Liberty Hydro Explanation of Technology: 

For application to flue gas desulfurization wastewater at coal burning 

power plants

Introduction

Liberty Hydro, Inc. has developed a reactive media designed to reduce selenium (in all forms) from FGD 

wastewaters, using zero valent iron (ZVI) on a reticulated foam substrate. The ZVI system will reduce 

heavy metals and entrap the contaminants within the media matrix, producing a wastewater able to 

meet the proposed effluent guidelines. 

The technology, termed ZVI BlueTM, was installed at several coal burning power plants during 2013 and 

2014. When used effectively, ZVI BlueTM is the anchor technology in a three step treatment train 

consisting of 1) Physical/Chemical treatment followed by 2) a simple bio system (to remove nitrates), 

followed by 3) ZVI BlueTM reactive media to remove selenium and other metal contaminants. The testing 

was designed to determine effectiveness of the three stage treatment process and to determine cost 

effectiveness of the concept. The results showed that the proposed three stage treatment system can 

be optimized to meet the proposed effluent limits and can be done so, cost effectively. 

Liberty Hydro was established in 2009 and has focused its efforts to develop advanced technologies to 

reduce selenium, mercury and arsenic from wastewaters in coal mines and coal burning power plants. In 

2013, Liberty Hydro evaluated waters from numerous power plants in North America. That analysis 

showed that the best treatment option is a three step treatment train as described above, which we 

believe is the foundation for Best Available Technology. 

FGD Wastewater Treatment Evaluation

Evaluation of wastewaters from several power plants showed the material to be:

 Variable in pH, ORP and degree of TDS and TSS;

 Selenium levels were also variable due to factors such as type of coal, effectiveness of 

flue gas desulfurization, and seasonal factors;

 Nitrate levels were also highly variable;

 Most power plants do not seem to use primary treatment to prepare their water prior 

to release.
These, and other factors, add to the complex nature of the treatment required. A single solution, or 

“magic bullet”, will not be sufficient or cost effective under all conditions to manage selenium from 

these wastewaters. As a result of this initial evaluation, the use of a three step treatment train was 

evaluated to treat FGD wastewaters.

Primary Treatment (physical/chemical)

Primary treatment of raw waters is a well-known in the water and wastewater treatment industry. 

Primary treatment uses pH adjustment (lime addition) followed by the addition of coagulants (iron salts) 

and polymers (cationic, anionic or nonionic) followed by clarification and settling. Primary treatment 

allows for the removal of some metals, adjustment of pH and ORP (important in selenium removal) and 

the removal of TSS and TDS. Water thus treated is more uniform and thus is better for treatment by the 

next stage treatments. 

Biological Treatment (nitrate removal)

Biological treatment of FGD waters has been considered as a leading technology by the Environmental 

Protection Agency. Unfortunately, the variability of FGD contamination levels and lack of primary 

treatment all contribute to the difficulty of using one technology to meet the proposed effluent limits. 

Liberty Hydro Inc. evaluated biological technology as a methodology to manage nitrates. Nitrates are 

known to interfere, at some level, with selenium reduction from zero valent iron, so Liberty Hydro used 

a simplified Up-Flow Anaerobic Packed bed Reactor (UAPBR) as a method to reduce nitrates in 

preparation for the anchor technology, ZVI BlueTM, to remove selenium. Nitrates are also part of the 

proposed effluent guidelines so the use of a biological technology, to manage nitrate, makes sense as 

part of an effective three step treatment train. 

The biological system uses a specific blend of non GMO, class 1, naturally occurring consortia of 

microbes designed to specifically focus on nitrate removal. The consortium consists of various forms of 

denitrifying species of microbes. The microbes are initially inoculated into a media consisting of natural 

coconut char as a carbon source. The carbon source and the nitrate contamination serve as the food 

source for the microbial action. Influent water coming from the primary physical chemical treatment 

system is ideal for processing by such a microbial system.

ZVI Blue

ZVI BlueTM uses the power of zero valent iron (ZVI) to reduce all forms of selenium to an insoluble 

material which remains bound to the reticulated active foam matrix. ZVI creates a shower of electrons 

which will aggressively reduce selenate, selenite and other forms of selenium to a metallic form. ZVI is 

very effective in reducing selenium through the following mechanism. 
Summary of pilot plant treatment data

Two pilot plants were operated at two different coal burning power plants. One facility was treated 

using a three step treatment train while the other facility was treated using physical/ chemical 

treatment followed by ZVI BlueTM. Note this second facility did not have nitrate contamination so the use 

of a biological nitrate removal system was not required. 

Once the treatment systems were optimized, results showed that BOTH facilities were able to meet the 

proposed effluent guidelines on a consistent basis. Continued testing is designed to show the life cycle 

of the reactive media and management of effluent over a longer period of time. 

Cost Estimate

Each power plant will require a treatment train specifically designed to manage its specific water 

chemistry. Liberty Hydro did provide a detailed cost estimate for a three step treatment train for a 350 

gpm wastewater system. 

The total capital cost for such a system is $45 million which includes a primary physical/chemical 

treatment step, a simple biological nitrate management step and anchor ZVI technology for metals 

removal. Operating costs for the full system is estimated to be $3.5 million annually. This results in a 20 

year lifetime cost of $115,000,000 (2014 dollars). This results in a cost of approximately $31 per 

thousand gallons treated over the 20 year period. 
Conclusion

Treatment of FGD waste waters requires a multi-step approach to meet proposed effluent guidelines

 Primary physical/chemical treatment

 Biological treatment to manage nitrate

 ZVI Blue anchor technology to remove Selenium, Arsenic and other heavy metals

Cost of treatment for a 350 gpm system is estimated to be approximately $30 per thousand gallons

treated.

Additional testing is required to develop specific treatment options for specific FGD effluent waters. We 

can provide EPA with additional testing data when available. 

The data shows that the three step system outlined above can effectively and economically allow coal 

burning power plants to meet the proposed ELG’s for selenium. 

We look forward to working with you to help the industry and the agency meet their goals. 

Sincerely

Phil Farina

Executive Sales

419-346-8848

Phil.farina@libertyhydro.com