Recharge systems for protecting and enhancing groundwate

TOPIC 1
Injection well issues, aquifer storage and recovery / Recharge systems 153
Environment Protection Authority (EPA) requirements. The ASR wells are equipped with extraction pumps and
recharge (injection) facilities. There are five observation wells used for monitoring the effects of the ASR operation.
Three are located around the Parafield facility and two are placed 900 m to the south one in the overlying T1
aquifer and one in the T2 aquifer.
The extraction pumps are variable speed drive submersible units each with a nominal capacity of 4.3 ML/d, giving
a total ASR delivery capacity of 8.6 ML/d. The recharge capacity of each well is nominally 3.0 ML /d, giving a total
of 6.0 ML/d recharge capacity. The well pumps and recharge facilities are operated automatically by the control system
which can be accessed by telemetry from the Salisbury Council offices. Both wells operate together either in the
recharge mode or in delivery mode or are inactive at any one time. Individual wells can be taken out of service. All
cleansed water flows in excess of the pipeline demand rate are recharged to the ASR wells. When there is no water
flow from the reedbed the full demand is supplied from the ASR wellfield.
It is infeasible to extract 100% of the volume of water that has recharged the aquifer and maintain acceptable salinity.
This is because of mixing of the recharged water and the native groundwater around the edges of the recharge
plume. Hence it is assumed that only 80% of the recharged water can be extracted at an acceptable salinity. Flow
controllers are located on the recharge connections to avoid over pressurising the aquifer during recharge. The
flow controller setting at the well head is based on the hydraulic characteristics of the completed well. At times the
wells suffer clogging from particulates and biomass build-up. Each well has a purging system for clearing of the
clogging material. This is discharged to the in-stream basin via 150 mm diameter purge water pipes. Flow, level and
salinity data are collected from the ASR operating and observation wells by the control system as part of the ASR
Management Plan required by the Department of Water Land Biodiversity and Conservation (DWLBC) and the
Northern Adelaide – Barossa Catchment Water Management Board (NABCWMB). Due to this project Australia’s
largest wool processing company (G.H. Michell & Sons) receives water with a salinity (TDS) of less than 250 mg / L,
which is significantly lower than the salinity of mains water derived in dry years mostly from the River Murray
(which frequently exceeds 400 mg/L).
Operational results
Stormwater harvesting and wetland
Stormwater could be selected for harvesting and poorer quality water was bypassed from the ASR system. Table 1
indicates the quality of water in the drain and in the discharge from the wetland. The data indicate no parameters
exceed the national guideline for irrigation water quality, and most parameters for wetland-treated stormwater compare
favourably with existing drinking water supplies.
Table 1. Contaminant reduction through selection of water from Parafield Drain for harvesting
and treatment in the Parafield Wetlands*
PARAMETER
Suite Taken Parafield drain median Reedbed median Percent reduction
General
Conductivity (µS/cm) 457 191 58 #
Total Dissolved Solids 250 100 60 #
pH 7.70 7.00 9
suspended solids 13.00 3.00 77
total organic carbon 8.90 4.40 51
turbidity 8.10 1.70 79
10 – 16 June 2005, Berlin ■ 5th International Symposium ■ AQUIFER RECHARGE ■ ISMAR 2005