Drinking water production from well water with high sulfur and sulfur bacteria content

Problems with treatment of Ahaste well water (Audru Parish, Parnu County, Estonia) were studied in field conditions. The groundwater contains a significant amount of sulfur, from which at pH=7.5-8.0 about 70-90% is in the form of hydrogen sulfide ion and 30-10% in the form of dissolved H2S. After aeration in the summer, this water formed an unknown slimy microbial mass with a distinct sulfuric odor, which clogged the aeration tanks, catalytic filters, and even the distribution network up to the consumers. After laboratory analyses, it was established that this unknown microbial mass is obviously the filiform sulfur bacteria Thiothrix, together with particles of free sulfur. It was found that this mass formed during enrichment under warm conditions using air as the oxidizer. Under these conditions, elemental sulfur was liberated and created favorable conditions for the Thiothrix to thrive using the elemental sulfur as their food source. A new treatment technology for this well water was developed using ozone as a strong oxidant/disinfectant, followed by filtration through an Everzit-Special, a material, which besides filtration, partially behaves as an adsorbent. The capital and operation costs of the new technology were estimated.