Water Use and Reuse Stream Projects

Soil Aquifer Treatment for horticultural water reuse, Alice Springs, NT

Introduction

Alice Springs is a popular desert town (population 28,000; rainfall 250 mm/yr) that relies on largely non-renewable groundwater reserves from deep aquifers. Opportunities for soil aquifer treatment (SAT) — ie. the process of intermittently infiltrating treated sewage effluent to provide further treatment and store the water in aquifers for reuse — exist in many arid zone communities where soils are free draining, the depth to watertable in the surficial aquifer is relatively deep and waste water is in surplus.

This project is anticipated to be Australia’s first purposefully constructed SAT scheme and was initiated to reduce environmental impacts associated with overflows from the waste water stabilisation ponds to the adjacent Ilparpa Swamp (see Figure 1). Instead, this water will be treated and pumped to the Arid Zone Research Institute (AZRI) where it will be stored in an underground aquifer, and then recovered to use as irrigation supplies for horticulture and viticulture. The AZRI site, also shown in Figure 1, was chosen as the most prospective area for SAT and reuse and an investigation program commenced to characterise the site and assess the potential for SAT.

Objectives/Scope

The principal technical and environmental risks being assessed include:

• excess soil clogging
• surface discharge and waterlogging / salinisation
• environmental water quality objectives
• migration and containment of recharge water
• leaching of minerals from the unsaturated zone
• odour
• insect pests

CSIRO is acting in partnership with the NT Department of Infrastructure, Planning & Environment (DIPE) to address these issues.

Activities

• characterisation of the hydraulic, geochemical and microbiological properties of unsaturated zone from core samples
• field infiltration trials in test basins with mains water to test the infiltration characteristics of the basins and drainage of the subsoil (Figure 2)
• groundwater modelling to predict mound height and migration of the recharge water
• laboratory column studies to determine the effect of different levels of water pretreatment, soil types and water depths on rates of infiltration
• hydrogeochemical studies to assess the sources of groundwater and flow systems within the basin and identify suitable tracers for monitoring the migration of the recharge water
• groundwater sampling, hydrochemical, ‘natural’ tracer and water quality evaluation
• development of monitoring plans for a pilot scale trial.

Key Staff

Peter Dillon, Karen Barry

Partners

• Power and Water Corporation, NT
• Department of Infrastructure, Planning & Environment, NT

Timeline

2003-2006

Links

Water Reuse in the Alice - latest news, media releases, fact sheets, milestones

Figure 1: Location of Alice Springs SAT investigation site at the Arid Zone Research Institute, situated approximately 5 km south of the town centre

Figure 2: Small-scale (6x6m) basin during infiltration test with potable water during period of wetting (left/right) and drying (right/left)