Introducing heterotrophic iron ore bacteria as new candidates in promoting the recovery of e-waste strategic metals.

Electrical instruments are an integral part of human life resulting in a vast electronic waste generation (74.7 Mt by 2030), threatening human life and the environment due to its hazardous nature. Therefore, proper e-waste management is a necessity. Currently, bio-metallurgy is a sustainable process and an emerging research field. Simultaneous leaching of metals using two groups of indigenous heterotrophs and autotrophs was an exciting work done in this study. Bioleaching experiments using pre-adapted cultures were investigated at three e-waste densities: 5, 10, and 15 g/L. Statistical analysis was done using two-way ANOVA. Copper (93%), zinc (21.5%), and nickel (10.5%) had the highest recovery efficiencies. There was a significant difference between copper, nickel, tin, and zinc concentrations and the bacterial group (P < 0.05); Iron-oxidizing bacteria showed the most weight decrease and recovered 46-47% of total metals, mainly copper and nickel, while sulfur oxidizers were more capable of zinc leaching. The heterotrophs solubilized tin preferably and substantially decreased e-waste weight. Using heterotrophs alongside autotrophs is proposed to promote metal recovery.

Remediation of metals and plastic from e-waste by iron mine indigenous acidophilic bacteria.

The growing consumption of electrical and electronic equipment leads to high amounts of electronic waste (e-waste), which is now considered the fastest-growing waste stream at the national and international levels. As well as being a potential secondary resource due to its precious metals content, e-waste also contains strategic metals and plastics. For instance, mobile phones have about 25-55% plastic substances. A few studies have been performed to investigate the potential of indigenous bacteria in metals' bioleaching from the polluted environment. Heterotrophic bioleaching potential in acidic conditions had been preliminarily investigated. Two soil types of iron ore were considered the source of indigenous bacteria. Despite the acidophilic nature of the bacterial consortium, they continued their leaching activity regardless of alkaline conditions. Maximum biorecovery rate related to copper (4%) responding to the main soil, owing to the higher copper content of mobile phone waste. Chromium had the least recovery rate (⩽0.002%). Overall, the maximum metal recovery rate was 4.7%, achieved by tailing heterotrophs at an e-waste loading of 10 g l-1. Statistical analysis had shown that there was no significant difference between the metal recovery rates and soil type or even the solid-liquid ratio (p > 0.05). Although acidophilic indigenous heterotrophs could not be an appropriate alternative for a large amount of metal recovery process, they might have considerable potential in the bioremediation of e-waste plastic fractions and metals in low concentrations simultaneously.

Indigenous bacteria as an alternative for promoting recycled paper and cardboard mill wastewater treatment.

The present study aimed to investigate indigenous bacteria possibility in recycled paper and cardboard mill (RPCM) wastewater treatment through the isolation and identification of full-scale RPCM indigenous bacteria. The molecular characterization of the isolated bacteria was performed by 16S rRNA gene sequencing. Klebsiella pneumoniae AT-1 (MZ599583), Citrobacter freundii AT-4 (OK178569), and Bacillus subtilis AT-5 (MZ323975) were dominant strains used for RPCM wastewater bioremediation experiments. Under optimal conditions, the maximum values of chemical oxygen demand (COD) and color biodegradation by C. freundii AT-4 were 79.54% and 43.81% after 10 days of incubation, respectively. In the case of B. subtilis strain AT-5 and K. pneumoniae AT-1, the maximum values of COD and color biodegradation were 70.08%, 45.96%, 71.26%, and 32.06%, respectively. The results from optimal conditions regarding efficiency were higher in comparison with the efficiency obtained from the oxidation ditch treatment unit in full-scale RPCM-WWTP. Therefore, the present study introduces the isolated indigenous bacteria strains as a promising candidate for improving the RPCM-WWTP efficiency using bioremediation.

Data on airborne bacteria and fungi emission from a conventional hospital wastewater treatment plant.

The lack of necessary air pollution control measures in the construction of hospital wastewater treatment plants results in the release of harmful bioaerosols in and around the hospital. A sampling of airborne bacteria and fungi was performed using the gravitational method in 9 sites including an upwind site, intra-plant and outside a hospital wastewater treatment plants with activated sludge technology in Tehran (1, 5 and 3 points, respectively) from March to June. Bioaerosol on nutrient agar media were identified quantitatively and qualitatively. Intra-plant airborne particulate matter concentrations were measured by an optical particle sizer in intervals of 6 s for 60 min. The environmental parameters were also recorded in the sampling period. Experimental data was collected and analyzed by Excel software and SPSS statistical software version 23, respectively. This work is useful to help manage bioaerosols exposure risk such as WWTP.

Data on biosurfactant assisted removal of TNT from contaminated soil.

Contamination of environment, especially soil, is in great concern and can cause health problems. Thus, remediation of these pollutants through environmentally friendly methods should be considered. The aim of this data was bioremediation of TNT from contaminated soil. Two plastic pans were used as bioreactor. In each pan, 3 kg of soil was used. Concentration of TNT in contaminated soil was 1000 mg/kg. Rhamnolipid in concentration of 60 mg/l was added to intended pan. Sampling was done in each two weeks. In order to assessment of TNT degradation, samples were analyzed with HPLC. The data showed that after 154 days of experiment, TNT removal in soil that amended with rhamnolipid was 73% and in experiment with no addition of rhamnolipid was 58%. Based on the obtained data rhamnolipid was effective in remediation of TNT contaminated soil.

Kinetic parameters and nitrate, nitrite changes in bioremediation of Toxic Pentaerythritol Tetranitrate (PETN) contaminated soil.

BACKGROUND: Cleanup of areas contaminated by explosives is a public health concern. Some explosives can be carcinogenic in humans. Pentaerythritol Tetranitrate (PETN), a powerful explosive with very low water solubility, can be easily transported to ground waters. OBJECTIVE: This study was conducted to determine the removal efficiencies of PETN from soil by bioremediation, and obtain kinetic parameters of biological process. METHODS: This experimental study was conducted at the Environmental Health Engineering Lab (Isfahan University of Medical Sciences, Isfahan, Iran) in 2015-2016. In the present work, bioremediation of the explosive-polluted soils by PETN in anaerobic-aerobic landfarming method was performed. The influence of seeding and biosurfactant addition on bioremediation was also evaluated. The data were analyzed using Microsoft Excel software. RESULTS: The results show that, as the initial concentration of PETN increased, the lag phase was increased and the specific growth rate was increased up to 0.1/day in concentration of 50 mg/kg, and then it was decreased to 0.04/day. Subsequent decreases in specific growth rate can cause substrate inhibition. Seeding causes decrease in lag phase significantly. Biosurfactant addition had little to no impact on the length of lag phase, but biosurfactant plus seeding can increase the growth rate to 0.2/day, however, inhibitory effect of the initial concentration was started in very high concentration of PETN (150 mg/kg). CONCLUSION: Biosurfactant addition and seeding together have an impressive effect on biodegradation of PETN, furthermore seeding can enhance active microbial consortium and biosurfactant can improve the poor aqueous solubility of PETN, therefore making the substrate more accessible.