INTRODUCTION

Where a property has no access to a main sewer line, as in rural or remote areas, there is a need for an alternative system to deal with household wastewater. While septic tanks have traditionally been the most common option for residential applications and still have a place in the market, concerns about their environmental impact has the industry looking towards more effective treatment options. Offering higher quality effluent, advanced aerated systems have gained traction as they enable water to be safely reused for irrigation purposes.

The sustainable treatment and reuse of wastewater is critical for Australia’s future. As recently as 2019, the nation experienced its driest year on record, with significant deficiencies in rainfall in regions throughout the country continuing into the following years.1 The need to save, recycle and reuse water is an ongoing concern for many households and local communities.

Against this backdrop, the specification of an onsite wastewater system takes on even greater importance as it allows households to save and safely reuse significant amounts of water every year, alleviating pressure on public water supplies. There are many companies offering residential wastewater treatment systems, but not all solutions are created equal. Site conditions, owner requirements, and council regulations all come into play when specifying an effective solution for any onsite application.

Specifiers must also consider the impact of the new AS/NZ1546.3:2017 On-site Domestic Wastewater Treatment Units – Secondary Treatment Systems. Recent changes to the standard require aerated wastewater systems to meet increasingly stringent capacity and performance requirements. Consequently, existing systems must undergo testing and certification under the new standard before they can be approved for use in any State or Territory.
This whitepaper looks at the specification of residential wastewater systems with a focus on advanced aerated wastewater systems, and how they compare to traditional septic tanks. We also look at the impact of the new AS/NZ1546.3:2017 and other relevant factors when choosing an aerated wastewater system for your next project.

 

WHAT IS A WASTEWATER SYSTEM?

A residential wastewater system allows for the onsite treatment of wastewater (that is produced from the water used in a home) and safely dispose of it. The two main types of onsite wastewater water systems are septic tanks and aerated wastewater systems.
Septic tanks have traditionally been the popular choice for onsite wastewater treatment. A septic tank is an underground chamber through which domestic wastewater flows for basic treatment. Septic tanks are generally made of concrete, fiberglass or plastic and rely on the settling of solids and anaerobic processes as the main treatments for wastewater.
Aerated wastewater systems are considered the most effective for residential onsite wastewater treatment. Comprised of a system of mechanical pumps and compartments, such systems utilise the aeration process, in which wastewater undergoes several treatments as described below:

The Aeration Process

1. Solids settle to the bottom of the first compartment and scum floats to the top, resulting in partial clarification of the wastewater.
2. The partially clarified wastewater flows to the second compartment in which a pump is used to aerate the wastewater. Proper aeration promotes microbial growth in the wastewater, and assists bacteria to further break down the incoming organic pollutants.
3. The third compartment allows for the further settling of solids.
4. In the fourth compartment, wastewater is subject to a disinfection process, often through chlorination.
5. In the final stage, the treated effluent (treated to a secondary standard) is pumped away for surface or subsurface irrigation or otherwise safely disposed of.

Advanced aerated systems are available that utilise membrane filters that produce higher quality effluent and use UV disinfection processes rather than chlorination. Advanced systems have two clear advantages. First, membrane filtration can filter out most particles, nutrients and diseases, producing a very clear, higher quality effluent. Second, UV disinfection enables wastewater to be treated to a higher standard, while ensuring it is free from chlorine, thus making it more suitable for irrigation purposes.

 

 

Read the rest of the Whitepaper here: https://www.architectureanddesign.com.au/resources/whitepapers/treat-recycle-and-reuse