MICROBIAL REMOVAL OF SILVER AND GOLD FROM LOW-GRADE INDUSTRIAL WASTEWATERS

METALS ARE AMONG THE MOST WIDELY USED RAW MATERIALS IN TODAY'S INDUSTRIAL SOCIETY. CONSEQUENTLY WASTEWATERS FROM METAL-PRODUCING AND METAL-CONSUMING INDUSTRIES CONTAIN HIGH CONCENTRATIONS OF METALS. IN ADDITION TO THE WATER CONTAMINATION PROBLEM, THE METALS LOST ARE EXTEMELY VALUABLE. ANNUAL LOSSES OF PRECIOUS METALS FROM JUST ONE SEGMENT OF THE INDUSTRY - JEWELRY MANUFACTURING - ARE ESTIMATED AT 840 KG SILVER AND 1643 KG GOLD; THE LATTER IS VALUED AT $23.4 MILLION. THE OBJECTIVE OF THE PROPOSED RESEARCH IS TO ASSESS THE FEASIBILITY OF USING NON-GROWING MICROORGANISMS AS BIOSORPTION AGENTS FOR LOW-COST, ENERGY EFFICIENT AND EFFECTIVE REMOVAL OF SILVER AND GOLD FROM LOW GRADE, HIGH-VOLUME INDUSTRIAL WASTEWATERS. ELEMENTS OF THE RESEARCH PLAN INCLUDE: DETERMINING WHAT NON-GROWING MICROORGANISMS MOST EFFECTIVELY REMOVE PRECIOUS METALS FROM SOLUTION; THE KINETICS OF METAL BIOSORPTION; OPTIMUM CONDITIONS FOR BIOSORPTION; METAL UPTAKE CAPACITY BY THE ORGANISMS; AND QUANTITATIVE ASSESSMENT OF SCHEMES FOR IMMOBILIZATION OF THE MICROBIAL AGENTS. IN THE RESEARCH PLAN SPECIAL EMPHASIS IS PLACED ON UNDERSTANDING THE MICROBIAL/METAL INTERACTIONS SINCE INDUSTRIAL EFFLUENTS CONTAIN A VARIETY OF ORGANIC AND INORGANIC ADDITIVES AND COMPLEXING AGENTS THAT COMPLICATE THE AQUEOUS CHEMISTRY OF THE SYSTEMS. THE PROPOSED RESEARCH IS EXPECTED TO GREATLY EXPAND THE CONCEPT OF USING IMMOBILIZED MICROORGANISMS FOR TREATMENT OF METALLIFEROUS WASTEWATERS. THE QUANTITATIVE DATA GAINED THROUGH THE BENCH-SCALE STUDIES WILL ASSESS THE POTENTIAL UTILITY OF THIS EMERGING TECHNOLOGY AND WILL BE USED FOR DESIGN AND CONSTRUCTION OF SCALE-UP UNITS FOR DETERMINING COMMERCIAL FEASIBILITY.