Water Treatment and Waste Management

07 Dec.,2022

 

containerized water treatment plants

Following a natural or man-made disaster, large amounts of contaminated water may need to be contained and treated before safe discharge to the environment or wastewater treatment plant. 

Drinking water could become contaminated from breaks in pipes that allow contaminants to intrude, intentional tampering, or loss of electrical power and pressure resulting in water stagnation and bacterial growth. Contamination needs to be flushed from the drinking water distribution system and the resultant contaminated water treated. 

Following a hurricane, flood, or tornado,  stormwater and wastewater systems can become contaminated and require treatment, or enhanced treatment, to protect the environment.  Response to a wide-area contamination incident will likely require that external building surfaces, roadway, and vehicles be decontaminated.  These decontamination operations can produce large amounts of water that must be treated before release to the environment or a wastewater treatment plant.  In addition to managing the contaminated water, approaches are needed to manage the contaminated treatment residuals (e.g., sludges, membranes).

Treatment 

Treatment of water related to the response to a homeland security incident can use some of the same technologies developed over the past 100 years for treatment in community water and wastewater system.  Treatment for homeland security incidents differs, however, in the types of contaminants that can lead to a need to treat the water on-site.  Such on-site treatment systems need to be compatible with potentially enormous volumes of contaminated water. 

A variety of robust, portable and on-demand treatment technologies exist that could potentially reduce high concentrations of toxic chemicals in water. Water on Wheels (WOW) mobile water treatment unit featuring activated carbon filtration and chlorination. However, measuring or accurately estimating how much contaminant concentration is reduced is not sufficient to demonstrate that water is safe for discharge.  Chemical oxidation, the most common form of treatment, can transform contaminants into different chemicals, known as transformation products.  These transformation products could be just as toxic or more toxic than the original chemical contaminant.  Thus, research is needed to evaluate treatment technologies for their ability both to reduce high levels of toxic chemicals and to produce treated water that is not toxic. Using a series of treatment technologies may further reduce toxicity of the most difficult to treat contaminants.

Evaluation of mobile, on-site emergency water treatment systems involves consideration of transportation issues, deployment, operation, cost and effectiveness for treating a wide variety of contaminants and concentrations.  Mobile systems can have multiple types of treatment technologies, be operated by multiple sources of power (grid, generator, solar), and operated by quickly trained first responders.

Ideally, the sequencing of on-site treatments will be rapidly deployable and configurable to treat many types of contaminants while minimizing the resulting waste stream. Since response activities will be site specific, and because there are a multitude of contaminants and water systems, EPA is researching decision support tools to help decision makers balance the many factors that go into the design and implementation of a treatment system at their site. Part of this process could be containing the contaminated water locally so that it can be treated without potentially releasing contaminated water to the environment.  Due to the potential volumes involved, this can be technically challenging, so EPA is researching innovative approaches that would use locally available equipment and assets.

Disposal of Residuals or Contaminated Water

Both treatment and decontamination frequently involve methods and reagents that generate both solid and liquid wastes.  Disposal of wastes can impact response activities, especially for types or amounts of contaminants resulting from homeland security incidents. For contaminated water in an urban environment, it is likely that at some point some of this contaminated water enters the area’s storm/waste water collection system. As this could impact the wastewater plant that receives this water, EPA is performing research to ensure that the unintended arrival of contaminated water at a treatment plant does not compromise the ability of a plant to provide its essential services to the community. 

Relatedly, due to the volume of contaminated water, even if such water is treated on-site, the treated water will need to be disposed of or discharged.  One potential route for doing this is to send it down the drain to the local storm/waste water system.  Naturally, the local utilities have expressed concern about this, so some of EPA’s research is aimed at providing adequate pretreatment of this water prior to drain disposal.  Pretreatment of various industrial wastes prior to discharge to wastewater systems is a routine approach in many industries, and EPA’s homeland security research focuses on contaminants and contamination scenarios for which there has been little work in devising pretreatment strategies.

In addition to contaminated water finding its way into stormwater drainage systems as a result of contamination response activities, stormwater systems, such as detention basins, retention ponds, wetlands, and pipe networks, can become directly contaminated from tanker truck wrecks, train derailments, and pipeline ruptures as well as rain runoff coming from buildings and roads contaminated from a wide-area attack or accident. EPA research is addressing numerous stormwater assets found in urban and suburban areas that can be retrofitted or designed to provide flow control, spillcontainment, and treatment of contaminated water.  These retrofit technologies can be used to improve water quality and aquatic habitats in urban areas on a daily basis as well as following an emergency. They do not require manned active operation or control of their operation and can be widely located across a watershed.

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