EBR Overview
|
The electro-biochemical reactor (EBR) is a patented high-efficiency denitrification, metals, and inorganics removal technology with systems that use proven concepts to provide electrons directly to the EBR as a substitute for using excess nutrients. EBR systems have been proven in third-party technology comparison programs and have been demonstrated to be effective for a broad spectrum of contaminant removals from various mining, power generation and refining wastewaters. EBR systems have been demonstrated to be cost effective, modular format, low-footprint alternatives to conventional bioreactors (CBRs) that require excess nutrients for electron donors and as a consequence, produce large amounts of bio-solids.
The EBR is also a more economical alternative to other treatments such as RO that produce lower volumes but higher concentrated wastes that must be treated further or disposed of in an appropriate manner. EBR systems can be implemented in active and semi-passive configurations, as pump and treat or gravity flow, through the high-surface-area media containing a high-concentration stable biofilm. EBR systems provide electrons directly to the system microbes and use significantly less nutrients, produce effluents very low in bio-solids, while meeting the highest contaminant removal efficiencies and kinetics at high and low temperatures. |
|
Microbes mediate the removal of metal and inorganic contaminants through electron transfer (redox processes). For example, denitrification and Se reduction can be described by the following redox reactions:
The biotransformations shown in reactions 1-2 occur under anaerobic, reductive conditions, and thus require low dissolved oxygen (DO) levels and a negative oxidation-reduction potential (ORP) environment. Five electrons are needed to reduce one molecule of nitrate to nitrogen gas and six electrons to reduce one molecule of selenate to elemental selenium. Other co-contaminants, such as arsenic, cadmium, sulfate, etc., add to the electron demand.
One molecule of glucose, often used as a cost-effective electron donor, can provide up to 24 electrons under complete glucose metabolism (this complete reaction is measured in 10’s of hours). In environmental applications, this efficiency or the number of electrons actually realized is usually considerably less; only a few of these electrons are available within a 4 to 6-hour retention time.
Conventional biological treatment systems supply electrons in the form of excess nutrients added to the system. They require excess nutrients/chemicals to compensate for inefficient and variable electron availability needed to adjust reactor ORP chemistry, compensate for system sensitivity (fluctuation), and to achieve more consistent contaminant removal. These excess nutrients lead to greatly increased biomass production and result in additional CAPEX and OPEX (higher nutrient consumption and management of the excess biomass production).
One molecule of glucose, often used as a cost-effective electron donor, can provide up to 24 electrons under complete glucose metabolism (this complete reaction is measured in 10’s of hours). In environmental applications, this efficiency or the number of electrons actually realized is usually considerably less; only a few of these electrons are available within a 4 to 6-hour retention time.
Conventional biological treatment systems supply electrons in the form of excess nutrients added to the system. They require excess nutrients/chemicals to compensate for inefficient and variable electron availability needed to adjust reactor ORP chemistry, compensate for system sensitivity (fluctuation), and to achieve more consistent contaminant removal. These excess nutrients lead to greatly increased biomass production and result in additional CAPEX and OPEX (higher nutrient consumption and management of the excess biomass production).
ORP STABILITY: A two-stage Conventional Bioreactor (CBR) and a one-stage EBR were used to treat a split sample of the same mining water over a period of 7 months with several water chemistry changes. Both reactors were constructed and operated the same way, using the same retention times. The EBR system was provided ½ the nutrient amounts. Note the ORP stability in the EBR system.
|
The Electro-Biochemical Reactor (EBR) technology overcomes these shortcomings by directly supplying needed electrons to the reactor and microbes, using a low applied potential across the reactor cell (1-3 V) at low milli-Amp levels (the current of 1 mA provides 6.2x10^15 electrons per second). The small amount of power required can even come from a small solar/battery source. These electrons replace and supplement the electrons normally supplied to the conventional bioreactor/microbial system by excess nutrients resulting in considerable OPEX savings and multiple reactor, microbial, and environmental benefits. The directly supplied electrons are readily available to the microbes in a consistent controllable manner without metabolic energy expenditure. Moreover, these “free electrons”, from the microbes’ standpoint, make the EBR bioreactors more robust and less sensitive to wide fluctuations in water chemistries and temperatures than the past generations of conventional biotreatments.
|
The EBR can be implemented in a stand-alone configuration in many situations, but can also be combined with other treatment options for more rigerous wastewater treatment applications. Options are available to convert existing systems to EBRs and reduce bioreactor size or increase the systems treatment capacity, minimize or eliminate use of backwash pumps, and reduce the size of or eliminate filters and presses, thereby significantly reducing operating costs. EBR systems are designed and configured to be mostly self-sufficient and self-regulating with few moving parts. EBR system development moves through a tiered testing program, from bench-level water chemistry and microbial evaluations to site specific bench- and pilot-scale testing to full-scale design and implementation, in order to achieve maximum contaminant removal efficiencies and kinetics. This testing sequence is structured to provide clients assurance that water can be treated and that on-site pilot testing will provide the data required for a successful full-scale implementation of the tested technology. For full-scale implementations, Inotec has collaboration agreements in place with large engineering firms (including Stantec and AMEC) or can partner with a client’s preferred engineering firm to bring an EBR system implementation in on time and budget.
PUBLICATIONS
If you'd like to dig deeper, below is a list of our publications from the last decade, with links wherever possible.
You can also check out the articles published by others on the topic of microbe/electron interactions.
You can also check out the articles published by others on the topic of microbe/electron interactions.
What we've published |
What others have published |
|
|
