Removal of groundwater arsenic using a household filter with iron spikes and stainless steel

Arsenic (As) in groundwater for domestic use poses a worldwide threat to public health, most notably in rural areas. The aims of this study were: first, determine groundwater composition in a mining area in central Mexico (Huautla); second, assess As exposure through human groundwater consumption and; third, develop and test a household filter to obtain drinking water for these rural communities. From the 17th century through the 1990s, mines in the area produced Ag-galena and sphalerite from volcanic rock. Groundwater flooded the mines when they were abandoned due to low silver prices. Local households now use the water to meet domestic needs. Water from the mines was found to have high As content (0.04-0.26 mg L(-1)) and Fe, Mn, Pb and Cd were also above Mexican drinking water standards and WHO guidelines. All the population in the Huautla community was exposed to the metalloid through water used in food preparation. The best As removal was obtained with a filter using oxidized commercial fiber (HCl 2N as oxidant). Concentrations in the effluent were below Mexican drinking water standards (0.025 mg As L(-1) water) during the 105-day (2520 h) filter operation, with a maximum As removal efficiency of 95.4%. The household filter was simple, low-cost and may be very attractive for As removal in rural areas in developing countries.

Effect of aerobic pretreatment with Aspergillus terreus on the anaerobic digestion of olive-mill wastewater

A kinetic study was carried out on the anaerobic digestion of olive-mill wastewater (OMW) and OMW that was previously fermented with Aspergillus terreus. The bioreactors used were batch fed and contained saponite as support for the mediating bacteria. The anaerobic digestion process followed first-order kinetics, from which the kinetic constant A was calculated using a non-linear regression. This kinetic parameter was influenced by the pretreatment carried out, and was 3.7 times higher for pretreated OMW than for untreated OMW. The anaerobic processing of pretreated OMW seemingly involved no inhibition phenomena as the biotoxicity and the total phenolic compound content (analysed by HPLC) were reduced by 71.2% and 77.9% respectively as a result of the pretreatment. Finally, the yield coefficient of methane production was 0.345 litres of methane (at standard temperature and pressure)/g of chemical oxygen demand, that is, 23% higher than that provided by untreated wastewater.