Adventus EHC-O

Adventus

In Situ Groundwater Bioremediation

EHC-O^® Controlled Oxygen Release Compound

Provision of Nitrogen Source

Natural biodegradation of hydrocarbons in the environment is often nitrogen limited. Hydrocarbon impacted sites have a lot of available carbon present but generally do not have sufficient available nitrogen present to support optimal bioremediation.  EHC-O provides a source of nitrogen in the form of ammonia to ensure adequate nitrogen is present for the indigenous microorganisms to utilize the available carbon (i.e., hydrocarbons).

Zeolite

Zeolite is a naturally occurring compound that has a very high cation exchange capacity (CEC), which serves two important functions in EHC-O.  Firstly, the CEC allows NH4 to be released slowly over time rather than all of it releasing immediately following injection.  When the NH4 dissolves into groundwater following injection, a portion of it interacts with the cation exchange sites of the zeolite, is transient held and slowly released as other cations move into the treatment zone with the groundwater and displaces the NH4.  This allows the NH4 to provide a prolonged source of nitrogen to the microorganisms.

Secondly, the CEC of zeolite traps calcium and thereby reduces or prevents the ‘self-encapsulation’ of calcium peroxide.  Self-encapsulation occurs in groundwater systems containing calcium or magnesium.  These cations interact with phosphates and form precipitates on the surface of the CaO2 and impede the release of oxygen.  This reaction is enhanced under the conditions of elevated pH that are present in the immediate vicinity of CaO2.  The cation exchange sites in zeolite bind the Ca and/or Mg and thereby prevents self-encapsulation.

Enhanced initial O2 release

The disruption of a groundwater system during injection often results in significant stimulation of the indigenous microbial population immediately following the disruption that slowly tapers off and stabilizes.   As a result, it is beneficial to have as much oxygen present as possible when treatment starts.  EHC-O has the highest initial release rate of all commercially available oxygen release compounds.  Following the first month, all oxygen release compounds provide aqueous oxygen at essentially the same rate and they all tend to have the same longevity: 12 months.