The Bioreactor system

The iBiores options include a bioreactor design that ensures effective microbial bioremedial solutions utilising biological metabolisms for the degradation of specific contamination scenarios. iBiores systems are coupled with remote monitoring and data integration for effective management of real-time treatments. This provides faster decision-making tools and quick intelligence for site responses.

Examples of effective treatment scenarios include Acid/alkaline mine drainage (AMD).

Acid/alkaline mine drainage is a common environmental risk generated by coal, gold, and metal mining industries. Acid drainages are often rich in sulfate – (SO42-) and metal minerals (e.g. Al, Fe, Mn). Oxidation of the water leads to metal mineral oxidation and the release of hydrogen ions (H+) that lowers the pH. The three major aspects to address in the effective treatment of AMD is the creation of sustainable alkalinity while removing excess concentrations of sulfate and metals in the water, that can be harmful for human and animal consumption.

iWater already has a compelling combination using iFOV (customised iron oxidation vessels), iDAS (disperse alkaline substrates (DAS) systems), and the iBiores treatments to address the AMD conundrum. This is a unique one-pot process.

The iFOV decrease ferrous iron, for example, from 150 mg/ℓ Fe2+ to 0.5 mg/ℓ with a short retention time.

The iDAS systems are customer-specific but can expand the pH increase from 2.75 to 7.02 with a hydraulic retention time of just two hours. This is coupled to alkalinity creation of up to 672 CaCO3/ℓ. This system is ideal as a pre-treatment support for biological systems.

The iBiorec_AMD system utilises the dissimilatory sulfate reduction pathways found in SRB. SRB catalyses the conversion of sulfuric acid to hydrogen sulfide (H2S) using electron donors. The generated hydrogen sulfide will react with any remaining metals and precipitate as insoluble metal sulfides. The exclusive SRB consortia used by iWater can reduce sulfate concentrations up to 3 000 mg/ℓ to below 200 mg/ℓ with a retention time as low as 24 hours.

Anaerobic iBioRes systems that address excess metals and sulfate concentrations

The iBiorec_lowORP biological system can be inoculated with several microorganisms that have the capability to perform chromium, nitrate, uranium, arsenic, and several other detoxification biotransformations. For example, these microorganisms will treat hexavalent chromium (Cr6+) using reductive metabolisms. Published treatability, that will address up to 60 mg/ℓ Cr6+ reduction with a residence time of just eight hours, has been showcased.

Nitrogen is a natural part of soil and groundwater. Anthropogenic sources, including agricultural feeding and fertilisation, animal debris, mine blasting and operations, and leakage of untreated sewage, contribute majorly to the contamination of nitrate (NO3-), with a lesser amount of ammonium (NH4+), ammonia (NH3), and nitrite (NO2-).

The iBiorec_lowORP biological can be used for treatment for all speciation of nitrogen. By creating aerobic conditions, microorganisms oxidise NH4+/ NH3 to NO3- (a process of nitrification). On the contrary, denitrifying bacteria can convert NO3- through NH4+, NH3+ to atmospheric nitrogen (N2) under reducing circumstances as an effective treatment option.

Treatability to site Implementation

Biological reduction of Cr6+ with site trained indigenous bacteria is a cost-effective treatment option. Bacteria can utilise Cr6+ as terminal electron acceptor (breathing), ultimately releasing the less toxic and insoluble Cr3+ compounds. Each treatment system is based on a tremendous amount of knowledge generated in the iWater in-house laboratory.

Hexavalent chromium contamination (~ 10 mg/ℓ), from a chromium smelter in North West Province, South Africa, was successfully treated from groundwater. The indigenous microbial diversity treated the Cr6+ to below detection limit with a retention time of just six hours while also addressing more than a 150 mg/ℓ nitrate in the reuse water quality. Microbial diversity studies support optimisation by allowing iWater to train the primitive microbial groups to remove these contaminants of concern.

This process can also be utilised effectively with in-situ bioremediation (iBiorec_IS) by activating the indigenous microbes with bioremedial compounds like emulsified vegetable oil (EVO) and proprietary supplements, thereby stimulating the degradation. Tracer studies confirmed the flow/distribution of donor that allowed Cr6+ to be reduced from ~ 13 mg/ℓ to below detection limit once a steady state was reached. Twelve months (one year) after the initial infiltration, without any supplemented dosing, the Cr6+ levels are still below the detection limit.

Using iWater’s UNBIAS approach to technology evaluation and selection, it was also considered to integrate in-situ bioremediation with intense chemical reductant pre-treatments. In a high Cr6+ contamination scenario, reductant was injected into the site, and microbial community impact followed using the molecular tools and expertise iWater hosts. After that, the microbes could be stimulated to regain capabilities using iWater’s scientific knowledge to start significant reduction within a few weeks.

Other treatment options include Hydrocarbon degradation or physical treatment options.

iWater’s small-scale iH-cell can showcase a treatment option for a variety of hydrocarbon contaminated materials, as an option in the in-house treatability studies. This data can be used to design, implement, and operate an onsite treatment plant, to empower each client’s decision-making to implement a successful and sustainable treatment option. 

For more information, contact iWater at 072 786 2814 or send an email to info@iwatersolutions.co.za