LGAC vessels are used to treat wastewater by removing dissolved organic compounds which have contaminated water sources. In general GAC vessels are used for treatment of ground water, storm water, municipal water and wastewater treatment. The contaminated water is pumped through the vessel, which contains granular activated carbon that adsorbs the contaminants. This adsorption process removes the dissolved organic compounds from the process flow.
The activated carbon media within a LGAC vessel has a finite lifespan before it begins to breakthrough and allows contaminants to pass through the filter. Carbon vessels are typically installed in series in a lead/lag, series orientation to ensure no contaminants reach the downstream process. Once carbon is spent in the lead vessel, it is replaced with fresh carbon and the orientation of the vessels is switched usually via a valving/piping header. After the change-out, the former lag vessel becomes the new lead vessel and vice versa. This configuration helps utilize the carbon adsorption capacity as efficiently as possible.
Typical Treatment Application
- Storm water filtration
- Industrial water filtration
- Municipal water filtration
- Remedial water filtration
- Waste water filtration
- Pool water filtration
- Drinking water for dissolved organics
- Groundwater remediation
- Removal of dissolved chlorinated organic compounds
- Storm water run off
- Removal of dissolved pesticides
- Removal of semi-volatile organic compounds
- Taste and odor removal
- Reverse osmosis
- Potable water filtration
- Irrigation water filtration
- Water park features water
- Removal of GRO (gas range organics)
- Removal of DRO (diesel range organics)
Compounds Commonly Adsorbed in GAC Vessels
- Methyl-ethyl-ketone (MEK)
- Polynuclear-aromatic-hydrocarbons (PNAs)
- Polychloro-biphenyls (PCB's)
- Methyl-isobutyl-ketone (MIBK)
GAC or Air Stripping
- Trichloroethene (TCE)
- Tricholoroetheane (TCA)
- Dichloroethane (DCA)
- Carbon tetrachloride
- Methyl-tert-butyl ether
- Freon 12
- Dibromochloropropane (DBCP)
|The picture above shows contaminants being “absorbed” by the carbon. Carbon lifespan is spent more quickly by larger compounds. This has a direct impact on the bed life of the carbon.
Depending on concentration, flow and other water quality characteristics, pre-treatment options may be required in addition to GAC treatment.
Multimedia Filtration - if high inorganic solids loading is present
Oil water separators - if free phase product is present
H2K offers multiple treatment options that can accommodate a large variety of applications. H2K is able to provide performance modeling to determine sizing and bed life based on provided analytical data. Water flow, contaminants and concentrations, discharge pressure, and discharge criteria are all basic factors in determining the proper carbon filter size.
Contaminants & concentrations: LGAC vessels provide satisfactory adsorption performance so long as the activated carbon has sufficient time / capacity to adsorb contaminants. Treatment process time through the carbon bed is commonly referred to as Empty Bed Contact Time (EBCT). Basically to time it takes the water to flow through the carbon vessel. The larger diameter the vessel the longer EBCT for a given flow rate. In general larger contaminants will use up carbon more quickly and cause more frequent change-outs. Carbon modeling looks at all the parameters to determine a recommended vessel size, carbon quantity and predicted carbon bad life.
Process flow rate: As flow rate through a carbon vessel increases, carbon will be used more quickly and pressure drop across the filter will increase. The proper balance between vessel size and flow rate must be considered to avoid over or under sizing the vessels.
Discharge criteria: Depending on the destination of treated water, different types and grades of activated carbon are available for use. A high quality regenerated activated carbon is commonly used in applications with non-potable discharge locations while virgin activated carbon is required for use in potable water applications.
Design Options Available
LC Series – H2K’s standard LGAC line is rated for flows up to 400 GPM, with up to 10,000 Lbs. of carbon. Pressure ratings range from 45 – 75 psi
LCA Series - ASME – ASME stamped vessels, rated for flows up to 900 GPM, with up to 30,000 lb. carbon capacity are available with design ratings up to 150 psi.
LCF Series - FRP – Fiberglass LGAC vessels are lightweight and very portable. These vessels can handle up to 120 GPM and hold up to 1,250 Lbs. of carbon.
Lead/lag and backwash piping headers – Vessels can be set-up with a PVC or steel valve header which allows easy switch of lead and lag vessels. Backwash headers are also available which allows reverse flow through the vessels to remove surface fouling from the carbon bed.
Transfer pumps and instrumentation – H2K Technologies offers a full line of centrifugal and positive displacement pumps to feed water through LGAC vessels. Safety switches and local indicating transmitters are available if automation and telemetry are a desired part of your system.
This project treated many dewatering ponds on the client’s property. They were treating benzene and gasoline range organics. H2K fabricated a portable, easy to use fiberglass GAC assembly to effectively treat up to 100 GPM for sewer discharge.
Pipeline Rupture Response
H2K Technologies supplied a full-scale water treatment system including a pair of ASME-stamped liquid phase carbon vessels. These vessels treated 200 GPM for BTEX and polished the water for discharge to sewer. These vessels feature a lead/lag piping header, carbon slurry lines for ease of carbon change-out, and backwash piping to mitigate fouling.
Rental Water Treatment Sheds
As part of a large scale dual phase remediation project, liquid phase carbon vessels were used to treat hydrocarbons from recovered groundwater. These carbon vessels were designed to polish 140 GPM water flow after treatment in an air stripper unit. This project featured access ladders and roof hatches to allow access for carbon change-out with a vacuum truck and re-loading of fresh carbon fill.