Introducing an Advanced

Technology for Sustainable

Nitrate Removal for

Ground Water Treatment

Introducing an Advanced

Technology for Sustainable

Nitrate Removal for

Ground Water Treatment

Sherwin Gormly, PhD, and Charles Borg

Applied Process Technology

Nitrate contamination is a pervasive problem for water systems due to natural and agricultural activities

http://www.cipcorp.com/i

ndustrial.htm

http://cropwatch.unl.edu/archives/200

1/crop01-25.htm

http://www.dnrec.state.de.us/dnrec2

000/Divisions/Soil/dcmp/cdag.htm

http://www.state.sd.us/denr/DES/S

urfacewater/Virtual/virtual.htm

http://www.southedgeseeds.com.au/project1.htm

– natural decomposition of plant and animal matter

– inefficient application of fertilizer

– waste discharged from

• food processing plants

•confined animal facility operations

•municipal and private wastewater treatment systems

Solutions to the nitrate problem:

Limit further contamination of waters by controlling the release of nitrate and nitrate precursors at their source

Secure alternative clean water supplies by drilling new wells, deeper wells, switching to surface water supplies, or importing drinking water

Treat contaminated waters (all or a fraction of the flow and/or blend)

(USDI, Bureau of Reclamation)http://la.water.usgs.gov/nawqa/liaison/gwgeneral.htm

Treating contaminated waters

Physical-chemical treatment:

Ion exchange and reverse osmosis are the most common

methods and have several substantial advantages

• Proven technologies for nitrate removal

• The equipment is readily available

http://groundwaterprogram.army.mil/community/facts/ion_jun04.html http://www.pseg.com/media_center/photogallery/gallery4.jsp

Treating contaminated waters

Physical-chemical treatment:

Ion exchange and reverse osmosis however also share

several substantial drawbacks

• Treatment produces substantial amounts of solid waste treatment residuals that may be classifiable as

hazardous waste depending on the ground water

• The process requires expensive and energy

intensive maintenance and logistical support

http://www.galleries.com/minerals/elements/arsenic/arsenic.htm

Arsenic is a common treatment

residual in groundwater

treatment world wide

Treating contaminated waters

Biological treatment:

Biological treatment works on the principle of microbial

reduction of nitrate (NO3-) to nitrogen gas (N2) by bringing

together the:

1. Contaminants (e.g., nitrate)2. Bacteria able to reduce them

3. An electron-donor substrate that the bacteria can oxidize to complete an oxidation reduction couple

Treating contaminated waters

Biological treatment:

The biological denitrification process has several

advantages relative to physical-chemical treatment:

• The nitrate is destroyed, not just transferred to a

secondary waste stream that requires subsequent

treatment and disposal; the end product is nitrogen gas

• There are no treatment residuals (waste brines) to manage

• It has been well-studied, is generally accepted in concept, and is widely used in practice for

wastewater treatment where it has been found to be

less expensive than physical-chemical treatment methods

Typically denitrification in water treatment isHeterotrophic denitrification.

This is the most common strategy for drinking water primarily because of its familiarity due to wide scale

and successful use in wastewater treatment.

Heterotrophs use an organic carbon as the electron donor

In wastewater treatment, the waste provides these carbon feeds

In drinking water treatment, the carbon substrate

must be added

6NO3- + 2CH3OH →5CO2 + 3N2 + 7H2O + 6OH

-

The problems in using the conventional nitrate metabolic model to achieve optimal drinking water treatment are:

1. Large amount of expensive carbon substrate feed compounds must be provided to the process at the

process site (a logistical drawback similar to that encountered with physical chemical processes)

2. Post-treatment is typically necessary to remove electron

donor residuals in the treated water that occurs due to

overdosing or fluctuations in the influent nitrate concentration

These two points indicate that conventional heterotrophic

nitrate removal is not an ideal and sustainable biological

solution

Autotrophic denitrification represents a potentially superior alternative

It is not as well studied as heterotrophic denitrification,

however a significant body of information is gathering for use of hydrogen as the electron donor.

Hydrogen gas (H2) has several advantages:

• It is currently the least expensive donor per equivalent

of electrons supplied• It is compatible with a post hydrocarbon fuel energy

infrastructure and/or on site alterative energy generation

options• Non-toxic to humans

• Supports the growth of autotrophic bacteria, which do not need an organic carbon source

• Produce lower biomass yields than heterotrophic

denitrification for the same level of treatment

Autotrophic denitrification using

hydrogen gas

NO3- + 5H2 + 2H

+→2N2 + 6H2O

Or

2.5H2 + NO3- → 0.5N2 (gas↑) + 2H2O + OH-

Technical concepts for advanced and

sustainable biological nitrate removal

APT MBfR

High efficiency, low carbon footprint, nitrate removal from

groundwater

�Treatment to drinking water

standards

Achieved through Autotrophic denitrification

Highly scaleable technology

Biofilm

Porous

polyethylene

Dense

polyurethane

H2 gas

Bundle of

hollow fiber

H2 gas

manifold

Biofilm

Porous

polyethylene

Dense

polyurethane

H2 gas

Biofilm

Porous

polyethylene

Dense

polyurethane

H2 gas

Bundle of

hollow fiber

H2 gas

manifold

Bundle of

hollow fiber

H2 gas

manifold

Bundle of

hollow fiber

H2 gas

manifold

NO3-

N2 gasFlow

~ 280 µm

~ 1 µm thick;

(non-porous;

Hydrophobic)

Advanced Nitrate Reduction

Hollow-Fiber Membrane Bio-Reactor

Conclusions

Nitrate contamination of groundwater is a large and growing problem

Current treatment process paradigms and related

hardware solutions are resource intensive

Autotrophic denitrification is potentially a high efficiency

low carbon footprint nitrate contaminated removal

technology for groundwater treatment to drinking water

standards

The requirement for hydrogen and electric

power only gives this technology the potential

for isolated operability/distributive treatment,

low carbon footprint operations, and seamless

integration into a hydrogen based energy

infrastructure

Questions