Martin’s House – Greywater in a new home for irrigation of fruit trees

Most fruit trees and vegetables are suitable with subsurface drip irrigation not exceeding 10mm or 10 litres/sqm per day where grey water friendly soaps and detergents are used. Greywater to fruit trees and many perennials avoids the need to use energy intensive mains water!!

I’ve installed a very simple greywater diversion and reuse system at my home for irrigation of fruit trees. It takes the greywater from 2 washing machines in our shared laundry and diverts it to a subsurface piped trench running the length of the front garden bed containing pomegranites (as shown in the photograph).

The greywater diverter unit is an original first approved unit in Western Australia developed by Jim Bertrand. It has a simple mesh filter that can be manually removed and washed under the outdoor garden tap when getting clogged with lint and other matter. It can divert greywater to sewer via a hand operated valve in winter or as required. Very simple and effective and low cost.

 

Here is some information on its design rationale:

“The average house (based on three persons per house) produces 523L of greywater everyday. This equates to approximately 113L of greywater per person per day. Of this 47 litres is produced in the laundry and 66 litres from the bathroom (Loh & Coghlan, 2003).” (Page 7 in Dept Health, Code of Practice Greywater, 2010)

Will be less now due to improvements in efficiency of water fixtures and WELS rating scheme and even moreso at WGV with rigorous minimum standards imposed by Landcorp.

(Page 26 in Dept Health, Code of Practice Greywater, 2010)

 

Martin’s House – Lot 4 common facilities:

Laundry only = 280 x 5 persons (1brm apartment + 2brm apartment) = 1,400 litres/week (or 200 litres/day)(outdoor shower as runoff to garden or to sewer)

Laundry + outdoor shower = 1,400 + 420 x 2 =2,240 litres/week (or 200+120=320litres/day)

Design Irrigation Rate (DIR) for sand = 10 mm/day

Note: Soil categories and DIR are modified from AS 1547.
* Up to 10 mm/day DIR is allowed for sandy soils in sewered areas of the Swan Coastal Plain
(Table 7, Page 35 footnote in Dept Health, Code of Practice Greywater, 2010 v2)

Area of land needed = 200/10 OR 320/10 = 20 or 32 sqm

Method of irrigation to be subsoil piped trench as per AS1547:2012, Table L1.

A = surface area of the trench in m2 (i.e. the sides below the invert of the distribution pipe and base of the trench per lineal metre).

A = [0.25m (side) + 0.30m (bottom) + 0.25m (side)] x 1m = 0.80m²/lineal metre.

Trench dimensions determined from the relationship:

L = Q / (DLR*W) (AS1547:2012, p144) where:
L = length in m
Q = design daily flow in L/day
DLR = design loading rate in mm/d = 50mm/d (from Table L1)
W = width in m
L = (200 or 320)/(50*0.3) = 13 metres or 21 metres.

Therefore, 13 metres for laundry greywater only (outdoor shower to own garden bed).
Construction as per Figure L1 on page 151.

Let me give you some general information on greywater reuse

Greywater can be considered to be a separate stream of wastewater especially where blackwater will be directed to separate collection and treatment or where dry toilets are implemented. The greywater can be diverted to a ‘fit-for- purpose’ application such as landscape irrigation for woodlots or food production. Greywater can also have a higher level of treatment so that it can be used indoors, for example, toilet flushing, without causing staining or odours. Greywater recycling then becomes a separate activity to help ‘close the cycle’.

Approved greywater systems in Australia are usually classified into Greywater Diversion Devices (GDD), having only coarse filtration, and Greywater Treatment Systems (GTS) where treatment to a higher standard may include microfiltration and disinfection. A new Australian Standard for the design of greywater systems using this classification system is imminent: AS1546.4:2016 On-site domestic wastewater treatment units – Part 4: Domestic greywater treatment systems.