Abstract: The 1,3-benzenediamidoethanethiol dianion (BDET, known commercially as MetX) has been developed to selectively and irreversibly bind soft heavy metals from aqueous solution. In the present study BDET was found to remove >90% of several toxic or problematic metals from AMD samples taken from an abandoned mine in Pikeville, Kentucky. The concentrations of metals such as iron, may be reduced at pH 4.5 from 194 ppm to below 0.009 ppm. The formation of stoichiomietric BDET-metal precipitates in this process was confirmed using X-ray powder diffraction (XRD), proton nuclear magnetic resonance (1H NMR), and infrared spectroscopy (IR).

Abstract: Sulfate reducing passive bioreactors are increasingly being used to remove metals and raise the pH of acidic waste streams from abandoned mines. These systems commonly use a variety of organic substrates (i.e. manure, wood chips) for sulfate reduction. The effectiveness of these systems decreases as easily accessible reducing equivalents are consumed in the substrate through microbial activity. Using column studies at room temperature (23-26 degrees C), we investigated the addition of lactate and methanol to a depleted manure substrate as a method to reactivate a bioreactor that had lost >95% of sulfate reduction activity. A preliminary experiment compared sulfate removal in gravity fed, flow through bioreactors in which similar masses of each substrate were added to the influent solution. Addition of 148 mg/l lactate resulted in a 69% reduction in sulfate concentration from 300 to 92 mg/l, while addition of 144 mg/l methanol resulted in an 88% reduction in sulfate concentration from 300 to 36 mg/l. Because methanol was found to be an effective sulfate reducing substrate, it was chosen for further experiments due to its inherent physical properties (cost, low freezing point and low viscosity liquid) that make it a superior substrate for remote, high elevation sites where freezing temperatures would hamper the use of aqueous solutions. In these column studies, water containing sulfate and ferrous iron was gravity-fed through the bioreactor columns, along with predetermined methanol concentrations containing reducing equivalents to remove 54% of the sulfate. Following an acclimation period for the columns, sulfate concentrations were reduced from of 900 mg/l in the influent to 454 mg/l in the effluent, that reflects a 93% efficiency of electrons from the donor to the terminal electron acceptor. Iron concentrations were reduced from 100 to 2 mg/l and the pH increased nearly 2 units. (C) 1999 Elsevier Science Ltd.

Abstract: The drainage water from mines in Poland has a daily contribution of, in the order of magnitude, 6,500 tons of chlorides and 0.5 ton of sulphates to the rivers Vistula (Wisla) and Oder (Odra). The largest amounts of these salts, about 78%, derive from 18 mines located mainly in the Katowice mine district. The high salt content in the water from the Vistula prevents at present its use in agriculture and causes tremendous economic losses due to corrosion attacks on pipes, machines, etc., within the industry. At present only about 4% of the river water can be classified as drinking water. To combat this problem a desalination project in Katowice has now almost been completed, including advanced treatment of wastewater for zero discharge from the two adjacent coal mines, Debiensko and Budryk. It implies elimination of 310 tons/d of salt discharge to the Odra River. The complete treatment processes are divided into three main sections: (1) pretreatment before reverse osmosis (RO) of about 12,400 m3/d drainage water from the two mines with a salinity of around 16,000 mg/l TDS on the average; (2) RO plant including post-treatment of the RO permeate; (3) a thermal plant for concentration of brine (about 4,600 m3/d) and separation of sodium chloride (NaCl) by crystallization, centrifuging and drying. The RO pretreatment includes algicide dosing in a storage tank, disinfection, flocculation/sedimentation and dual media filtration as well as granular activated carbon filtration. After a two-stage microfilter system (50 μ and 5 μ, respectively), the pretreated water is desalinated at 6-7 MPa in a RO system with spiral wound RO membranes. The RO permeate is decarbonated in a part-flow followed by addition of chemicals for disinfection and increase of the temporary hardness before distribution in the drinking water net. The flow into the thermal plant consists of the RO reject (about 2,700 m3/d) with a salinity of around 80 g/l TDS and the brine flow (about 1,870 m3/d) from the Budryk mine with about the same salinity. The first section of the thermal plant is composed of two brine concentrators, designed by Resources Conservation Company (RCC), USA. By using the seed crystal recycling technique it is possible to concentrate the feed to near the precipitation point for NaCl. The second section of the thermal plant includes one crystallizer for production of NaCl, two pusher centrifuges for salt removal from supersaturated brine and one fluidized bed dryer. The crystallizer is a forced circulation submerged-tube evaporator equipped with a mechanical vapor compressor. An additional section is also planned to be constructed for treatment of the purge from the crystallizer in order to recover other valuable chemical products and distillate. The process is fully automatic and controlled by programmable logic controllers. The plant has finally been designed by Energotechnika, Poland, after preparation of technical and economical planning of the project in coordination with Nordcap Ltd., RCC and VBB Viak-SWECO, Stockholm. In the summer 1994 the thermal plant was started up, and the RO plant is expected to be in operation during the spring 1995. The paper covers the project design with illustrations of the main parts of the plant and summarizes the results of the initial operation.