Craig Brown Consulting

Read this first

fra99le — Tue, 05 Oct 2010 11:48:05 +0000

This page contains information about different wastewater system options. It also contains comments by users of those systems. CBC does not recommend any particular system(s) on a general basis (the specific site, situation and circumstances must be considered) and does not take commissions or fees for specifying any wastewater systems.

The real value of this site will come from users posting their experiences, good and bad with each system. Click on the title of each post to read comments and to leave your own.

We encourage you to contribute so that others may learn from your experiences. We shall endeavour to moderate comments as little as possible, to maintain the richness of information, so please be responsible and provide facts and honest opinion and avoid defamation. CBC do not necessarily endorse any of the comments made – our aim is to provide a forum for discussion. One thing we will say: all systems have some limitations and need some management, so negative comments need to be appreciated in this context.

There are a number of posts about different systems on this page, in a draft format to kick-start discussion. Please note that the original posts are the view of CBC only and are general (ie applying to a class of system, not individual systems). Each system has benefits and disbenefits that will differ depending on the site and situation. The complex interactions of these factors cannot be appreciated solely by looking at this page – rather you should engage a wastewater consultant to work through these factors with you.

Septic Tank

fra99le — Mon, 08 Dec 2008 04:08:31 +0000

A correctly-sized septic tank is an effective method of wastewater treatment where there is sufficient suitable land area available for disposal, where further treatment occurs within the soil in aerobic conditions (inside the tank the processes are anaerobic).

Septic tank

Benefits

Proven technology with a wide range of suppliers
Low or no power consumption
Inexpensive
Three-yearly pump-outs only

Drawbacks

Council may be resistant, especially on smaller sections and the system relies upon the soil for completion of treatment
Require sufficient land area and larger setbacks from ground and surface water
Dependent on the (sustained) treatment capacity of the soil

Aerated Wastewater Treatment System

fra99le — Mon, 08 Dec 2008 03:22:48 +0000

An AWTS incorporates a septic tank, but also has a chamber where pumps are used to generate air bubbles. This chamber replaces the aerobic treatment which occurs in the soil in the standard septic tank system, meaning that the effluent produced is already of a higher standard. Whilst primary treated (septic tank) effluent cannot be irrigated using dripper lines, secondary treated effluent, such as from an AWTS, can be irrigated through drippers (note: several other systems also produce secondary, or advanced secondary, treated effluent).

Aerated Wastewater Treatment System

Benefits

Wide range of off-the-peg systems
‘All-in-one’ packaged plants
Relatively economical to purchase
When operating well can produce a high quality effluent
Well accepted by council

Drawbacks

Significant power consumption, expensive operation
Can be noisy
Maintenance can be costly (replacement pumps, etc)
Cope poorly with fluctuations in input (whether up or down) so less well suited to holiday homes, etc

Media filters/reactors

fra99le — Mon, 08 Dec 2008 03:15:45 +0000

These systems use a media filter chamber to contain the aerobic treatment process. The media can include sand/gravel, peat and textiles amongst other things. These systems achieve secondary or advanced secondary treatment and are well suited to tertiary treatment if required or desired (additional disinfection by chlorine or UV).

Media filter 1

Media filter 2

Benefits

Some off-the-peg systems available
Cope better with fluctuations in input
Produce a high quality effluent
Some well accepted by council

Drawbacks

Can be more expensive
Construction can be tricky
Can under some configurations (eg recirculating) achieve high levels of nutrient reduction (important for sensitive receiving environments like waterways)
If they fail it can be expensive and difficult to replace the media
Council may require extensive monitoring of some designs (eg peat beds)

Vermicomposting Units/Humus Ecology Filters

fra99le — Mon, 08 Dec 2008 02:27:03 +0000

These systems act a little like compost heaps where solid wastes collect and are degraded by the resident worm population whilst the liquids filter through to a collection area below. Generally the level of treatment is of a high primary standard, but some systems achieve a secondary level of treatment.

Vermicomposting system

Benefits

Some systems well accepted by council (other systems may not be)
Probably cope better than other systems with a garbage grinder and even some chemical use
Produce a reasonable quality effluent
Low (or even no) power consumption
Can be quite compact units
Can be used with drip irrigation (some systems)

Drawbacks

Poor nutrient reduction (nitrogen/phosphorous) (may be OK or even a benefit if water is used appropriately in a low-sensitivity receiving environment)