Rainwater collection for grey water use

Introduction

This GPI involves the installation of water capture systems on the rooftops of port buildings to capture rain.  This will then be stored in tanks for reuse in greywater applications such as flushing toilets, washing down the wharf / yard, washing equipment / cars, etc. The tanks can also be used as an emergency source of water for a first response to firefighting. 

Drivers

This green port initiative will reduce water consumption, thereby lowering the environmental impact of the port and the running costs from water purchase. The main measure of success will be a noticeable reduction in the amount of water being consumed every month. 

Approach

1.  The potential amount of water that could be captured from each of the main buildings at the port was assessed. The assessment showed that the amount of water that could be captured annually from each building ranges from about 1.1M litres (SPA Administration Building) to 9.3M litres (Cable Warehouse). 

2.  The range of commercially available water tanks was assessed. Tanks readily available in Samoa range in size from 1,000 to 10,000 litres, where a 5,000 litre tank provides sufficient storage for approximately 380 toilet flushes

3.  The main uses at the port were assumed to be:

    1. Toilet flushing in the SPA Administration Building (requiring additional plumbing to connect water supply to toilets).

    2. Toilet flushing/car washing in the SPA Clubhouse (requiring additional plumbing to connect water supply to toilets).

    3. Washing down of equipment at the new maintenance workshop location.

    4. Washing down the wharf.

4.  Water tanks were assumed to be required for the SPA Administration Building (1x 5000L), SPA Clubhouse (1x 5000L), Shed 2 (2x 5,000L) and at the Cable Warehouse (2x 5000L).

5.  The proposed locations for the water tanks were:

Two (2) tanks located at the south-east corner of the Cable Warehouse.  The water collected here can be used for washing down the wharf / yard.

Two (2) tanks located at the northern corner of Shed 2.  The water collected here can be used for equipment washdown purposes.

One (1) tank located at eastern corner of SPA Admin Building, and one (1) tank located at southern end of SPA Clubhouse.  The water collected here can be used for watering gardens and for flushing toilets.  Noted that additional header tanks and plumbing will be required.

6.  SPA confirmed the number of tanks and suitable locations for tanks to be installed.

7.  SPA then engaged a contractor to supply and install tanks (including the rainwater harvesting system, and water distribution system).

Cost and timeframe

Upon completion of this initiative, it is calculated that the total cost of the GPI, including the payments to the contracting company, were approximately $80,000 WST. The predicted cost for this initiative was $24,000 USD (which is approximately $66,000 USD).

The timeframe that was given to the Contractor was five (5) weeks for all the works, but this was exceeded due to variations that were requested by SPA (i.e., some of the buildings needed additional infrastructure, including the installation of gutters on the roofs).

Maintenance and monitoring

Several monitoring and maintenance activities need to be taken for this initiative to be successful, some of which will be implemented later. Those in place now include:

    1. Collection System - Roof surface and gutters are to be cleaned and cleared of excessive debris, and inspections are to be conducted twice a month to ensure water flows and clear drains.

    2. Storage Tanks - Inspections of tanks for cracks of leakages will be annually carried out. The regularly maintenance of filters ensures the sediment accrual will be minimal at the bottom of the tanks.

    3. Overflows - To be visually inspect one a month to ensure they are clear of debris.

    4. Water Level Indicator - There is an indicator (ball) placed in the tanks to indicate when the water level is low and for the water tanks / pumps to extract water from the main supply (Samoa Water Authority). This will stop the pumps from breaking down when the tanks are empty.

    5. Finance Monitoring - The Finance Division will provide a report on the usage of water and electricity for this initiative monthly.