Wine wastes as carbon source for biological treatment of acid mine drainage

Use of propionic acid additions to enhance zinc removal from mine drainage in short residence time, flow-through sulfate-reducing bioreactors

The effectiveness of liquid carbon additions to enhance zinc removal in laboratory-scale short hydraulic residence time (19 h) compost bioreactors receiving synthetic mine water with a high influent zinc concentration (45 mg/L) was investigated. Effective removal of such elevated zinc concentrations could not be sustained by sulfate reduction and/or other attenuation processes without carbon supplementation. Propionic acid addition resulted in improved and sustained performance by promoting the activities of sulfate reducing bacteria, leading to efficient zinc removal (mean 99%) via bacterial sulfate reduction. In contrast, cessation of propionic acid addition led to carbon limitation and the growth of sulfur oxidising bacteria, compromising zinc removal by bacterial sulfate reduction. These research findings demonstrate the potential for modest liquid carbon additions to compost-based passive treatment systems to engineer microbial responses which enhance rates of zinc attenuation in a short hydraulic residence time, enabling remediation of highly polluting mine drainage at sites with limited land availability.

Use of lignocellulosic waste materials in the passive treatment of highly alkaline wastewater contaminated with sulfates and metals - From a laboratory study to pilot scale

Passive wastewater treatment systems are an alternative to costly and ineffective chemical wastewater treatment methods. Lignocellulosic waste materials (LWM) are often used in passive wastewater treatment systems as a cheap and accessible source of nutrients. LWM, such as spent mushroom compost and woodchips, have been implemented for the successful management of mildly alkaline effluents, which constitute a large fraction of industrial wastewater. The objective of the study was to provide an extensive study of the parameters in four types of commonly used LWM (raw and composted sawdust, spent mushroom compost and woodchips), which can be used in the planning of a passive wastewater treatment plant. LWM were shown to remove up to 90% Zn²⁺ and Pb²⁺ from a model solution and neutralize wastewater. Moreover, the LWM were inhabited by a physiologically diverse microbial consortium containing sulfate-reducing and cellulolytic microbes, which can influence the treatment process. Another purpose of this study was to construct a pilot wastewater treatment plant based on the use of LWM and gravel and to present its ability to effectively treat extremely alkaline flotation wastewater (pH = 12) originating from a lead and zinc mine located in Montenegro. The treated wastewater had a unique, but challenging chemical composition for passive treatment, as it was heavily contaminated with sulfates (∼1200 mg/L) and lead (∼1 g/L). The removal within the developed installation reached a rate of 66%, while the treated effluent, after initial neutralization, was maintained at a pH of approximately 7. Lead and zinc concentrations after treatment were also kept at levels required by Montenegrin law for wastewater disposal.

Sulfate removal rate and metal recovery as settling precipitates in bioreactors: Influence of electron donors

Four down-flow structured bed bioreactors were operated targeting biological sulfate-reduction and metal recovery. Three different electron donors were tested: glycerol (R1), lactate (R2), sucrose (R3), and a blend of the previous three (R4) with an increasing copper influent load (5, 15, and 30 mg Cu²⁺.L^-1). Copper inhibited sulfate-reduction in R1 (15 mg Cu²⁺.L^-1) and R3 (5 mg Cu²⁺.L^-1), but the fermentative activity was not affected. R2 and R4 were not inhibited by the copper influent concentration. R2 provided the highest sulfate reduction rate (1767.3 ± 240.1 mg SO₄^2-.L.day^-1). Nonetheless, the accumulation of settling precipitates was 22 % higher in R4 than in R2, indicating the former yielded the highest metal recovery as settling precipitates (24.8 g FSS.L^-1, 25 % Fe²⁺, 5% Cu²⁺). 16S rRNA sequencing showed highest diversity of sulfate-reducing bacteria in R2. A predominance of sulfate-reducing and fermentative bacteria with more similarity was observed between microbial populations in R1 and R4, despite the difference in toxicity thresholds. Hence, the electron donor influenced not only the biological sulfate reduction, but also metal toxicity thresholds and metal recovery as settling precipitates.

Development of a process for microbial sulfate reduction in cold mining waters - Cold acclimation of bacterial consortia from an Arctic mining district

Biological sulfate removal is challenging in cold climates due to the slower metabolism of mesophilic bacteria; however, cold conditions also offer the possibility to isolate bacteria that have adapted to low temperatures. The present research focused on the cold acclimation and characterization of sulfate-reducing bacterial (SRB) consortia enriched from an Arctic sediment sample from northern Finland. Based on 16S rDNA analysis, the most common sulfate-reducing bacterium in all enriched consortia was Desulfobulbus, which belongs to the δ-Proteobacteria. The majority of the cultivated consortia were able to reduce sulfate at temperatures as low as 6 °C with succinic acid as a carbon source. The sulfate reduction rates at 6 °C varied from 13 to 42 mg/L/d. The cultivation medium used in this research was a Postgate medium supplemented with lactate, ethanol or succinic acid. The obtained consortia were able to grow with lactate and succinic acid but surprisingly not with ethanol. Enriched SRB consortia are useful for the biological treatment of sulfate-containing industrial wastewaters in cold conditions.

Evaluation of fine organic mixtures for treatment of acid mine drainage in sulfidogenic reactors

The performance of passive biochemical reactors in acid mine drainage (AMD) treatment could be enhanced by using fine organic substrates in new reactor designs, such as diffusive exchange reactors. This work evaluated the effect of fine cellulosic components in organic mixtures and of enrichment with inoculum, on sulfate and metals removal in discontinuous cultures for three types of synthetic AMD. The cellulosic substrates evaluated were sawdust, microcrystalline cellulose, and forestry cellulose fibers, supplemented with cow manure and leaf compost. Using microcrystalline cellulose and forestry cellulose fibers with the less concentrated AMD, high sulfate reduction rates (73 mg/L-d and 58.2 mg/L-d, respectively) were achieved. Correspondingly, iron concentrations were reduced by 69% and 86.6%. Based on their higher sulfate reducing capacity, cellulose fibers obtained as fiber boards from a local kraft pulp mill were selected for treating a synthetic AMD with a high copper concentration (273 mg/L) and pH 4.94. In batch culture, low sulfate reducing activity (13.10 mg/L-d) was only observed at the highest substrate/AMD ratio (0.5:10) tested. Results show that the use of forestry cellulose fibers in reactive mixtures supplemented with inoculum could be an alternative for optimization of diffusive exchange reactors for AMD treatment.

Optimization of the operation of packed bed bioreactor to improve the sulfate and metal removal from acid mine drainage

The present study discusses the potentiality of using anaerobic Packed Bed Bioreactor (PBR) for the treatment of acid mine drainage (AMD). The multiple process parameters such as pH, hydraulic retention time (HRT), concentration of marine waste extract (MWE), total organic carbon (TOC) and sulfate were optimized together using Taguchi design. The order of influence of the parameters towards biological sulfate reduction was found to be pH > MWE > sulfate > HRT > TOC. At optimized conditions (pH - 7, 20% (v/v) MWE, 1500 mg/L sulfate, 48 h HRT and 2300 mg/L TOC), 98.3% and 95% sulfate at a rate of 769.7 mg/L/d. and 732.1 mg/L/d. was removed from the AMD collected from coal and metal mine, respectively. Efficiency of metal removal (Fe, Cu, Zn, Mg and Ni) was in the range of 94-98%. The levels of contaminants in the treated effluent were below the minimum permissible limits of industrial discharge as proposed by Bureau of Indian Standards (IS 2490:1981). The present study establishes the optimized conditions for PBR operation to completely remove sulfate and metal removal from AMD at high rate. The study also creates the future scope to develop an efficient treatment process for sulfate and metal-rich mine wastewater in a large scale.

Biological synthesis of nanosized sulfide semiconductors: current status and future prospects

There have been extensive and comprehensive reviews in the field of metal sulfide precipitation in the context of environmental remediation. However, these works have focused mainly on the removal of metals from aqueous solutions-usually, metal-contaminated effluents-with less emphasis on the precipitation process and on the end-products, frequently centering on metal removal efficiencies. Recently, there has been an increasing interest not only in the possible beneficial effects of these bioremediation strategies for metal-rich effluents but also on the formed precipitates. These metal sulfide materials are of special relevance in industry, due to their optical, electronic, and mechanical properties. Hence, identifying new routes for synthesizing these materials, as well as developing methodologies allowing for the control of the shape and size of particulates, is of environmental, economic, and practical importance. Multiple studies have shown proof-of-concept for the biological synthesis of inorganic metallic sulfide nanoparticles (NPs), resorting to varied organisms or cell components, though this information has scarcely been structured and compiled in a systematic manner. In this review, we overview the biological synthesis methodologies of nanosized metal sulfides and the advantages of these strategies when compared to more conventional chemical routes. Furthermore, we highlight the possibility of the use of numerous organisms for the synthesis of different metal sulfide NPs, with emphasis on sulfate-reducing bacteria (SRB). Finally, we put in perspective the potential of these methodologies in the emerging research areas of biohydrometallurgy and nanobiotechnology for the uptake of metals in the form of metal sulfide nanoparticles. A more complete understanding of the principles underlying the (bio)chemistry of formation of solids in these conditions may lead to the large-scale production of such metal sulfides, while simultaneously allowing an enhanced control over the size and shape of these biogenic nanomaterials.

Preparation of metal-resistant immobilized sulfate reducing bacteria beads for acid mine drainage treatment

Novel immobilized sulfate-reducing bacteria (SRB) beads were prepared for the treatment of synthetic acid mine drainage (AMD) containing high concentrations of Fe, Cu, Cd and Zn using up-flow anaerobic packed-bed bioreactor. The tolerance of immobilized SRB beads to heavy metals was significantly enhanced compared with that of suspended SRB. High removal efficiencies of sulfate (61-88%) and heavy metals (>99.9%) as well as slightly alkaline effluent pH (7.3-7.8) were achieved when the bioreactor was fed with acidic influent (pH 2.7) containing high concentrations of multiple metals (Fe 469 mg/L, Cu 88 mg/L, Cd 92 mg/L and Zn 128 mg/L), which showed that the bioreactor filled with immobilized SRB beads had tolerance to AMD containing high concentrations of heavy metals. Partially decomposed maize straw was a carbon source and stabilizing agent in the initial phase of bioreactor operation but later had to be supplemented by a soluble carbon source such as sodium lactate. The microbial community in the bioreactor was characterized by denaturing gradient gel electrophoresis (DGGE) and sequencing of partial 16S rDNA genes. Synergistic interaction between SRB (Desulfovibrio desulfuricans) and co-existing fermentative bacteria could be the key factor for the utilization of complex organic substrate (maize straw) as carbon and nutrients source for sulfate reduction.

Cu retention in an acid soil amended with perlite winery waste

The effect of perlite waste from a winery on general soil characteristics and Cu adsorption was assessed. The studied soil was amended with different perlite waste concentrations corresponding to 10, 20, 40 and 80 Mg ha(-1). General soil characteristics and Cu adsorption and desorption curves were determined after different incubation times (from 1 day to 8 months). The addition of perlite waste to the soil increased the amounts of organic matter as well as soil nutrients such as phosphorus and potassium, and these increments were stable with time. An increase in Cu adsorption capacity was also detected in the perlite waste-amended soils. The effect of perlite waste addition to the soil had special relevance on its Cu adsorption capacity at low coverage concentrations and on the energy of the soil-Cu bonds.

Improvement of the degradation of sulfate rich wastewater using sweetmeat waste (SMW) as nutrient supplement

External dosing of sweetmeat waste (SMW) dosing into exhausted upflow packed bed bioreactor (PBR) resulted in prompt reactivation of SO4(2-) removal. Different SMW concentrations in terms of chemical oxygen demand (COD)/SO4(2-) ratios (1, 2, 4 and 8) were introduced into four identical PBR where process stability was found within 3 weeks of operation. SO4(2-) removal was proportional to COD/SO4(2-) ratios up to 4 at which maximum sulfate removal (99%) was achieved at a rate of 607 mg/d. The value of COD consumption:SO4(2-)removal was much higher at ratio 4 than 8 whereas, ratio 2 was preferred over all. Net effluent acetate concentration profile and total microbial population attached to the reactor matrices were corresponding to COD/SO4(2-) ratio as 4>8>2>>1. Sulfate reducing bacteria (SRB) population was found to be inversely proportional to COD/SO4(2-) ratio in which acetate oxidizing SRB and fermentative bacteria were the dominant.

Sulfate reduction in sulfuric material after re-flooding: Effectiveness of organic carbon addition and pH increase depends on soil properties

Sulfuric material is formed upon oxidation of sulfidic material; it is extremely acidic, and therefore, an environmental hazard. One option for increasing pH of sulfuric material may be stimulation of bacterial sulfate reduction. We investigated the effects of organic carbon addition and pH increase on sulfate reduction after re-flooding in ten sulfuric materials with four treatments: control, pH increase to 5.5 (+pH), organic carbon addition with 2% w/w finely ground wheat straw (+C), and organic carbon addition and pH increase (+C+pH). After 36 weeks, in five of the ten soils, only treatment +C+pH significantly increased the concentration of reduced inorganic sulfur (RIS) compared to the control and increased the soil pore water pH compared to treatment+pH. In four other soils, pH increase or/and organic carbon addition had no significant effect on RIS concentration compared to the control. The RIS concentration in treatment +C+pH as percentage of the control was negatively correlated with soil clay content and initial nitrate concentration. The results suggest that organic carbon addition and pH increase can stimulate sulfate reduction after re-flooding, but the effectiveness of this treatment depends on soil properties.

Oxidation of sulphide in abandoned mine tailings by ferrate

In this study, Fe(VI) was applied to treat three mine tailings containing different amounts of sulphides and heavy metals. Oxidation of sulphides by Fe(VI) was studied at pH 9.2 with variation of solid to solution ratio, Fe(VI) concentration and injection number of Fe(VI) solution. The major dissolved products from the treatment of mine tailings with Fe(VI) solution were sulphate and arsenic. Oxidation efficiency of sulphides was evaluated by reduction efficiency of Fe(VI) as well as by measurement of dissolved sulphate concentration. Even though inorganic composition of three mine tailings was different, reduction fraction of Fe(VI) was quite similar. This result can suggest that Fe(VI) was involved in several other reactions in addition to oxidation of sulphides. Oxidation of sulphides in mine tailing was greatly dependent on the total amount of sulphides as well as kinds of sulphides complexed with metals. Over the five consecutive injections of Fe(VI) solution, dissolved sulphate concentration was greatly decreased by each injection and no more dissolved sulphate was observed at the fifth injection. While dissolved arsenic was decreased lineally up to the fifth injection. Sulphate generation was slightly increased for all mine tailings as Fe(VI) concentration was increased; however, enhancement of oxidation efficiency of sulphides was not directly proportional to the initial Fe(VI) concentration.

Biological treatment of acidic coal refuse using sulphate-reducing bacteria with chicken manure as carbon source

The performance of using chicken manure as carbon source to promote sulphate-reducing bacteria (SRB) activity within acidic coal refuse to prevent the generation of acidic leachate was investigated in batch and column bioreactors. The bioreactors showed satisfactory performance in biological sulphate reduction, evidenced by the increase in effluent pH, high removal efficiencies of sulphate and metals, and the presence of large numbers of SRB. Scanning electron microscope-energy dispersive spectrometry (EDS) analysis of the formed precipitate indicated the formation of metal sulphides. Chicken manure was observed to play an important role in this treatment, which could not only provide carbon source but also reduce the adverse effect of strong acidity and metal toxicity on SRB activity. Metal removal could be mainly attributed to sulphides precipitation and sorption to chicken manure. This study indicated that SRB with chicken manure could be a novel alternative used for the prevention of acidic leachate from coal refuse.

Utilization of makgeolli sludge filtrate (MSF) as low-cost substrate for bacterial cellulose production by Gluconacetobacter xylinus

Search for efficient low-cost substrate/additives are gaining significant impetus in bacterial cellulose (BC) production. Makgeolli sludge (a traditional Korean wine distillery waste) is enriched with organic acid, alcohol, and sugar. Using makgeolli sludge filtrate (MSF) and Hestrin-Schramm (HS) medium (g/l of distilled water: glucose, 10.0; peptone, 5.0; yeast extract, 5.0; disodium phosphate, 2.7; citric acid, 1.15; pH 5.0), two different media-namely the modified HS media (ingredients of HS media except glucose dissolved in MSF) and mixed modified HS media (equal volume mixture of original and modified HS media)-were formulated. BC production with Gluconacetobacter xylinus was studied using the two above referred medium. Keeping HS medium as reference, effect of initial pH, glucose, ethanol, and organic acid concentration on BC production was also studied. It suggests that increasing initial glucose (up to 25 g/l) though improves BC production but results in poor BC yield above 15 g/l of glucose. However, addition of alcohol (up to 1%v/v) or citric acid (up to 20 mM) escalate productivity up to four and two times, respectively. In both modified HS media and mixed modified HS medium, BC production was four to five times higher than that of original HS medium. Even MSF alone surpassed HS medium in BC production. Scanning electron microscopy showed that BC microfibrils from MSF based media were several micrometers long and about 25-60 nm widths. X-ray diffraction patterns suggested the produced BC were of cellulose I polymorph.

Simultaneous removal of nitrate and sulfate from greenhouse wastewater by constructed wetlands

This study evaluated the effectiveness of C-enriched subsurface-flow constructed wetlands in reducing high concentrations of nitrate (NO) and sulfate (SO) in greenhouse wastewaters. Constructed wetlands were filled with pozzolana, planted with common cattail (), and supplemented as follows: (i) constructed wetland with sucrose (CW+S), wetland units with 2 g L of sucrose solution from week 1 to 28; (ii) constructed wetland with compost (CW+C), wetland units supplemented with a reactive mixture of compost and sawdust; (iii) constructed wetland with compost and no sucrose (CW+CNS) from week 1 to 18, and constructed wetland with compost and sucrose (CW+CS) at 2 g L from week 19 to 28; and (iv) constructed wetland (CW). During 28 wk, the wetlands received a typical reconstituted greenhouse wastewater containing 500 mg L SO and 300 mg L NO. In CW+S, CW+C, and CW+CS, appropriate C:N ratio (7:3.4) and redox potential (-53 to 39 mV) for denitrification resulted in 95 to 99% NO removal. Carbon source was not a limiting factor for denitrification in C-enriched constructed wetlands. In CW+S and CW+CS, the dissolved organic carbon (DOC)/SO ratios of 0.36 and 0.28 resulted in high sulfate-reducing bacteria (SRB) counts and high SO removal (98%), whereas low activities were observed at DOC/SO ratios of 0.02 (CW) to 0.11 (CW+C, CW+CNS). On week 19, when organic C content was increased by sucrose addition in CW+CS, SRB counts increased from 2.80 to 5.11 log[CFU+1] mL, resulting in a level similar to the one measured in CW+S (4.69 log[CFU+1] mL). Consequently, high sulfate reduction occurred after denitrification, suggesting that low DOC (38-54 mg L) was the limiting factor. In CW, DOC concentration (9-10 mg L) was too low to sustain efficient denitrification and, therefore, sulfate reduction. Furthermore, the high concentration of dissolved sulfides observed in CW+S and CW+CS treated waters were eliminated by adding FeCl.

Application of ferrate for the treatment of metal-sulfide

Fe(VI) was evaluated to treat metal-sulfides such as Fe-S, Pb-S, Cu-S and Cd-S contained in mine tailings known to generate acidic mine drainages. The rate of Fe(VI) reduction was dependent on the type of metal-sulfide as well as the concentration of each metal-sulfide. Fe(VI) reduction increased as the concentration of each metal-sulfide increased. The order of initial rates for the Fe(VI) reduction was Pb-S > Cu-S > Fe-S > Cd-S. The rate of Fe(VI) reduction by each metal sulfide increased as the ionic strength increased. For all metal sulfides, reduction efficiency of Fe(VI) was not affected by the presence of different background electrolytes except NaNO(2) and Na(2)SO(3). This result suggests that fully oxidized anions such as [Formula: see text] , [Formula: see text] , [Formula: see text] as well as redox insensitive anion such as Cl(-) are not involved in the redox reaction between Fe(VI) and metal sulfides.

Biotreatment of Cr(VI) contaminated waters by sulphate reducing bacteria fed with ethanol

Biological treatment of Cr(VI) contaminated waters was performed in fixed bed reactors inoculated with SRB (sulphate-reducing bacteria) growing on ethanol. Treatment efficiency was evaluated by checking chemical abatement of Cr(VI) and by ecotoxicological tests using the nematode Caenorhabditis elegans. A preliminary comparison between ethanol and lactate was performed, denoting that using ethanol, the same values of final sulphate abatement were obtained. In addition ethanol showed to be a substrate more competitive than lactate in kinetic terms. Fixed bed column reactors were continuously fed with a solution containing sulphates (3 g L(-1)), ethanol (1.5 g L(-1)) and Cr(VI) (50 mg L(-1)). At steady state the column inoculated with SRB removed 65 ± 5% of sulphate and 95 ± 5% of chromium. Bioactive removal mechanisms predominated over biosorption. Diminution of Cr(VI) toxicity was assessed by using the nematode C. elegans as a test organism showing that the survival of nematodes was 20% in the presence of the untreated influent and raised up to 53% when the nematodes were exposed to the treated effluent.