‘This is a wonderful book that should be on the desk of every architect and planner. It shows how

Box 13 Water and Sewage Management
Sarah West
In today’s society, nearly every source of water (rainwater, stormwater, snow, floodwaters, 
groundwater, rivers, lakes, estuaries, wetlands, the oceans, sewage, dams or industrial effluent) 
is compartmentalized and controlled by different organizations. This has invariably resulted in 
water from one source polluting another, such as stormwater polluting rivers, or sewage pol
-
luting the ocean. Urban water supply and wastewater management schemes in industrialized 
countries have followed the centralized engineering design established in London and Paris in 
the late 1800s to protect the public from cholera and other waterborne diseases.
Piping sewage and stormwater away from homes to distant treatment facilities before discharg-
ing it to rivers and the sea has protected public health and possibly increased the longevity of 
many people. However, the design has also affected the environment and degraded the health of 
aquatic life and ecosystems.
1
Over time the impact has increased in different parts of the world, 
as more industrial wastes and household pollutants have been added to sewage. Household 
pollutants primarily occur in the form of pharmaceuticals, hormones, personal care products 
and cleaning agents.
2
Pollutants in waterways can accumulate and alter the physiology of fish 
and other aquatic animals, and may affect the health of humans who eat the seafood.
Today, as waterborne diseases have been largely eliminated in developed nations and clean 
water is in short supply in many countries, we face the challenge of improving the health of 
waterways and making better use of the water we have. Integrated water management and 
recycling at the local community and sub-catchment scale can provide a number of long-term 
benefits, including increased security of water supply and cleaner waterways. Decentralized 
or distributed water systems are able to efficiently integrate a range of local water sources, 
including treated sewage effluent, to optimize the variations in seasonal water supplies. 
The values and aims that underpin decentralized, integrated water and wastewater manage
-
ment and recycling are resource efficiency, resource maximization, resource recovery, closing 
the nutrient cycle, closing the water cycle and closing the food loop.
3
To minimize capital and operational costs, water needs to be captured, stored, used and recycled 
near its point of origin
(approximately 90 per cent of the capital cost of conventional central-
ized water and sewerage systems is in trenching and installing large pipes over long distances).
Current Positive Developments in water management are decentralized household-, cluster- or 
community-scale integrated water and sewerage systems that incorporate a range of tech-
nologies and water qualities ‘fit for different purposes’. The design and technologies used will 
depend on a range of factors, such as local air quality, environmental conditions, cost, ease of 
management, cultural factors and recycling opportunities. For example, options for household 
on-site water collection and sewage treatment and recycling systems include:
•
Rainwater tanks for drinking, cooking and showering with supplementary water from 
the reticulated (piped) town supply; a ‘wet composting’ (vermiculture) system to treat 
blackwater from the toilet; greywater treated and recycled for toilet flushing, garden 
irrigation and use in the washing machine.
•
Spring, well, dam or river water for drinking, cooking and bathing; rainwater tank 
for supplementary water supplies; a dry composting toilet; greywater treatment and 
recycling to garden irrigation.
•
Town water supplies for drinking, cooking and hand basins; rainwater into the hot water 
system for showering and use in the laundry; combined sewage (black and greywater) 
treated and recycled for toilet flushing and garden irrigation.
•
Cluster or neighbourhood sewerage systems incorporating ‘effluent sewers’ with small 
diameter watertight pipes, and local sewage treatment and recycling schemes.

---

291
Boxes
The term ‘effluent sewer’ is used for a system where the household sewage solids separate 
from the sewage water and settle out in a tank on each lot. The clarified effluent in the tank 
then either gravitates or is pumped away through a network of watertight pipes to a local 
sewage treatment plant.
4
When compared to a conventional gravity sewerage system, the 
benefits of a decentralized watertight effluent sewerage system are:
• 
No infiltration of stormwater into the sewers
• 
No need for sewage (plus stormwater) to bypass the treatment plant in wet weather 
nor be discharged directly to the waterway
• 
No escape of raw sewage from leaky pipes into the surrounding soil and groundwater
• 
No sewer-overflow valves that discharge raw sewage into rivers
• 
Small diameter pipes do not need to be trenched
• 
Flexible pipes can go around rocks, structures, trees and cultural sites
• 
Pipes travel short distances within the community area
• 
As the pipes carry primary treated effluent, and not raw sewage, there is less 
detrimental impact if a pipe is accidentally broken
• 
Effluent pumps use minimal electricity, thereby minimizing the generation of greenhouse 
gases, especially when local sustainable energy is used
• 
All sewage is treated and beneficially recycled
The treatment component of an effluent sewerage system is a combination of primary treat
-
ment (screening and settling) in a household tank and secondary treatment (biological diges-
tion) at the community sewage treatment plant. The benefits of retaining most of the sewage 
solids in the household tank are: 
• 
The pipes are small because they are not transporting solids
• 
There is very little likelihood of pipes becoming clogged
• 
The small pipes are relatively quick and inexpensive to install
• 
The secondary treatment plant is smaller and cheaper to build and operate, because it 
does not need to process the majority of the solids
However, household interceptor tanks do need to be de-sludged every 5 to 15 years, depend
-
ing on the size and characteristics of the wastewater. Through the use of remote monitoring 
(telemetry), household and decentralized systems can be efficiently and cost-effectively oper
-
ated and maintained by a centralized management authority.
5
The design of a local secondary sewage treatment plant for a cluster of homes, neighbourhood 
or subdivision is based on the reuse opportunities in the surrounding area. Treated effluent can 
be piped back to homes for garden watering, toilet flushing and use in the washing machine; to 
community or council land for use on sports fields, golf courses, parks, gardens, road verges, 
race courses and airfields; to agricultural land for growing pasture, fodder crops, orchards, turf, 
bamboo, essential oils, herbs, flowers and woodlots; or to mining and industrial sites. Once 
the recycling opportunities have been identified or created, the sewage treatment system can 
be designed to achieve the required effluent quality. Effluent recycling opportunities can be 
created that generate a product for consumption or sale to the community.
Where there are insufficient effluent recycling opportunities in winter or wet weather, the 
excess can be stored, transported elsewhere or, depending on the soil type, dispersed through 
the soil profile to groundwater where it later becomes beneficial baseflow in the adjacent 
rivers. Final effluent from ‘best practice’ decentralized sewage treatment systems, such as 
textile filters, sand filters and reed-beds, are safely disposed of through the soil in winter in 
New Zealand and the US.
6
Through decentralized local water collection and sewage treatment and recycling systems 
that are designed to meet the needs of the local community and catchment, we can protect 
human and aquatic life and live in better balance with our environment.

---

Positive Development
292