Managed Aquifer Recharge / Soil Aquifer Treatment

Concept

Managed Aquifer Recharge (MAR) is a natural water / wastewater treatment process, in which water is introduced into the groundwater via soil infiltration through spreading basins, vadose zone injection wells or direct injection methods (Sharma et al., 2012). Soil Aquifer Treatment (SAT) is a widely used MAR method, in which treated effluent is infiltrated through spreading recharge basins (Fox et al. 2005) (Figure 1). SAT aims to improve water quality regarding suspended solids, biodegradable materials, bacteria, viruses, and other microorganisms, while achieving significant reductions in nitrogen, phosphorus, and heavy metals concentrations (US EPA, 2012).

Figure 1: Typical SAT infiltration pond with and SAT system components Sources: Bouwer, 2002; Sharma & Kennedy, 2017.
Figure 2: Different types of SAT facilities for wastewater treatment: a) dug well in Shafdan (AquaNES Demo Site 7); b) reed bed on sand dune in Agon-Coutainville (AquaNES Demo Site 8)
Types

Land availability determines the type of SAT to be adopted. Spreading basins (Figure 3a: Types A and B) require availability of sufficient land and are applied in case of unconfined aquifers with unsaturated zones. These SAT types require high permeable soils within a reasonable depth of the non contaminated zone. The aquifer below the vadose zone should be sufficiently transmissive and not confined to form groundwater mounds beneath the basin for efficient recharge (Chol Deng Thon Abel, 2014).

When land availability or top soil suitability do not permit the use of surface spreading, effluent is applied via trenches or wells constructed directly into the unsaturated part of the aquifer (Figure 3a: Types C and D).

Figure 3: a) Different types of SAT systems (Source: Bouwer, 1999) b) Soil forest SAT system for drinking water production in Lange Erlen, Basel (Switzerland) (AquaNES Demo Site 6)
Function

The operation of SAT systems involves wet and dry cycles to avoid clogging and optimize redox soil conditions (Amy & Drewes, 2007).

At the basin-soil interface, the combined effects of sedimentation, filtration, aeration, and microbial growth lead to the formation of a biologically active zone that may become impermeable. Wet and dry cycles which last several days prevent clogging; the basin-soil interface does not become impermeable (Fox, Abonshanp, & Alsamadi, 2005; Bouwer, 2002).

During dry cycles re-aeration takes place, increasing the redox potential and providing oxidative conditions for organic matter and NH4 removal. Ideally, SAT systems should comprise numerous basins so that some basins can be flooded while others are drying.

During groundwater recharge through the vadose zone and transport through the groundwater aquifer, water quality improvements occur. Sorption and biodegradation processes in the soil are mechanisms that can reduce or remove microbial and other contaminants from wastewater.

Figure 4: Recharge Basin during Wet (left) and Dry (right) Cycles in Dan Region (Tel-Aviv, Israël) (Source: Idelovitch, Icekson-Tal, & Michail, 2003)

Table 1: Pollutant Removal in SAT Systems*

(Source: Sharma and Kennedy, 2017)

Pollutant

Source water

PE

SE

TE

Heavy metals

50-100%

50-100%

20-100%

TSS/Turbidity

86-100%

Pathogens

•Bacteria including indicators

•Viruses

•Giardia and Cryptosporidium

•1.2-6.9 log

•4.0 log

•1à2 log

•3.0-6.5 log

•0à4.0 log

•1à2 log

•2.4-3.0 log

•0.4-4.0 log

•1à2 log

Nitrate

57-100%

3-90%

0-22%

Ammonium

17-100%

0-99%

17-85%

Phosphate

4-100%

30-99%

37-80%

Organic micropollutants**

25-100%

20-100%

10-100%

Bulk Organic matter (DOC/TOC)

10-91%

10-90%

20-80%

Salinity

Not removed

Hardness

Not removed

PE=primary effluent, SE= secondary effluent, TE= tertiary effluent * SAT performance is site specific. ** Highly dependent on type of organic micropollutant, source water quality matrix and redox conditions

References & Sources for Further Reading
  • Amy, G., & Drewes, J. (2007). Soil aquifer treatment (SAT) as a natural and sustainable wastewater reclamation/reuse technology: fate of wastewater effluent organic matter (EfOM) and trace organic compounds. Environ. Monit. Assess., 129(1-3), 19-26. doi: 10.1007/s10661-006-9421-4.
  • Bouwer, H. (2002). Artificial recharge of groundwater: hydrogeology and engineering. Hydrogeology Journal, 10(1), 121-142. doi: 10.1007/s10040-001-0182-4.
  • Bouwer, H. (1999). Artificial recharge of groundwater: Systems, design and management. In L. W. Mays (Ed.), Hydraulic Design Handbook (pp. 24.1-24.44) . New York, NY: McGraw-Hill.
  • Chol Deng Thon Abel (2014). Soil Aquifer Treatment: Assessment and Applicability of Primary Effluent Reuse. Netherlands: UNESCO-IHE PhD Thesis Series.
  • Fox, P., Aboshanp, W., & Alsamadi, B. (2005). Analysis of soils to demonstrate sustained organic carbon removal during soil aquifer treatment. J. Environ. Qual., 34(1), 156-163.
  • Idelovitch, E., Icekson-Tal, N., Avraham, O., & Michail, M. (2003). The Long-Term Performance of Soil Aquifer Treatment (SAT) for Effluent Reuse (Vol. 3).
  • Sharma, S. K., & Kennedy, M. D. (2017). Soil aquifer treatment for wastewater treatment and reuse. International Biodeterioration & Biodegradation, 119, 671-677. doi: https://doi.org/10.1016/j.ibiod.2016.09.013.
  • Sharma, S. K., Ernst, M., Hein, A., Jekel, M., Jefferson, B., & Amy, G. (2012). Treatment Trains Utilising Natural and Hybrid Processes. In C. Kazner, T. Wintgens, & P. Dillon (Eds.),  Water Reclamation Technologies for Safe Managed Aquifer Recharge (pp. 239-257). UK: IWA Publishing.
  • US EPA, United States Environnemental Protection Agency. (2012). Guidelines for Water Reuse (EPA/600/R-12-618). Washington, DC: US EPA.

If you want to learn more about SAT in cNES click here ...

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