Data set on the bioprecipitation of sulfate and trivalent arsenic by acidophilic non-traditional sulfur reducing bacteria

Data presented here are related to the original paper “Simultaneous removal of sulfate and arsenic using immobilized non-traditional sulfate reducing bacteria (SRB) mixed culture and alternative low-cost carbon sources” published by same authors (Matos et al., 2018) [1]. The data set here presented aims to facilitate this paper comprehension by giving readers some additional information. Data set includes a brief description of experimental conditions and the results obtained during both batch and semi-continuous reactors experiments. Data confirmed arsenic and sulfate were simultaneously removed under acidic pH by using a biological treatment based on the activity of a non-traditional sulfur reducing bacteria consortium. This microbial consortium was able to utilize glycerol, powdered chicken feathers as carbon donors, and proved to be resistant to arsenite up to 8.0 mg L−1. Data related to sulfate and arsenic removal efficiencies, residual arsenite and sulfate contents, pH and Eh measurements obtained under different experimental conditions were depicted in graphical format. Refers to https://doi.org/10.1016/j.cej.2017.11.035


Specifications
Chemistry, Biology, Engineering More specific subject area Biotechnology processes, Bioremediation.

Data format
Analyzed. Averaged data Experimental factors Brief description of any pretreatment of samples

Data source location
Ouro Preto, Brazil Data accessibility All data are included in this document.

Value of the Data
Different experimental conditions were compared. Free and immobilized bacterial cells were used.
Different organic electron donors were tested including some low cost waste material.
Data compare results obtained under batch and semi-continuous experimental conditions. Semi-continuous experiments were carried out for a long time. Data were collected for more than 150 days.
Arsenite (bio)precipitation by sulfate reducing microorganisms was achieved under acidic pH.

Data
Data described simultaneous SO 4 2− and As(III) removal obtained by using a non-traditional SRB microbial consortium previously adapted to the growth under acidic pH using Glycerol and PCF as electron donors. The main bacterial species identified are: Pantoea agglomerans, Enterobacter sp., Citrobacter sp., Cupriavidus metallidurans, Ralstonia sp. and Burkholderia cepacia. Arsenic and sulfate are commonly found as contaminants in industrial effluents from mining and metallurgical industries. Arsenic and sulfate removal were obtained under batch and semi-continuous culture conditions. Semi-continuous up-flow reactors were constructed and operated for more than 150 days to prove their efficiency. At the final, effluent pH was neutralized and, depending on the operational conditions, SO 4 2− and As(III) ions were removed with 74.8% and 80% efficiency, respectively.

Batch experiments
Data presented in Figs. 1-4 are referred to experimental conditions summarized in Table 1.

Experimental design, materials, and methods
Experimental design is detailed in Matos et al. [1]. All experiments and analyses were replicated twice and data were averaged.

Microbial consortium
A microbial culture was obtained after enrichment of some sediment samples, collected from an urban pond, using modified Postgate C liquid medium [1,2]. Microbial culture was adapted to acidic pH (5-5.5) and to the use of Glycerol as electron donor. Main identified microbial species were Pantoea agglomerans, Enterobacter sp, Citrobacter sp; Cupriavidus metallidurans, Ralstonia sp and Burkholderia cepacia [1]. Microbial mixed culture was considered as a non-traditional sulfate reducing bacteria (SRB) consortium.

Culture parameters
Microbial growth and process efficiency were indirectly estimated by measuring arsenic and sulfate contents and pH and Eh (mV) changes as well. Both, batch and semi-continuous experiments were conducted using free and calcium alginate encapsulated microbial cells [1]. Postgate C liquid medium, at pH 5.5 was enriched with sodium lactate, glycerol and PCF as carbon sources. Culture medium pH was acidified to pH 5.5. Microbial tolerance to arsenic (4.0 and 8.0 mg of As(III) L −1 ) was accessed.

Batch experiments
Chemical oxygen demand (COD)-to-sulfate ratio used were 2.5 or 3.0, using sodium lactate or glycerol as main soluble carbon sources, respectively. Cultures were incubated in sterilized glass bottles (Postgate B medium, 473 mL, pH 5.0) containing a 5% (w v −1 ) inoculum, PCF (2%) and 4.0 or 8.0 mg L −1 of As(III). An abiotic control flask was also compared. Flasks were sealed to minimize    Oxygen dissolution and incubated at 35°C for 360 h. 2 mL aliquots were withdrawn for residual sulfate concentration, pH and Eh measurements. Initial and final As(III) concentration were determined.

Semi-continuous experiments
Four glass bioreactors (Fig. 7) were constructed as described by Matos et al. [1]. Bioreactors were supplied with Postgate C medium and inoculated with microbial consortium adapted to different electron donors and pH values. Sodium lactate and PCF (PCFF, CONV), glycerol and immobilized PCF (PCFI 1, PCFI 2, CONV) and free PCF (PCFF) were tested as carbon sources. Free (PCFF, CONV) or encapsulated (PCFI 1, PCFI 2) microbial cells were inoculated into the systems. Additionally, the suitability of using tap water (PCFI 1) instead of purified water (PCFF, PCFI 2, CONV) was tested. Operating temperature was 347 2°C and bioreactors were supplied by an up-flow flux. Monitored parameters were pH, oxidation/reduction potential (Eh), residual sulfate and As(III) concentration. Bioreactors were operated during more than 150 days.