Newsletter and Technical Publications
<Proceedings of the International Symposium on Efficient Water Use in Urban
Areas
- Innovative Ways of Finding Water for Cities ->
D. Session 4: Augmentation of Groundwater Resources
through Aquifer Recharge
Moderator: Dr. Bruce E. Jank, Canadian Global Environmental Technologies,
Canada
Rapporteur: Dr. John Bwalya Mwanza, Project Manager, Barbados Water Authority
Presenters:
(1) Prof. Peter Fox, Arizona State University, USA
(2) Prof. Takashi Asano, University of California at Davis, USA
(3) Dr. Peter James Dillon, Centre for Groundwater Studies and CSIRO Land and
Water, Australia
Three presentations were made dealing with advantages, regulatory
perspectives, technologies, risks and implementation issues associated with
aquifer recharge.
Paper 1: “Advantages of Aquifer Recharge for a Sustainable Water Supply”
by Prof. Peter Fox
Key Points Presented:
- Wastewater reuse is a water resource issue which should be incorporated in
water resources management planning.
- Water banking is an important water resources management strategy.
Criteria should be established to determine who has the rights to the “banked”
water.
- There is a need to establish regulations or controls for water quality
used in recharge schemes.
- Decentralised treatment with subsequent aquifer recharge in
strategically located recharge sites represents a cost-effective option for
mega-city systems. The decentralised treatment/recharge sites should be
selected to effectively control the water table.
- Natural watercourses or flood plains can be used to reduce water transport
costs.
Issues to be Evaluated:
- What is the time required to recharge an aquifer?
- What is the cost of maintaining/cleaning direct injection wells?
- What parameters should be used, and what are the specific limits for each
parameter, in establishing regulations and water quality standards for
aquifer recharge?
- How should the impact of aquifer recharge on existing potable water wells
be measured?
- Can groundwater recharge systems be used to replace surface water storage
impoundment?
Paper 2: “Groundwater Recharge with Reclaimed Municipal Wastewater –
Regulatory Perspectives,” by Prof. Takashi Asano
Key Points Presented:
- The level of nitrogen in the aquifer recharge water must be controlled and
monitored. The recommended limit for total nitrogen is 10 mg/l.
- The costs for pollution control should be separated from water reclamation
costs. It is recommended that secondary treatment costs be allocated to
pollution control, with the tertiary treatment costs allocated to water
reclamation.
- Monitoring programmes are required for aquifer recharge programmes.
Parameters used in California for regulatory purposes are TOC, Total
Coliform Count, TDS and TN.
Additional Questions Raised:
- Have there been any incidents of health issues associated with aquifer
recharge? Based on health studies conducted to date, there have been no
epidemiological incidents reported.
- What is the cost per m3 of water recovered from aquifer recharge schemes?
While this is generally expensive, it needs to be compared with other
options on a case-by-case basis.
- Are there any problems associated with the accumulation of recharge water
in the aquifer? Any potential problems can be addressed by creating steady
state conditions, where withdrawal is balanced against recharge.
- What are the issues associated with public acceptance of aquifer recharge?
It is important that detention time in the aquifer be estimated to ensure
public acceptance of the product.
Issues to be Evaluated:
- Hydrogeologic conditions must be established for each site.
- Parameters to be monitored need to be established.
Paper 3: “Aquifer Storage and Recovery in Urban Areas – Technology,
Risks and Implementation Issues,” by Dr. Peter James Dillon
Key Points Presented:
- An aquifer recharge option was described, involving a single well for
recharge and subsequent withdrawal.
- It was noted that groundwater recharge occurs below all irrigation
operations.
- Both reversible and irreversible clogging of injection wells have been
noted to occur, but this can be addressed by redevelopment of the well at
various intervals.
- The use of a separate injection well and a separate withdrawal well
(appropriately spaced to take advantage of the aquifer cleaning capacity)
can be used to substantially improve the quality of injected water.
- Aquifer storage capacity needs to be available for aquifer recharge to be
successful.
- It was suggested that it is more appropriate to use nutrients for
irrigation of agricultural crops than to release them into the atmosphere
during treatment.
- Acceptance of aquifer recharge schemes involves proper presentations to
the community.
- It is proposed that developmental maps be provided to local authorities
regarding potential areas of recovery/recharge.
Issues to be Evaluated:
- Do pathogens injected into the aquifer survive or grow?
- Does the injected water induce growth of opportunistic or indigenous
pathogens?
- For groundwater recharge through irrigation schemes, are pesticides and
herbicides a potential problem?
- Sulphate reducers in aquifers should be monitored because of the potential
for aquifer clogging.
Session Recommendations:
- Where aquifer recharge is being considered, an appropriate
regulatory framework should be established.
- Policies should be established for the banking of water, to
encourage the safe and beneficial application of aquifer recharge.
- Water and wastewater treatment plants should be located in areas
where the subsurface geology is appropriate for effective aquifer
recharge.
- Decentralised wastewater treatment plants should be located adjacent
to aquifer recharge sites, thereby ensuring minimal impact on the
groundwater table.
- Further research is needed to determine appropriate and safe methods
of water injection and withdrawal, to ensure inactivation of
pathogens.
- Where possible, excess treatment plant capacity should be used to
provide treatment for aquifer recharge.
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