Biosorption of heavy metals in a photo-rotating biological contactor—a batch process study

Abstract

Metal removal potential of indigenous mining microorganisms from acid mine drainage (AMD) has been well recognised in situ at mine sites. However, their removal capacity requires to be investigated for AMD treatment. In the reported study, the capacity of an indigenous AMD microbial consortium dominated with Klebsormidium sp., immobilised in a photo-rotating biological contactor (PRBC), was investigated for removing various elements from a multi-ion synthetic AMD. The synthetic AMD was composed of major (Cu, Mn, Mg, Zn, Ca, Na, Ni) and trace elements (Fe, Al, Cr, Co, Se, Ag, Mo) at initial concentrations of 2 to 100 mg/L and 0.005 to 1 mg/L, respectively. The PRBC was operated for two 7-day batch periods under pH conditions of 3 and 5. The maximum removal was observed after 3 and 6 days at pH 3 and 5, respectively. Daily water analysis data demonstrated the ability of the algal-microbial biofilm to remove an overall average of 25-40 % of the major elements at pH 3 in the order of Na > Cu > Ca > Mg > Mn > Ni > Zn, whereas a higher removal (35-50 %) was observed at pH 5 in the order of Cu > Mn > Mg > Ca > Ni > Zn > Na. The removal efficiency of the system for trace elements varied extensively between 3 and 80 % at the both pH conditions. The batch data results demonstrated the ability for indigenous AMD algal-microbial biofilm for removing a variety of elements from AMD in a PRBC. The work presents the potential for further development and scale-up to use PBRC inoculated with AMD microorganisms at mine sites for first or secondary AMD treatment.

Chlorella vulgaris (SAG 211-12) biofilm formation capacity and proposal of a rotating flat plate photobioreactor for more sustainable biomass production

“…Some promising examples of biofilm photobioreactors are those based on rotating systems (Gross et al 2013;Orandi and Lewis 2013;Blanken et al 2014;Gross et al 2015b). The rotating biological contactor (RBC), originally designed for wastewater treatment, has advantages such as the small footprint, low energy consumption, large surface area, and low operational costs.…”

“…The rotating biological contactor (RBC), originally designed for wastewater treatment, has advantages such as the small footprint, low energy consumption, large surface area, and low operational costs. Microalgal systems based on the RBC principle exist in the literature (e.g., PRBC-photorotating biological contactor (Orandi and Lewis 2013) or Algadisk reactor (Blanken et al 2014)), with all of them using disks placed in a horizontal shaft, entering vertically in the tank fluid. A slight exception is the RAB (rotating algal biofilm) reactor described by Gross et al (2013).…”

“…The harvest process, usually by scraping, can also be complicated. Different disk surfaces and coatings were also tested for better biofilm formation (Ozkan et al 2012;Orandi and Lewis 2013;Blanken et al 2014). Nevertheless, further work is needed for future application of this type of reactors by the microalgae industry.…”

Chlorokybophyceae, Klebsormidiophyceae, Coleochaetophyceae

“…Klebsormidium travels through the air and occupies diverse freshwater and terrestrial habitats, including biological soil crusts (Mikhailyuk et al 2015) and urban settings, especially at the base of humid walls and in the shade of tall chimneys (Rindi et al 2008). Some species of Klebsormidium occur in acid mine drainage environments (Brake et al 2014;Novis 2006) and have been proposed for use in removing metals from these environments (Orandi and Lewis 2013). Surveys of biodiversity within Klebsormidium reveal a correlation between phylogeny and particular types of habitat (Mikhailyuk et al 2015).…”

Bioaccumulation of Metals by Algae From Acid Mine Drainage: A Case Study of Frongoch Mine (United Kingdom)

“…Algae can hyperaccumulate metals such as the non-nutrient elements Pb and Cd (Akcali and Kucuksezgin 2011;Diop et al 2016), as well as those with a known nutritional function such as Cu, Zn, and Fe (Orandi and Lewis 2013). Studies have shown that algae present in streams receiving AMD can be used as a bioindicator and bioremediation to infer high concentrations of metals and have the capacity to remove metals from within the watercourse (Al-Homaidan et al 2011;Bwapwa et al 2017).…”