T McGrath, N Shishkina, R Theobald, C Rodrigues
Publication Date (Web): 23 March 2016

Aerobic Treatment Units (ATU) and Greywater Treatment Systems (GTS) are electrically driven onsite wastewater treatment systems (OWTS) designed to treat wastewater to secondary effluent quality standards.

ATU are designed to treat wastewater – both blackwater and greywater – either wholly or partially, from all areas of the house by aerobic means. All ATU incorporate the following processes: primary sedimentation, biological treatment, secondary sedimentation, and, usually, disinfection.

GTS are designed to treat greywater only and typically consist of the following treatment processes: filtration or screening, biological treatment and disinfection.

Despite the usefulness of OWTS, they can present a risk to human health and the environment when they fail or are used inappropriately. This is due to the contaminants that are present and the nature of the wastewater they treat. Therefore, maintenance of the electrical, mechanical and chemical components of these OWTS is important for ensuring their consistent and reliable operation to the required standards.

In Western Australia (WA), the Department of Health Western Australia (DOHWA) approves each system design prior to system sale and installation, and set outs the regulatory requirements for the maintenance of OWTS as well as when and how maintenance is to occur.

All service personnel must be accredited by either the DOHWA or the system manufacturer; once accredited, they must also abide by the DOHWA-issued Conditions of Approval. Once the basic product approvals from the DOHWA are in place, the management of individual domestic systems is controlled by local government Environmental Health Officers (EHO). The guidelines and regulations provide a framework that assists EHO in overseeing the management of domestic systems. Management includes approving the installation of systems, issuing permits to use systems and enforcing the maintenance requirements.

This paper reviews the maintenance requirements for ATU and GTS in WA and provides recommendations for the proposed changes in guidelines and regulations. State and National guidelines were reviewed and information from industry and regulators was obtained through surveys. Surveys were sent to those most heavily involved in the domestic wastewater treatment systems industry to give the opportunity to express any dissatisfaction, opinions and recommendations and to allow practical information to be gathered.

Two computer-based surveys were developed, one aimed at local government EHO, and another aimed at manufacturers and service personnel. A total of 40 responses to the surveys were received. Of these, 24 came from EHO and 16 from manufacturers and service personnel. The survey responses suggested that industry personnel were, generally, content with the current maintenance arrangements, however they also allowed several problem areas to be identified.

This paper identifies and discusses areas of the guidelines requiring improvements, based primarily on concerns raised by those working in the industry. The implementation of the recommendations provided could address industry concerns, ensure the delivery of effluent water quality standards in a reliable manner during the life of the systems, encourage more innovative system design and assist development of the Code of Practice for Onsite Sewage Management, which is currently in the draft stage.

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