Applied research on on-site and small community wastewater treatment and effluent disposal in Australasia

Applied research on on-site and small community wastewater
treatment and effluent disposal in Australasia

The writer recognised in the early 1970s that there was a need to focus on improvements to on-site wastewater treatment technology, effluent disposal and
associated aspects of water pollution control. At the time there was considerable potential for applied research in the development of improved treatment and effluent
disposal technologies since some 16 to 20% of the populations in New Zealand and Australia relied on on-site or decentralised wastewater treatment and effluent
disposal.

This thesis covers applied research projects undertaken in New Zealand, during the period 1974-1990, and in Queensland from 1992 to the present day. These experiences have been written up in the form of a guide to the dissertation (contained within the initial three chapters) and eight technical portfolios.

During University of Auckland post-graduate studies in 1974 the writer reviewed the unique problems of widely fluctuating wastewater loads from coastal and lakeside
communities, camping grounds and resort areas. The review evaluated improvements to septic tanks, alternative effluent disposal systems, upflow pebble filters, lagoons, rotating biological discs, and composting toilets. Solutions for handling fluctuating wastewater loads have been further extended.

Due to failed effluent trenches in Northland New Zealand, associated mainly with problem clay type soils, the writer undertook experimental work on the determination of soil permeability by field and laboratory techniques, investigated soil properties impacting on effluent disposal and researched alternative methods of on-site effluent treatment during the period 1976-1979. This included experimental work on evapotranspiration (ET) systems and the compilation of selected plants, shrubs and trees for planting within ET systems in the Northland and Auckland
areas. This work has been directly applied to much of Queensland.

An experimental Clivus Type domestic composting toilet was established in 1976 and monitored in Kerikeri, Northland, New Zealand. The design of associated greywater and disposal systems consequently took place in New Zealand and
Queensland.

The then Queensland Department of Primary Industries (Water Resources) identified the need to develop alternative wastewater treatment technologies in the early 1990s.
The writer set up an Artificial Wetlands Research and Advisory Committee to develop this technology within the range of climatic conditions in Queensland. This
thesis focuses on the design rationale, nitrification and de-nitrification of effluent in reed/gravel beds or sub-surface wetlands.

A postal survey of Australian effluent disposal systems was undertaken during the period 2000-2001. This showed that a broad range of disposal techniques were being used.

A range of innovative (more non-conventional) treatment and disposal systems have been presented for use in Australasia.

Raised sand mounds for effluent treatment have not been used on a wide spread basis in New Zealand and much of Australia. The performance of an existing sand mound, the design based on AS/NZS 1547:2000, located in Morayfield, Queensland has been assessed.

A survey of deep shaft disposal was undertaken over much of the North Island of New Zealand over the period 1976-1977. This unique method of post-treatment and effluent disposal has merit in locations where shallow trenching is not appropriate and in deeper more permeable soils, that are clear of the groundwater.

Experimental work on the use of lime and solar salt brines with seawater and magnesium salts, for treating municipal wastewater and a range of process waters was undertaken in New Zealand over the period 1984-1986. This work was
extended as a joint research project with the Queensland University of Technology in the mid-2000s.

This thesis reflects on past experimental and innovative work on on-site wastewater treatment and effluent disposal in Australasia and it recommends improvements
and/or alternative technologies that can used to achieve higher standards of treatment. It consists of three chapters and eight portfolios covering separate topics.
The connections between the chapters and the portfolios are shown in Figure 2a of Chapter 2. The conclusions drawn from each portfolio are collated and summarized in Chapter 3.

Copies of selected papers and technical reports are compiled in a separate Volume 2.