Henry H. Tabak

Advances in biotreatment of acid mine drainage and biorecovery of metals: 1. Metal precipitation for recovery and recycle.

Acid mine drainage (AMD), an acidic metal-bearingwastewater, poses a severe pollution problem attributedto post mining activities. The metals usuallyencountered in AMD and considered of concern for riskassessment are arsenic, cadmium, iron, lead, manganese,zinc, copper and sulfate. The pollution generated byabandoned mining activities in the area of Butte, Montanahas resulted in the designation of the Silver Bow Creek–ButteArea as the largest Superfund (National Priorities List) sitein the U.S. This paper reports the results of bench-scalestudies conducted to develop a resource recovery basedremediation process for the clean up of the Berkeley Pit.The process utilizes selective, sequential precipitation (SSP)of metals as hydroxides and sulfides, such as copper, zinc,aluminum, iron and manganese, from the Berkeley Pit AMDfor their removal from the water in a form suitable foradditional processing into marketable precipitates and pigments.The metal biorecovery and recycle process is based on completeseparation of the biological sulfate reduction step and themetal precipitation step. Hydrogen sulfide produced in the SRBbioreactor systems is used in the precipitation step to forminsoluble metal sulfides. The average metal recoveries usingthe SSP process were as follows: aluminum (as hydroxide) 99.8%,cadmium (as sulfide) 99.7%, cobalt (as sulfide) 99.1% copper(as sulfide) 99.8%, ferrous iron (sulfide) 97.1%, manganese(as sulfide) 87.4%, nickel (as sulfide) 47.8%, and zinc (as sulfide)100%. The average precipitate purity for metals, copper sulfide,ferric hydroxide, zinc sulfide, aluminum hydroxide and manganesesulfide were: 92.4, 81.5, 97.8, 95.6 , 92.1 and 75.0%, respectively.The final produced water contained only calcium and magnesiumand both sulfate and sulfide concentrations were below usablewater limits. Water quality of this agriculturally usable watermet the EPAs gold standard criterion.

STUDIES ON BIOSORPTION OF ZINC(II) AND COPPER(II) ON DESULFOVIBRIO DESULFURICANS

Abstract The objectives of these studies are to determine the equilibrium concentration and kinetics of metal sorption on sulfate-reducing bacteria (SRB) isolates. Adsorption establishes the net reversible cellular metal uptake and is related to SRB metal toxicity and the effects of environmental factors. Results from biosorption equilibria and kinetics of copper(II) and zinc(II) ions on Desulfovibrio desulfuricans and the effects of adsorption of these metals on SRB are discussed. Adsorption studies were conducted using stationary phase cells with equilibrium uptake at 24 h and pHs in the range of 4–7. Equilibrium adsorption in milligram of metal/g dry cell for copper(II) of 2.03 (pH 4.0) and 16.7 (pH 5.0) and zinc(II) of 6.40 (pH 5.5), 13.8 (pH 6.0), 39.2 (pH 6.2) and 49.6 (pH 6.6) was measured experimentally. Negligible biosorption of copper and zinc was found below pH 4.0, with metal sorption increasing within a limited range of pH mainly due to the neutral and/or deprotonated state of binding ligands on cell walls. Competition of metal ions during biosorption was investigated by conducting sorption experiments with Zn(II) using potassium phosphate buffer (KP) and deionized/distilled water. Zn(II) sorption capacity was lower in KP buffer than deionized water due to competition from potassium ions. Scanning Electron Microscope micrographs indicated that metal biosorption on SRB may be related to the production of extracellular polymeric substance (e.g., polysaccharide).

Treatment of acid mine drainage: I. Equilibrium biosorption of zinc and copper on non-viable activated sludge

Biosorption is potentially attractive technology for treatment of acid mine drainage for separation/recovery of metal ions and mitigation of their toxicity to sulfate reducing bacteria. This study describes the equilibrium biosorption of Zn(II) and Cu(II) by nonviable activated sludge in a packed column adsorber. The Zn(II) uptake capacity of unconditioned sludge (not subjected to processing other than drying) was found to decrease in repeated adsorption–desorption cycles, declining by a factor greater than 20 from cycle 1 to cycle 6. Equilibrium uptake of metals by dried sludge conditioned by exposure to deionized water at a pH corresponding to that of the feed solution showed a strong pH dependence and was modeled using the Langmuir adsorption isotherm. Equilibrium metal uptakes from solutions containing single metal ion were 2.5 mg g(dry biomass)−1 and 3.4 mg g(dry biomass)−1 for Zn(II), and 1.9 mg g(dry biomass)−1 and 5.9 mg g(dry biomass)−1 for Cu(II) at pH 3.0 and 3.8, respectively. Equilibrium uptakes from binary mixtures were 30% lower than single component solution uptakes for both metals, indicating some competition between the two metals. No hysteresis was detected between adsorption and desorption equilibria. Anion concentration and pH measurements indicated that simultaneous sorption of metal cation and sulfate anion was probably occurring at pH 3.0, while proton exchange predominated at pH 3.8. Results of the study point to the usefulness of non-viable activated sludge as a biosorbent for recovery/separation of metal ions from acid mine drainages.

Biodegradation kinetics of substituted phenolics: demonstration of a protocol based on electrolytic respirometry

Abstract Data from electrolytic respirometers were used to evaluate the kinetics of biodegradation of phenol, 4-chlorophenol, m -cresol, 2,4-dimethylphenol and 2,4-dinitrophenol through use of spreadsheets and nonlinear curve-fitting. The protocol is explained in detail. 4-Chlorophenol exhibited substrate inhibition kinetics and 2,4-dinitrophenol exhibited product inhibition kinetics. The others could be characterized by Monod kinetics. Values of the kinetic parameters describing biodegradation of each compound are presented.

Advances in biotreatment of acid mine drainage and biorecovery of metals: 2. Membrane bioreactor system for sulfate reduction.

Several biotreatmemt techniques for sulfate conversion by the sulfate reducing bacteria (SRB) have been proposed in the past, however few of them have been practically applied to treat sulfate containing acid mine drainage (AMD). This research deals with development of an innovative polypropylene hollow fiber membrane bioreactor system for the treatment of acid mine water from the Berkeley Pit, Butte, MT, using hydrogen consuming SRB biofilms. The advantages of using the membrane bioreactor over the conventional tall liquid phase sparged gas bioreactor systems are: large microporous membrane surface to the liquid phase; formation of hydrogen sulfide outside the membrane, preventing the mixing with the pressurized hydrogen gas inside the membrane; no requirement of gas recycle compressor; membrane surface is suitable for immobilization of active SRB, resulting in the formation of biofilms, thus preventing washout problems associated with suspended culture reactors; and lower operating costs in membrane bioreactors, eliminating gas recompression and gas recycle costs. Information is provided on sulfate reduction rate studies and on biokinetic tests with suspended SRB in anaerobic digester sludge and sediment master culture reactors and with SRB biofilms in bench-scale SRB membrane bioreactors. Biokinetic parameters have been determined using biokinetic models for the master culture and membrane bioreactor systems. Data are presented on the effect of acid mine water sulfate loading at 25, 50, 75 and 100 ml/min in scale-up SRB membrane units, under varied temperatures (25, 35 and 40 °C) to determine and optimize sulfate conversions for an effective AMD biotreatment. Pilot-scale studies have generated data on the effect of flow rates of acid mine water (MGD) and varied inlet sulfate concentrations in the influents on the resultant outlet sulfate concentration in the effluents and on the number of SRB membrane modules needed for the desired sulfate conversion in those systems. The pilot-scale data indicate that the SRB membrane bioreactors systems can be applied toward field-scale biotreatment of AMD and for recovery of high purity metals and an agriculturally usable water.

Impact of chloroanilines on hydrogenotrophic methanogenesis in ethanol-enriched cultures

The impact of toxic organic chemicals on the kinetics of hydrogen conversion in ethanol-enriched cultures has been investigated. The study first involved an assessment of the kinetics of gaseous hydrogen transformation in a hydrogen-enriched culture. Tests to quantify the distribution of biomass in an ethanol-enriched culture indicated that hydrogenotropic methanogens made up 25.4% of the total biomass. Various amounts of chlorinated anilines were then added to ethanol-enriched test cultures to determine their impact on the hydrogen conversion reaction. Test results indicated that hydrogen conversion was mass-transfer limited from the gas phase but not from solution. While chlorinated anilines had a major adverse impact on acetogenic conversion of ethanol to hydrogen, the associated hydrogenotrophic methanogenesis reaction was affected to lesser extent by the toxicants. Tests with 3-chlorophenol showed similar inhibition of acetogenesis and acetoclastic methanogenesis but not hydrogenotrophic methanogenesis. The principal significance in this study is thought to lie in the use of specific hydrogenotrophic biomass for assessing the kinetics of hydrogen conversion and in the observation that the kinetics of hydrogenotrophic methanogenesis was not adversely affected by chlorinated anilines and chlorinated phenols. The principal application lies in the observation that gas-phase hydrogen may not be a good measure of the impact of toxic organic chemicals on anaerobic digestion processes.

Enhancement of Biodegradation of Alaskan Weathered Crude Oil Components by Indigenous Microbiota with the use of Fertilizers and Nutrients

ABSTRACT Bench-scale biodegradability studies of the Alaskan weathered crude oil were undertaken as part of the bioremediation project for the shorelines of Prince William Sound Alaska, contaminated by the Exxon Valdez oil spill. The purpose of the studies was to evaluate the ability of the indigenous microbial consortium of the seawater and island beach areas to biodegrade the weathered crude oils alkane hydrocarbon and polynuclear aromatic (PAH) constituents in batch-type respirometric reactors and shaker flask systems. Biodegradation studies used Inipol EAP22 and water-soluble nitrogen and phosphorus-containing solution (OECD) as the fertilizer nutrient source. In the respirometric studies, the unpolluted beach material in seawater was spiked with 1,000, 300, and 100 mg/L of weathered crude oil and with Inipol at 5 percent of oil weight or with OECD stock solution concentrates. The contents were brought up to 1,000 mL with seawter. Unpolluted beach material spiked with 10,000, 3,000, and 1,000 mg/L of...

Bioavailability and Biodegradation Kinetics Protocol for Organic Pollutant Compounds to Achieve Environmentally Acceptable Endpoints during Bioremediation

This paper is an extension of our previous studies on quantitating biodegradation kinetics in soil slurry and compacted soil systems. Previous studies had mainly used phenol as a test contaminant. Phenol represents hydrophilic compounds which exhibit high water solubility and low soil sorption characteristics. This paper extends the experimental protocol using polycyclic aromatic hydrocarbons (PAHs) as the test contaminants. PAHs are hydrophobic compounds with low water solubility and exhibit significant partitioning in soil organic carbon. Degradation rates of PAHs are much slower, thereby requiring acclimation of indigenous soil microbiota using microcosm reactors. The experimental protocol, elaborated in this paper, results in the measurement of biokinetic parameters which can be used to quantitate both ex situ and in situ bioremediation rates and assess the attainable endpoints. Biodegradation studies were conducted for naphthalene using soil slurry, soil wafer, and soil column reactors. Microcosm reactors were set-up to acclimate soil microbiota, and carbon dioxide evolution was used as a measure of acclimation. It was found that reasonable degree of PAH acclimation was achieved after 250 days of microcosm operation. Abiotic adsorption/desorption studies showed that equilibrium was achieved in about 20 hours and approximately 45% of the initial amount of naphthalene is adsorbed by the time equilibrium is attained. Further, desorption was much slower than adsorption with equilibrium being attained in 40 hours. Biokinetic parameters were derived from the cumulative oxygen uptake data of soil slurry, wafer, and column reactors using detailed mathematical models. The cumulative oxygen uptake in all three reactors were almost the same, since naphthalene primarily degraded in the soil phase and the extent of degradation in the aqueous phase was small.

Development of Bioavailability and Biokinetics Determination Methods for Organic Pollutants in Soil to Enhance In‐Situ and On‐Site Bioremediation

Determination of biodegradation rates of organics in soil slurry and compacted soil systems is essential for evaluating the efficacy of bioremediation for treatment of contaminated soils. In this paper, a systematic protocol has been developed for evaluating biokinetic and transport parameters in soil slurry and compacted soil bioreactors. The protocol involves abiotic evaluation of adsorption/desorption rates, and equilibria followed by the use of respirometry to determine biodegradation rates using soil slurry, wafer, and porous tube reactors. In the soil slurry reactor, mimicking ex‐situ soil biotreatment, degradation occurs in the aqueous phase by suspended microorganisms and by immobilized microbiota present in the soil phase. In a soil wafer reactor, which consists of a thin layer of soil, biodegradation occurs primarily in the soil phase, as compared to the aqueous phase, which consists of free and bound water in and around the soil particles. The wafer reactor represents biotreatment using bioventing or land farming methods. In the porous tube reactor, rate of oxygen diffusion through the compacted soil affects the overall rate of biodegradation. The porous tube reactor represents in‐situ biotreatment. Experiments were conducted to determine the cumulative oxygen uptake using an uncontaminated low organic carbon soil with phenol as the spiked contaminant. Detailed mathematical models were developed for each type of soil reactor (slurry, wafer, and porous tube), and these models were fitted to the cumulative oxygen uptake data to derive the best‐fit transport and biokinetic parameters. Application of the transport and biokinetic parameters to determine the attainable treatment end points is discussed in this paper.

BIORECOVERY OF METALS FROM ACID MINE DRAINAGE

This paper evaluates an efficient and economic method to selectively recover the dissolved metals present in acid mine drainage systems using sulfate reducing bacteria. In the present study, unlike the conventional treatment, the chemical precipitation of metal sulfates is separated from the biological component of the process. Experiments were performed to obtain optimum pH for selective metal precipitation. These results are compared with the predicted values generated from a thermodynamic equilibrium program. The kinetic parameters for growth of sulfate reducing bacteria at different temperatures and pH are also reported.