Contaminated Water Filtration – Passive Barrier System

A PBS is a convenient, easy and simple solution for contaminated water filtration, effectively treating surface and ground water to remove pollutants from the environment. The PBS design can be flexible by incorporating various sizes of porous bags, soxx, cell systems and geosynthetics.

The “Water Restore” PBS is low cost and can be mobilised to site and set up relatively quickly. Once installed water flowing in and out of the PBS can monitored to establish performance to schedule routine maintenance.

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Common Contaminates Found In Water

Metals removed include Arsenic (As), Aluminum (Al), Cadmium (Cd), Cesium (Cs), Chromium (Cr), Cobalt (Co), Copper (Cu), Iron (Fe), Lead (Pb), Manganese (Mn), Magnesium (Mg), Mercury (Hg), Molybdenum (Mo), Nickel (Ni), Silver (Ag), Strontium (Sr), Uranium (U) and Zinc (Zn).

Nutrients removed include Ammonia (NH3), Nitrate (NO3), Nitrate (NO3-) and Phosphate (PO43).

Per-and Polyfluorinated Substances (PFAS) removed include PFAS, PFOA and PFHxS.

Contaminated Water Filtration – Common Media’s Utilised To Restore Water

Media Type – Carbon

Activated carbon is the most commonly used approach Worldwide to treat water in “pump and treat” systems. It is also used to treat contaminant vapours removed from contaminated soil and groundwater by soil vapor extraction and other clean up methods.  Activated carbon is the most versatile adsorbent because of its large surface area, polymodal (but essentially microporous) porous structure, high adsorption capacity, and variable surface chemical composition.

Granular Activated Carbon (GAC) is used to filter harmful chemicals from contaminated water and air.  GAC is composed of granules derived from coal, wood, nutshells or other carbon-rich materials.  As contaminated water flows through activated carbon, the contaminants sorb (stick) to the surface of the granules and are removed.  GAC reduces odour and removes a wide range of contaminants dissolved in groundwater or surface water.  Pollutants removed include a variety of industrial chemicals including but not limited to hydrocarbons, polychlorinated biphenyls, pesticides, chlorinated solvents, phenols, dioxins, radon and a variety of heavy metals.

As the contaminated water or air flows through the GAC, the contaminants sorb to the outer and inner surfaces of the granules.  The water exiting the container will be cleaner. Regular testing of exiting water can conducted to check contaminant levels.  If testing shows that some contaminants remain, the Passive Barrier System volume can be increased so the water is treated to meet desired levels.  The GAC will need to be replaced when the available surfaces on the granules are taken up by contaminants and additional contaminants can no longer sorb to them.  The “spent” GAC may be replaced with fresh GAC or “regenerated” to remove the sorbed contaminants.  The spent GAC is sampled, laboratory analysed, classified and disposed at a suitably licenced facility or regenerated for reuse.  To regenerate spent GAC, it is heated to very high temperatures to destroy the contaminants to enable reuse.

Media Type – Zeolite

Zeolite is naturally occurring volcanic rock.  In water treatment, the most common is the clinoptilolite Zeolite family of aluminosilicates, made of varying concentrations of aluminum silica, oxygen and other elements like calcium (Ca), potassium (K) and sodium (Na).  Their structure and composition make them microporous and highly inclined for cation exchange capabilities. Due to its high pore density, zeolite has a highly effective surface area, meaning it can capture high concentrations of physical contaminants.  Zeolite utilises the process of adsorption to capture and remove undesirable pollutants.  Zeolite water treatment is effective as particles adhere to the surface of the media as well as passively getting caught between grains.

A unique advantage of zeolite is its combination of physical, chemical, adsorption, ionisation, reduction and catalytic properties.  Zeolite can adsorb ammonia, nitrate, nitrogen, hydrogen-sulfide, heavy metals, carbon-oxygen, oil-derivates, etc.  It also can adsorb and/or separate the following with catalytic effect: potassium (K), iron (Fe), manganese (Mn), strontium (Sr), lead (Pb), copper (Cu), silver (Ag), mercury (Hg).  The main advantage of zeolite is its physical/chemical adsorption, ion exchanging and catalytic properties, uniform pore structure, large pore volume which reduces heavy metals, ammonium and hydrogen compounds and other chemicals through its unique adsorption capabilities.

Zeolite, in particular the clinoptilolite type, has many pores, therefore it does not just capture particles between grains but also adsorbs pollutants onto the surface of the media effectively capturing them.  This is done in part by the mineral’s capacity for cation exchange, whereby it takes on positive ions from the water (i.e. dissolved metals, sodium, ammonia) and replaces them with something else that was already attached to the media’s ion exchange sites.

Media Type – Lime

Many industrial processes generate acidic wastewater, which must be treated before release.  Lime serves to neutralise acids while also precipitating various metals into solids that can be recovered.  Other, more caustic agents, such as caustic soda, could perform similar functions, but lime is cheaper and safer to handle.  Lime has numerous applications in water treatment and is widely used as a softener for the precipitation of magnesium compounds and for the removal of carbonate hardness.  For the removal of turbidity, lime is used extensively to produce the proper pH zone for maximum coagulation results.  It is also added as a secondary treatment to adjust the pH value and reduce corrosion.  Lime has a high bactericidal action, reduces organic matter and thus assists in the removal of odours from water.  High calcium content lime and/or magnesium oxide is used for water treatment.

Lime is used in conjunction with alum or iron salts for coagulating suspended solids in order to remove turbidity from water. It serves to maintain the proper pH for most satisfactory coagulation conditions. In some water-treatment plants, alum sludge is treated with lime to facilitate sludge thickening on pressure filters.  Lime controls the environment required for the growth of bacteria and certain viruses. This application of lime is utilized where “phenolic water” exists, because chlorine treatment tends to produce unpalatable water due to the presence of phenol. This process, called ‘excess alkalinity treatment’, also removes most heavy metals.  One of the most common methods of removing silica from water involves the use of dolomitic lime. The magnesium component of this lime is the active constituent in silica removal.  Lime is also used to remove manganese, fluoride, organic tannins and iron from water supplies.

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Common Applications For Passive Barrier Systems

  • Discharged water from dewatering tubes
  • Discharged water from dredging
  • Contaminated water stored in industrial tanks from production and manufacturing plants
  • Storm water from construction and industrial sites
  • Surface and subsurface water passing through / over contaminated soils
  • Prior contaminated locations such as Airports, Defence Bases, Industrial zones

Common Installation Points For Passive Barrier System

  • Drainage channels and culverts capturing contaminated runoff
  • Drainage inlet and outlet points capturing contaminated runoff
  • Stormwater inlets
  • Creeks and streams capturing contaminated runoff
  • Perimeter control around contaminated sites
  • Perimeter control around dewatering tubes

 

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At Project Material, we are able to tailor the best method, material, media, installation and testing to suit every project. Our expertise in specialised materials allows for an array of product combinations and layouts to meet EPA compliance and restore contaminated water back to the environment in its natural form.

 

Related Project – PFAS Remediation – Williamtown RAAf Base

PFAS Remediation Passive Barrier System