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Water scarcity, the degradation of freshwater resources, and wastewater pollution are reaching crisis levels, especially in arid regions of the world. The reuse of wastewater was investigated by using intermittent media infiltration (IMI) to evaluate fecal coliform (FC) removal efficiency. Twelve IMI columns were packed with soil and natural filtering materials (sand, zeolite, vermicompost and charcoal) at percentages of 25, 50 and 75. The municipal wastewater was treated for the FC analysis for four weeks. The chemistry, physics, and morphology of the filter media as related to FC reduction were determined and characterized. Fine particle size and adsorption capacity are important factors for retaining FCs. The mixture of clay soil and filter media in a ratio of 75/25 gave the best performance for FC removal, and the average FC reductions for sand, zeolite, vermicompost and charcoal were 94.4%, 82.2%, 93.8% and 99.6%, respectively. The IMI of soil/charcoal gave a higher log removal (2.19-2.46 log) than the other media, and the effluent complied with Mexican regulations for unrestricted agricultural irrigation. These results showed good performance for FC removal and strengthened the possibility of using reclaimed municipal wastewater in unrestricted irrigation.

The reclamation of domestic wastewater for irrigation is one alternative approach to solve the water scarcity crisis, but it is essential to control the microbiological quality of wastewater used for irrigation. The removal of thermotolerant coliforms, also known as faecal coliforms (FC), from treated domestic wastewater by intermittent media infiltration (IMI) in column was studied. The columns were filled with natural filter media (soil, soil/charcoal and zinc-modified zeolite, Zeo-Zn), and wastewater, IMI-treated wastewater and disinfected wastewater were compared. The numbers of residual FC on Swiss chard (Beta vulgaris) and in agricultural soil were determined over a 4-month period. The column using Zeo-Zn had a higher FC removal efficiency (2.98 log) than columns with other filter media and disinfection (1.87-2.57 log) due to the bactericidal properties of Zn(2+). The treatment of wastewater using Zeo-Zn and disinfection both decreased the accumulation of FC on plants and in soil to approximately 1-20 MPN/g dry matter. IMI-treated wastewater using the column with Zeo-Zn was suitable for unrestricted agricultural use, complied with Mexican regulations (as did disinfected wastewater) and had a low risk of FC contamination of plants and soil.

In the “Laguna” region of Coahuila state, Mexico like other places in the world, the groundwater needs to be treated to meet the quality required for human consumption. The study had probed that a Mexican fly ash can be used as a raw material to obtain effective low cost adsorbents for drinking water treatment, as well evaluated the effects of pH, ion coexistence, dose, arsenic (As) concentration and temperature on the As(V) uptake by using P and W modified zeolites (PMOD and WMOD) obtained from a Mexican fly ash. The As(V) adsorption capacity of the WMOD zeolite was not affected by pH and As(V) concentrations in aqueous solution was achieved <0.01 mg/L in the studied pH range; however, the As(V) removal by using PMOD zeolite decreased at high pH values. Carbonate concentration had a negative effect on the As(V) uptake of both zeolites but this effect was higher for the PMOD zeolite. The maximum adsorption capacities (Qmax) were 76.11 and 44.44 mg of As(V)/g of zeolite for the WMOD and the PMOD zeolites, respectively. The adsorption process was endothermic, spontaneous and occurred by chemical exchange. The experimental data were best interpreted by a pseudo-second order kinetic model. The WMOD zeolite showed a higher adsorption capacity and rate than the PMOD even at the highest evaluated As(V) concentration. The adsorption capacity of the regenerated WMOD zeolite was similar to the original zeolite. Because of the high As(V) adsorption capacity, chemical stability and regenerability, the WMOD zeolite is potentially useful as low-cost adsorbent for As(V) removal from aqueous effluents.