Elimination of total coliforms and Escherichia coli from water by means of filtration with natural clays and silica sand in developing countries.

This research presents the results of a pilot system used for water treatment to be supplied to single-family or small housing nucleus at rural sector. The pilot system is constituted by an up-flow aerated filter with ceramic carrier, followed by a second down-flow filter of silica sand. The pilot plant was installed in a rural sector of the province of Loja, Ecuador, with the main purpose of monitoring the reduction in bacteria in the water for human consumption. Two natural clays from the area were tested. They were transformed into sphere-type ceramics, and then, they were placed in the pilot filters. These both natural clays are inorganic materials with high content of aluminosilicate clay minerals with favourable characteristics to achieve greater efficiency for the reduction in bacteria. The acclimatization time of 60 days allowed to achieve optimum treatment efficiency performance until 90 days of operation. The physicochemical parameters, namely temperature, pH, dissolved oxygen and total dissolved solids, were monitored throughout the experiments. Regarding microbiological parameters, up to 99% of total coliforms removal was reached for the clay called CF-CC and 79% for the other, called CF-CV. In addition, 100% of total coliforms and Escherichia Coli removal was reached for both clay systems. Social and economic viability of the proposed treatment is also analysed in the manuscript.

Nitrogen removal capacity and bacterial community dynamics of a Canon biofilter system at different organic matter concentrations.

Three Canon bench-scale bioreactors with a volume of 2 L operating in parallel were configured as submerged biofilters. In the present study we investigated the effects of a high ammonium concentration (320 mgNH4+· L-1) and different concentrations of organic matter (0, 100 and 400 mgCOD·L-1) on the nitrogen removal capacity and the bacterial community structure. After 60 days, the Canon biofilters operated properly under concentrations of 0 and 100 mgCOD·L-1 of organic matter, with nitrogen removal efficiencies up to 85%. However, a higher concentration of organic matter (400 mgCOD·L-1) produced a partial inhibition of nitrogen removal (68.1% efficiency). The addition of higher concentrations of organic matter a modified the bacterial community structure in the Canon biofilter, increasing the proliferation of heterotrophic bacteria related to the genera of Thauera, Longilinea, Ornatilinea, Thermomarinilinea, unclassified Chlorobiales and Denitratisoma. However, heterotrophic bacteria co-exist with Nitrosomonas and Candidatus Scalindua. Thus, our study confirms the co-existence of different microbial activities (AOB, Anammox and denitrification) and the adaptation of a fixed-biofilm system to different concentrations of organic matter.

[The role of thiazides in the prophylaxis of recurrent calcium lithiasis]. / Papel de las tiazidas en la profilaxis de la litiasis cálcica recidivante.

OBJECTIVE: To show the prolonged efficacy of thiazides in the prophylaxis and treatment of recurrences in patients with calcium oxalate and phosphate lithiasis. METHODS: A randomised prospective study is conducted, with a three-year follow-up, in 150 patients diagnosed with recurrent calcium lithiasis. The patients are divided into three groups: A) 50 cases subject to observation with no treatment, B) 50 cases treated with 50 mg/day of hydrochlorothiazide, and C) 50 cases treated with 50 mg of hydrochlorothiazide and 20 mlEq of potassium citrate/day. Each group is subject to a renal study with imaging techniques and a urinary metabolic study at baseline, 12, 24 and 36 months. RESULTS: The patients treated with thiazides (Groups B and C) obtain a significant reduction in lithiasis recurrence compared with the control group (Group A). The most common abnormality found in the metabolic study was hypercalciuria, 52% of cases; 16% present a mixed lithogenic pattern. The number of recurrences and need for new sessions of extracorporeal lithotripsy in patients with hypercalciuria treated with thiazides is significantly smaller than in Group A (p=0.003). CONCLUSIONS: We observe a significant relation between lithogenic pattern and lithiasis recurrence. Thiazides help us to control lithogenic factors and recurrences in patients with calcium lithiasis. This effect is prolonged and significant in patients with hypercalciuria.