Improving the performance of septic tank soil absorption systems : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology at Massey University
type: CreativeWork
description: This thesis is primarily a literature review of research and information about septic tank soil absorption systems and their combined performance as on-site sewage treatment systems. The purpose of the review is to analyse the functions of the tank and the soil absorption area and assess how aspects of their design affect their overall performance. Design variations that optimise septic tank soil absorption system performance have been determined so that they can be applied in New Zealand. An assessment of New Zealand septic tank soil absorption systems with regard to their treatment capabilities shows that they are designed to fail. That is, the tanks are designed to produce a poor quality effluent, and the absorption areas are designed to produce saturated conditions so that contaminants in the effluent are transported to groundwater. Inadequate systems are installed and used because there has been little New Zealand research into the environmental and public health effects of their use and how these effects could be reduced, and there has been limited application of knowledge gained from overseas research. Septic tank design features that optimise wastewater treatment are dual or multi-chambered tanks, outlet tees, outlet baffles, anaerobic filters, and large sludge storage volumes. These features improve the physical processes of sedimentation and separation, the biological process of anaerobic decomposition, and provide storage for accumulated sludge and scum. Incorporating these features can achieve consistent, significant biochemical oxygen demand and suspended solids reductions and assist in retaining pathogenic organisms and nitrogen in the sludge at the bottom of the tank. Dual or multi-chambered tanks, outlet tees, and outlet baffles are effective because wastewater short-circuiting is avoided or decreased and sludge is retained in the tank. Anaerobic filters provide effective treatment of low strength wastewater and are insensitive to variable loading ra…
abstract: This thesis is primarily a literature review of research and information about septic tank soil absorption systems and their combined performance as on-site sewage treatment systems. The purpose of the review is to analyse the functions of the tank and the soil absorption area and assess how aspects of their design affect their overall performance. Design variations that optimise septic tank soil absorption system performance have been determined so that they can be applied in New Zealand. An assessment of New Zealand septic tank soil absorption systems with regard to their treatment capabilities shows that they are designed to fail. That is, the tanks are designed to produce a poor quality effluent, and the absorption areas are designed to produce saturated conditions so that contaminants in the effluent are transported to groundwater. Inadequate systems are installed and used because there has been little New Zealand research into the environmental and public health effects of their use and how these effects could be reduced, and there has been limited application of knowledge gained from overseas research. Septic tank design features that optimise wastewater treatment are dual or multi-chambered tanks, outlet tees, outlet baffles, anaerobic filters, and large sludge storage volumes. These features improve the physical processes of sedimentation and separation, the biological process of anaerobic decomposition, and provide storage for accumulated sludge and scum. Incorporating these features can achieve consistent, significant biochemical oxygen demand and suspended solids reductions and assist in retaining pathogenic organisms and nitrogen in the sludge at the bottom of the tank. Dual or multi-chambered tanks, outlet tees, and outlet baffles are effective because wastewater short-circuiting is avoided or decreased and sludge is retained in the tank. Anaerobic filters provide effective treatment of low strength wastewater and are insensitive to variable loading ra…
author: Forsyth, Kirsten Anne
keywords: Septic tanks, Sewage disposal plants
date published: 1996
date modified: 2026-07-27T20:17:21Z
provider: Massey University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Massey University