaminants are the first flush system and sequestration into rainwater tank sediments.
  • Preventing stagnation (by reducing organic matter entry) and or manual or self-draining discharge of charged systems reduces likelihood of stagnant water entry into tank .

Rainwater tank

  • Sealed to prevent animal entry, back flows of water, mosquito entry and algae growth
  • Avoid re-suspension by use of calmed inlet and upturned outlet 100mm from base of tank.
  • Avoid sediment suction by floating off take with collar, placement of submersible pumps on a stand or positioning pump outlet 100mm above base of tank.

This material has been prepared as a result of discussions with the NSW Department of Planning although RHAA is solely responsible for the material. The RHAA provides these as general principles with no implied liability for the advice. In all circumstances you should rely on your own sources for advice that will meet your specific needs. 

 

Last Updated on Friday, 20 November 2015 12:45
 
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