D.12 Water Disposal / Groundwater Recharge

Treated effluent and/or stormwater can be directly discharged into receiving water bodies (such as rivers, lakes, etc.) or into the ground to recharge aquifers, depending on their quality.General term for a liquid that leaves a technology, typically after blackwater or sludge has undergone solids separation or some other type of treatment. Effluent originates at either a collection and storage or a (semi-) centralised treatment technology. Depending on the type of treatment, the effluent may be completely sanitised or may require further treatment before it can be used or disposed of.Mixture of solids and liquids, containing mostly excreta and water, in combination with sand, grit, metals, trash and/or various chemical compounds. A distinction can be made between faecal sludge and wastewater sludge. Faecal sludge comes from on-site sanitation technologies, i.e. it has not been transported through a sewer. It can be raw or partially digested, a slurry or semisolid, and results from the collection and storage/treatment of excreta or blackwater, with or without greywater. Wastewater sludge (also referred to as sewage sludge) originates from sewer-based wastewater collection and (semi-)centralised treatment processes. The sludge composition will determine the type of treatment that is required and the end-use possibilities.General term for rainfall runoff collected from roofs, roads and other surfaces. Very often the term is used to refer to rainwater that enters a sewerage system. It is the portion of rainfall that does not infiltrate into the soil.Describes technologies for on-site collection, storage, and sometimes (pre-) treatment of the products generated at the user interface. The treatment provided by these technologies is often a function of storage and is usually passive (i.e. requires no energy input), except a few emerging technologies where additives are needed. Thus, products that are ‘treated’ by these technologies often require subsequent treatment before use and/or disposal. In the technology overview graphic, this functional group is subdivided into the two subgroups: “Collection/Storage” and “(Pre-)Treatment”. This allows a further classification for each of the listed technologies with regard to their function: collection and storage, (pre-) treatment only or both.Refers to the methods through which products are returned to the environment, either as useful resources or reduced-risk materials. Some products can also be cycled back into a system (e.g. by using treated greywater for flushing).A functional group is a grouping of technologies that have similar functions. The compendium proposes five different functional groups from which technologies can be chosen to build a sanitation system:
User interface (U), Collection and Storage/Treatment (S), Conveyance (C), (Semi-) Centralised Treatment (T), Use and/or Disposal (U).
A sanitation system is a multi-step process in which sanitation products such as human excreta and wastewater are managed from the point of generation to the point of use or ultimate disposal. It is a context-specific series of technologies and services for the management of these sanitation products, i.e. for their collection, containment, transport, treatment, transformation, use or disposal. A sanitation system comprises functional groups of technologies that can be selected according to context. By selecting technologies from each applicable functional group, considering the incoming and outgoing products, and the suitability of the technologies in a particular context, a logical, modular sanitation system can be designed. A sanitation system also includes the management and operation and maintenance (O & M) required to ensure that the system functions safely and sustainably. An underground layer of permeable rock or sediment (usually gravel or sand) that holds or transmits groundwater.
The utilisation of products derived from a sanitation system.
The liquid that has passed through a filter.
Water that is located beneath the earth’s surface.
A sanitation system in which excreta and wastewater are collected and stored or treated on the plot where they are generated.
The means of safely collecting and hygienically disposing of excreta and liquid
wastes for the protection of public health and the preservation of the quality of public water bodies and, more generally, of the environment.

Waste matter that is transported through the sewer.
An open channel or closed pipe used to convey sewage. See C.3 and C.4
The physical sewer infrastructure (sometimes used interchangeably with sewage).
Used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration.

The uses of the surface water body, whether for industry, recreation, spawning habitat, etc., and its size determine the quality and quantity of treated wastewater that can be introduced without deleterious effects. Alternatively, water can be discharged into aquifers. Groundwater Recharge is increasing in popularity as groundwater resources deplete and as saltwater intrusion becomes a greater threat to coastal communities. Although the soil is known to act as a filter for a variety of contaminants, Groundwater Recharge should not be viewed as a treatment method.

An underground layer of permeable rock or sediment (usually gravel or sand) that holds or transmits groundwater.
Water that is located beneath the earth’s surface.
A natural or man-made water body that appears on the surface, such as a stream, river, lake, pond, or reservoir.
Used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration.

Design Considerations

It is necessary to ensure that the assimilation capacity of the receiving water body is not exceeded, i.e. that the receiving body can accept the quantity of nutrients without being overloaded. Parameters such as turbidity, temperature, suspended solids, biochemical oxygen demand, nitrogen and phosphorus content (among others) should be carefully controlled and monitored before releasing any water into a natural water body. Local authorities should be consulted to determine the discharge limits for the relevant parameters as they can widely vary. For especially sensitive areas, a post-treatment technology (e.g. chlorination POST ) may be required to meet microbiological limits. The quality of water extracted from a recharged aquifer is a function of the quality of the wastewater introduced, the method of recharge, the characteristics of the aquifer, the residence time, the amount of blending with other waters, the direction of groundwater flow and the history of the system. Careful analysis of these factors should precede any recharge project.

An underground layer of permeable rock or sediment (usually gravel or sand) that holds or transmits groundwater.
The elimination of (pathogenic) microorganisms by inactivation (using chemical agents, radiation or heat) or by physical separation processes (e.g., membranes). See POST
A mechanical separation process using a porous medium (e.g., cloth, paper, sand bed, or mixed media bed) that captures particulate material and permits the liquid or gaseous fraction to pass through. The size of the pores of the medium determines what is captured and what passes through.Water that is located beneath the earth’s surface.
Any cellular or non-cellular microbiological entity capable of replication or of transferring genetic material (e.g. bacteria, viruses, protozoa, algae or fungi).
Any substance that is used for growth. Nitrogen (N), phosphorus (P) and potassium (K) are the main nutrients contained in agricultural fertilisers. N and P are also primarily responsible for the eutrophication of water bodies.
An organism or other agent that causes disease.A diverse group of unicellular eukaryotic organisms, including amoeba, ciliates, and flagellates. Some can be pathogenic and cause mild to severe illnesses.
An infectious agent consisting of a nucleic acid (DNA or RNA) and a protein coat. Viruses can only replicate in the cells of a living host. Some pathogenic viruses are known to be waterborne (e.g., the rotavirus that can cause diarrheal disease).
Used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration.

Materials

Groundwater Recharge does not require materials. Preceding technologies to add the water to the receiving water body, like Leach Fields D.9 or Soak Pits D.10 , require materials. Equipment for regular monitoring and evaluation of the groundwater quality might be needed.

Water that is located beneath the earth’s surface.

Applicability

The adequacy of discharge into a water body or aquifer will depend entirely on the local environmental conditions and legal regulations. Generally, discharge to a water body is only appropriate when there is a safe distance between the discharge point and the next closest point of use. Similarly, Groundwater Recharge is most appropriate for areas that are at risk of saltwater intrusion or aquifers that have a long retention time. Depending on the volume, the point of discharge and/or the quality of the water, a permit may be required. This technology should be implemented downstream of any settlement, as treated wastewater may still contain pathogens.

An underground layer of permeable rock or sediment (usually gravel or sand) that holds or transmits groundwater.
Water that is located beneath the earth’s surface.
An organism or other agent that causes disease.Used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration.

Operation and Maintenance

Regular monitoring and sampling is important to ensure compliance with regulations and to ensure public health requirements. Depending on the recharge method, some mechanical maintenance may be required.

Health and Safety

For Groundwater Recharge, cations (e.g. Mg2+, K+, NH4 +) and organic matter will generally be retained within a solid matrix, while other contaminants (such as nitrates) will remain in the water. There are numerous models for the remediation potential of contaminants and microorganisms, but predicting downstream or  extracted water quality for a large suite of parameters is rarely feasible. Therefore, potable and non-potable water sources should be clearly identified, the most important  parameters modelled and a risk assessment completed.

Any cellular or non-cellular microbiological entity capable of replication or of transferring genetic material (e.g. bacteria, viruses, protozoa, algae or fungi).
A diverse group of unicellular eukaryotic organisms, including amoeba, ciliates, and flagellates. Some can be pathogenic and cause mild to severe illnesses.
An infectious agent consisting of a nucleic acid (DNA or RNA) and a protein coat. Viruses can only replicate in the cells of a living host. Some pathogenic viruses are known to be waterborne (e.g., the rotavirus that can cause diarrheal disease).

Costs

There are no direct costs associated with this technology. There can be indirect costs depending on the recharge method, for example, construction of an outlet pipe or construction of a Soak Pit D.10 . Regular monitoring of groundwater requires the installation of monitoring wells.

Water that is located beneath the earth’s surface.

Social Considerations

The domestic or recreational use of water bodies at the location of recharge should be prohibited, as there are still some health risks particularly if this water is used for consumption. This would require an information campaign at this location, for example using warning signs.

Fact Sheet Overview

Input Products

Effluent
Stormwater

Output Products


Emergency Phase

Stabilisation +
Recovery + +

Challenging Ground Conditions

Semi-Suitable

Application Level / Scale

Household + +
Neighbourhood + +
City + +

Water-based and Dry Technologies

Water-Based

Management Level

Household + +
Shared + +
Public + +

Technical Complexity

Space Required

Objectives & Key Features

• Safe disposal
• Groundwater recharge

Strength & Weakness

  • Contributes to a “drought-resistant” water supply by replenishing groundwater
  • May increase productivity of water bodies by contributing to maintenance of constant levels
  • Discharge of nutrients and micro-pollutants may affect natural water bodies and/or drinking water
  • Introduction of pollutants may have long-term impacts
  • May negatively affect soil and groundwater properties

Selected References

Detailed information on Groundwater Recharge and Water Disposal

Tchobanoglous, G., Burton, F. L., Stensel, H.D. (2004): Wastewater Engineering: Treatment and Reuse. Metcalf & Eddy, New York, US

Seiler, K. P., Gat, J. R. (2007): Groundwater Recharge from Run-off, Infiltration and Percolation. Springer, Dordrecht, Netherlands

Guidelines for safe reuse of wastewater

ARGOSS (2001): Guidelines for assessing the risk to groundwater from on-site sanitation. NERC, British Geological Survey Commissioned Report, UK

WHO (2006): Guidelines for the Safe Use of Wastewater, Excreta and Greywater. Volume 3: Wastewater and Excreta Use in Aquaculture., Geneva, Switzerland

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