Ground Water Recharge Using Waters of Impaired Quality (1994) / Chapter Skim
Currently Skimming:
1 An Introduction to Artificial Recharge
1 An Introduction to Artificial Recharge
Pages 12-34
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 12... ...
. This report discusses three types of source waters having very different characteristics treated municipal wastewater, stoTmwater runoff, and irrigation retuIn flow that have been proposed for use in artificial recharge.
|
From page 13... ...
Thus when recharge water is withdrawn later for another purpose, it may require some degree of posttreatment, depending on its intended use. Taking a systems perspective that encompasses all steps from pretreatment, through recharge, through transformation and transport, to extraction, this report assesses the issues and uncertainties associated with the artificial recharge of ground water using source waters of unpaired quality.
|
From page 14... ...
Ground water in the shallow geologic units containing the water table is called unconfined because the water is more or less in direct contact with the atmosphere. Recharge to a water table aquifer occurs wherever rainfall or surface water infiltrates downward through the soil to the water table.
|
From page 15... ...
UJ LL ~D ~ ce )
|
From page 16... ...
An overview of sources of water, treatment options, recharge systems, recovery techniques, and uses of the water after recovery is given in Table 1.1. Surface Infiltration Systems Surface infiltration systems designed to provide artificial recharge of ground water require permeable soils (sandy loams, sands, gravels)
|
From page 17... ...
Disinfection Advanced (removal of metals, nitrogen, phosphorus, total organic carbon, and total dissolved solids)
|
From page 18... ...
In-channel and off-channel infiltration systems are common in California, where there are a large number of successful recharge projects. The range of infiltration rates (i.e., the rate water drains into the ground when a basin is flooded)
|
From page 19... ...
AN INTRODUCTION TO ARTIFICIAL RECHARGE FIGURE 1.3 Infiltration basin near Palm Springs, California, using Colorado River water. The windmills are for power generation.
|
From page 20... ...
To achieve optimal infiltration rates, a number of features need to be considered in the design process, including clogging, water depth, and ground water level. Clogging A major operational feature of infiltration systems for artificial recharge of ground water is soil clogging caused by to accumulation of suspended solids on the bottom and banks of the infiltration facility as Hey settle or are strained out on the soil surface.
|
From page 21... ...
As clogging material continues to accumulate on the bottom and banks of the infiltration facilities, it eventually reduces infiltration rates so much that it should be removed. For treated municipal wastewater this process may have to be repeated every 1 or 2 years if the municipal wastewater has had adequate pretreatment and clarification (suspended solids contents less than 10 mg/1~.
|
From page 22... ...
Where infiltration rates are controlled by the clogging layer (which is the rule rawer than the exception for basins and ponds) , We water table must be at least 0.5 m (1.6 It)
|
From page 23... ...
Soil-Aquifer Treatment Where treated municipal wastewater or stormwater runoff are used in surface infiltration systems, the vadose zone and in some cases the aquifer act as natural, slow filters that typically reduce the concentration of various pollutants due to physical, chemical, and microbiological processes. Suspended solids are filtered out; biodegradable organic compounds are decomposed; microorganisms are adsorbed, strained out, or die because of competition with other soil microorganisms; nitrogen concentrations are reduced by denitrification; syn~etic organic compounds are adsorbed and/or biodegraded; and phosphorous, fluoride, and heavy metals are adsorbed, precipitated, or overwise immobilized.
|
From page 24... ...
Sometimes, dilution with native ground water is relied on to allow potable use of the recovered water without furler treatment. Proposed California regulations, for example, require that well water from SAT systems using treated municipal wastewater consist of not more Han 20 or 50 percent sewage (depending on the level of pretreatment and site conditions)
|
From page 25... ...
System Design and Pilot Projects Infiltration systems for artificial recharge of ground water or SAT systems for treatment and storage of waters of impaired quality must be tailored to local hydrogeology, quality of input water, and climate. In general, basin water depths should be less than 30 cm (1 ft)
|
From page 26... ...
Where there is no local experience with artificial recharge, adequate site investigations and local experimentation with a pilot or test project are necessary, especially if the source water is treated municipal wastewater or other lowquality water. The results from such pilot projects are then used to develop design and management criteria for optimal performance of the full-scale system.
|
From page 27... ...
Injection wells are much more vulnerable to clogging than surface infiltrationsystems because the infiltration rates into the aquifer around Me borehole are much higher than in infiltration basins. In addition, remediation of clogging in wells is much more difficult than in surface infiltration systems.
|
From page 28... ...
For this reason, dissolved air concentrations in the recharge water should always be as small as possible, and free-falling water in the recharge well should be avoided to prevent air entrainment. Where municipal wastewater is used for ground water recharge with injection wells, it must undergo extensive pretreatment, including advanced wastewater treatment (AWT)
|
From page 29... ...
Aquifer Storage and Recovery Wells A rapidly growing practice in artificial recharge is the use of aquifer storage recovery (ASR) wells, which combine recharge and pumping functions.
|
From page 30... ...
ENVIRONMENTAL E"ECTS The environmental effects of ground water recharge vary from site to site, and there can be both beneficial and harmful impacts. In general, however, the types of environmental effects that should be considered when planning recharge facilities range from ecological effects on soil, hydrologic, and aquatic ecosystems, to effects on species dependent on ripanan habitats, and to possible effects on people's use of the water resources for recreation.
|
From page 31... ...
In areas where the base flow of streams is supported by ground water discharge, additions to the storage and flow of ground water by recharge may result in higher sustained streamflows during low flow or drought conditions. The flow of springs might also be sustained at higher levels through dry periods by the higher ground water heads that would result from artificial recharge.
|
From page 32... ...
Stream pollution may increase and downstream appropriation rights may be jeopardized, as Novell, if recharge is not planned with an eye to the comprehensive needs of the region. The raised level of the water table caused by artificial recharge sometimes can have deleterious consequences.
|
From page 33... ...
As mentioned earlier, biochemical and geochemical reactions between the source water and the resident ground water and/or the aquifer materials could result in mobilization of chemical constituents that are part of the mineral framework of the aquifer. In addition, artificial recharge can leach anthropogenic cont~ninants from the vadose zone to ground water and move pollution plumes in aquifers to where they are not wanted.
|
From page 34... ...
1991. Proposed California regulations for ground water recharge with reclaimed municipal wastewater.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.