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Sanitary landfill leachate (SLL) is a mixture of highly toxic and recalcitrant pollutants that threatens the water quality of the Yucatán Peninsula karst aquifer, one of the most extensive aquifers on the planet. To reduce the adverse environmental impacts of this wastewater, a triple-stage Fenton process (FP) was applied in an old SLL. Removal efficiencies were evaluated in terms of physicochemical variables, metal(oid)s concentrations, mass spectrometric identification of organic compounds and Daphnia magna acute toxicity test. The triple-stage FP achieved an 88% chemical oxygen demand (COD) removal, representing an improvement of 13% compared to FP performed in a single stage. Further, metal(oid)s such as aluminum, arsenic, chromium, nickel and zinc as well as organic compounds were substantially reduced. With respect to acute toxicity, the treatment produced a 64% reduction. Thus, this treatment system seems to be an effective option to reduce the dangerous level of SLL.

This study evaluates the capability of horizontal subsurface-flow constructed wetlands (SSF CWs) for treating pretreated swine wastewater as a function of contact time (CT) and type of macrophyte under the local conditions of Yucatán, Mexico. Experiments were conducted from July 2004 to November 2005 on a swine-fattening farm. The study had three stages: first, macrophytes were located and collected; second, plants were acclimatised; and third, a pilot plant with 6 wetlands was set up, operated and evaluated. The effectiveness of the wetlands was intensively tested over 2 periods (April and November 2005). The results indicate that treatment efficiency significantly improved with increased CT for most of the analysed contaminants. The highest removal rates were recorded at a CT of 3 d and ranged between 64 and 78% for total suspended solids, 52 and 78% for COD, 57 and 74% for BOD5, 57 and 79% for total nitrogen, 63 and 75% for ammonium nitrogen, 70 and 81% for nitrate, 0 and 28% for total phosphorus and 3.3 and 4.2 log-units for total coliforms. Results also suggest that the macrophyte species used did not significantly differ on their contribution to overall treatment efficiency. However, vegetated beds slightly improved water quality when compared to unplanted systems. Horizontal SSF CWs are a suitable technology for treating swine wastewater under the local conditions of Yucatán. Contact time should be given special attention in the design of future full-scale facilities.