International audience | Biofilm development in wastewater treatment system by soil infiltration is often mentioned for its participation to purification efficiency and clogging zone formation. It appears necessary to understand its evolution in order to better control the operation of these systems. The objective of this study was to improve knowledge about the temporal evolution of the biofilm structure in the first centimetres of infiltration system. For this purpose, metabolic fingerprints by Biolog EcoPlate (TM) and molecular fingerprints by Ribosomal Intergenic Spacer Analysis (RISA) were carried out on sand, septic effluent and treated effluent samples from two experimental reactors supplied with different hydraulic loads collected at different times. The metabolic capabilities of sand microflora decreased in time. In the same way, molecular structure of the biofilm community changed and converged to similar structure in time. Principal components analysis on RISA gel revealed a ''buffering effect'' of the sand filter on the genetic structure of the bacterial community from treated effluent. The kinetics of evolution of the both metabolic and genetic fingerprints showed a reduction of the metabolic and genetic potentials of septic and treated effluents for the same times. The population dynamic within the biofilms appears interesting evidence in the comprehension of the operation of the treatment systems.

International audience | Biofilm development in wastewater treatment system by soil infiltration is often mentioned for its participation to purification efficiency and clogging zone formation. It appears necessary to understand its evolution in order to better control the operation of these systems. The objective of this study was to improve knowledge about the temporal evolution of the biofilm structure in the first centimetres of infiltration system. For this purpose, metabolic fingerprints by Biolog EcoPlate (TM) and molecular fingerprints by Ribosomal Intergenic Spacer Analysis (RISA) were carried out on sand, septic effluent and treated effluent samples from two experimental reactors supplied with different hydraulic loads collected at different times. The metabolic capabilities of sand microflora decreased in time. In the same way, molecular structure of the biofilm community changed and converged to similar structure in time. Principal components analysis on RISA gel revealed a ''buffering effect'' of the sand filter on the genetic structure of the bacterial community from treated effluent. The kinetics of evolution of the both metabolic and genetic fingerprints showed a reduction of the metabolic and genetic potentials of septic and treated effluents for the same times. The population dynamic within the biofilms appears interesting evidence in the comprehension of the operation of the treatment systems.

Biofilm development in wastewater treatment system by soil infiltration is often mentioned for its participation to purification efficiency and clogging zone formation. It appears necessary to understand its evolution in order to better control the operation of these systems. The objective of this study was to improve knowledge about the temporal evolution of the biofilm structure in the first centimetres of infiltration system. For this purpose, metabolic fingerprints by Biolog EcoPlate[trade mark sign] and molecular fingerprints by Ribosomal Intergenic Spacer Analysis (RISA) were carried out on sand, septic effluent and treated effluent samples from two experimental reactors supplied with different hydraulic loads collected at different times. The metabolic capabilities of sand microflora decreased in time. In the same way, molecular structure of the biofilm community changed and converged to similar structure in time. Principal components analysis on RISA gel revealed a “buffering effect” of the sand filter on the genetic structure of the bacterial community from treated effluent. The kinetics of evolution of the both metabolic and genetic fingerprints showed a reduction of the metabolic and genetic potentials of septic and treated effluents for the same times. The population dynamic within the biofilms appears interesting evidence in the comprehension of the operation of the treatment systems.

A biological source treatment (BST) technique using remote sensing and biogeochemistry has been developed to address acid mine drainage (AMD) at its source. The BST technique utilizes down-hole injections of microbial inoculum and substrate amendments to establish a biofilm on the surface of metal sulfides (AMD source material). The treatment results in an elevated groundwater pH (from acidic to circum-neutral levels) and prevents further oxidation of AMD source material. The first 2 years of an ongoing field study of the BST technique at a reclaimed coal mine in central Tennessee (USA) has produced successful results. For instance, the water chemistry in a monitoring well down-gradient from injection wells has improved substantially as follows: the pH increased 1.3 units from 5.7 to 7.3, the dissolved (0.45 μm-filtered) iron concentration decreased by 84% from 93 to 15 mg/l, the conductivity decreased by 379 μS/cm, and sulfate decreased by 78 mg/l. Electromagnetic induction surveys were conducted to identify AMD source material and monitor BST performance by measuring changes in subsurface resistivity throughout the site. These surveys revealed a treatment zone created between injection wells where the resistance of contaminated groundwater from up-gradient AMD sources increased as it flowed past injection wells, thus, suggesting this technique could be used to treat AMD sources directly or to intercept and neutralize sub-surface AMD.