Case Study 2

LAB TREATABILITY STUDIES

The sustainable biological treatment solutions iWater implement on-site are highly dependent on verified scientific knowledge and datasets. Therefore, iWater has an in-house laboratory. Worldwide there are numerous examples of failed technology implementations if one omits this crucial step. iWater offers treatability studies as proof of concept to enable informed decision-making for clients.

iWater offers several benchmarked UNBIAS biological treatment systems since iWater consider all chemical, physical, and biological treatment options. iWater also strive to provide cost-effective and sustainable solutions to their clients.

The client can use this tested proof of concept to activate the second phase, to test this concept on a larger scale on-site.   iWater make use of integrated bioreactor systems for this phase.

Examples of useful treatment scenarios include:

The Bioreactor system

The iBiores options include a bioreactor design that ensures effective microbial bioremediation using biological metabolisms for the degradation of specific contamination scenarios. The iBiores systems are offered with remote monitoring and data integration for effective management of real-time treatments. These systems provide faster decision-making tools and quick intelligence for effective 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 environment leads to metal mineral oxidation and excess hydrogen ions (H+) that lowers the pH. There are three significant aspects one needs to address in AMD treatment, firstly one creates sustainable alkalinity, and secondly remove the 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 (customized iron oxidation vessels), iDAS (disperse alkaline substrates (DAS) systems and the iBiores treatments to address the AMD problem.

The iFOV decrease the 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 facilitate the increase of the pH from as low as 2.75 to 7.00, with a low hydraulic retention time, while coupling iDAS to alkalinity creation. This system is an ideal pre-treatment support process for the final biological system.

The iBiorec_AMD system utilizes the dissimilatory sulfate reduction pathways found in sulfate-reducing bacteria (SRB). The SRB catalyzes the conversion of sulfate to hydrogen sulfide (H2S) using various electron donors. The generated hydrogen sulfide will react with many of the metals and create precipitates 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

The iBiorec_lowORP biological system can be supported with several microorganisms that can perform chromium, nitrate, uranium, arsenic, and several other detoxification biotransformations. For example, these microorganisms will treat hexavalent chromium (Cr6+) using reductive metabolisms, even up to 60 mg/ℓ Cr6+ with a residence time of just eight hours.

Nitrogen is a natural part of soil and groundwater. Anthropogenic sources, including agricultural feeding and fertilization, mine blasting and operations, and leakage of untreated sewage, contribute to the contamination of nitrate (NO3), and ammonia (NH3), and even nitrite (NO2) in the environment.

The iBiorec_lowORP biological can treat for all speciation of nitrogen. By creating aerobic conditions, microorganisms oxidize NH4+/ NH3 to NO3(a process called nitrification), while denitrifying bacteria can convert NO3 through NH4+, NH3+ and even to atmospheric nitrogen (N2) under reducing conditions.

Treatability studies have addressed up to 1000 mg/ℓ nitrate while improving the overall release water quality.
Treatability studies have addressed up to 90 mg/ℓ arsenic.
Treatability studies have addressed up to a 30 mg/ℓ uranium.
Treatability studies have addressed up to a 20 mg/ℓ selenium while improving overall release water quality, e.g. pH, hardness and salinity.

Treatability to on-site Implementation

Biological reduction of Cr6+ with the site “trained” indigenous bacteria is a cost-effective treatment option. Bacteria can utilize Cr6+ as terminal electron acceptor (breathing), ultimately releasing the less toxic and insoluble Cr3+ compound. 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 6 hours while also removing more than a 150 mg/ℓ nitrate to yield a water quality re-used in mining operations. Microbial diversity studies support optimization by allowing iWater to “train” the primitive microbial groups to remove these contaminants of concern.

This process can also be utilized 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 will direct the distribution of the donor that allowed Cr6+ to be reduced from ~ 13 mg/ℓ to below detection limit. iWater is proud to report that even after 12 months after the initial infiltration, the Cr6+ levels are still below the detection limit.

Using iWater’s UNBIAS approach to technology evaluation and selection, contamination can be addressed to remove the client’s liability on-site. iWater has also addressed very high concentrations of Cr6+ contamination by injecting the reductant of choice into the site, thereby activating the microbial community.  The community is characterized by molecular tools and internal iWater expertise. BIO-stimulation of the microbes can be considered to start significant reduction of contaminants 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 hydrocarbon contaminated sites.  Iwater also use their in-house treatability studies. The data can be used to design, implement, and operate an on-site 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