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Embed code for: A_Canadian_Company_Discovers_a_Method_for_Removing_Mercury_from_Wastewater_Streams
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A Canadian Company Discovers a Method for Removing Mercury from Wastewater Streams
Author Mr. Don Wilson
Zorbtech Environmental Solutions (Zorbtech) is a small R&D application research company located in the Province of Ontario. Zorbtech has developed one of the most important environmental technologies in the world. This technology is aimed at reducing or eliminating one of the most dangerous pollutants contaminating our environment. This contaminate is mercury. The release of mercury into the environment can create widespread environmental damage, and, more importantly, effect the health of humans.
Zorbtech has invented and developed a adsorbent-based technology which can remove 99.999% mercury from wastewater streams. The technology has been tested and was installed at a wastewater treatment plant located in the State of Ohio in 2012.
The site chosen for the demonstration was the wastewater treatment plant operated by the City of Elyria in the State of Ohio. The plant manager agreed to allow the pilot plant to be installed with the intent to evaluate the capability of the technology in terms of removing soluble mercury down the required limits as set out in their permit from the Ohio EPA.
Although numerous bench tests exist which illustrated how a particular technology can remove mercury removed from various aqueous streams, this is the first implementation of a real pilot plant demonstration in North America, which illustrates the use of how one particular technology can be used for the removal of mercury from an actual wastewater treatment plant.
OHIO EPA Supported Research
The OHIO EPA supported Zorbtech in the implementation of this pilot plant. The Ohio EPA indicated that Zorbtech is the only company in North America which has published real time data illustrating the use of an adsorbent exclusively for the reduction of mercury in an actual operating wastewater treatment facility.
Major Benefits from the Pilot Plant Study
The benefits and more importantly the information generated from the modifications to the hardware during this trial allowed the research team to arrive at a set of conclusions which could lead to the design and engineering of a full scale wastewater treatment process. Not only did the technology process prove to be highly effective in terms of reducing the level down to the 1.3ppt as set out in the GIL regulation, but, also in terms as to how cost effective the process could be in a full scale operation. This pilot study represents for the first time that the economics of implementing a new wastewater treatment technology could be cost –effective.
Scientific Description of Technology
The Zorbtech Environmental Solutions wastewater treatment process technology is based on the two new innovative technologies; (a) development of new dithiocarbamate which adsorbs mercury on to it surface, (b) a process whereby the aqueous stream is reacted with dithiocarbamate to adsorb the soluble mercury on to its surface.
The method employed to treat wastewater streams using the Zorbtech adsorbent comprise of three steps.
Removing, where appropriate all suspended solids from the wastewater stream.
Reacting the outflow from the above the treatment with the adsorbent in a reaction vessel
Removing spent adsorbent from the above vessel and solidifying the adsorbent thereby encapsulating the mercury laden compound.
Pilot Plant Setup and Operational Description
The following images represents the actual pilot plant and the vessels used in the process. It was determined that in order for the adsorbent to be highly efficient, a pre-treatment filtration system would be needed in order to remove the suspended solids The pre- treatment system consisted of sand media contained in .5 micron media filter.
The above Reaction Vessel contains the absorbent which strips the soluble mercury from the wastewater.
The following image represent the chemical reaction which occurs in the reaction tank.
General Equipment Design
The technology can be scaled up to treat any volume of water. In the Elyria Wastewater Plant, the average daily volume was 3MGD (3,000,000 gallons per day). In a full scale operation at this plant, a 250,000 gallon sand filter system would remove 99% of all suspended solids.
Here is the image of a full scale fluidized bed reaction vessel
The above image represents the Zorbtech Treatment Process using a full scale reaction tank, known as the Zorbtech Mercury Removal System.
Results of Pilot Plant Demonstration
In the above table , the first column shows the level of mercury which was contained in the raw water coming from the clarifier. The second table illustrates how the Zorbtech process reduces mercury. The volume of water pumped through the system was 69,000 gallons. The Mercury level never exceeded 1.3 ng/L.
The Zorbtech Treatment Advantages: Complete Flexibility
The system provides flexibility. Facilities that have only secondary treatment may need to add tertiary treatment to remove as much solids as reasonably possible. The pilot system provides the ability to determine if tertiary treatment is needed.
Additional studies are needed to find a true cost per gallon of treatment using the DioZorb adsorbent. At the current estimated cost, exclusive of capital costs, the DioZorb significantly reduces the perceived cost for the reduction of mercury in wastewater. A secondary system such as Elyria’s would benefit greatly having a tertiary treatment system and a final polishing system. As seen by the data, even when the facility had high mercury levels in the secondary system, the tertiary unit and final polishing unit still maintained a consistently low level mercury discharge under the 1.3ng/L limit. an actual operating wastewater treatment facility.
The following image represent the chemical