Two of the main drawbacks to be overcome before full scale implementation of boron-doped diamond electro-oxidation were addressed in this work; its energy consumption and hazard of formation of chlorinated organics. This was framed within a study in which the technical and economic feasibility of BDD electro-oxidation of landfill leachate was evaluated at pilot scale. On one hand, its technical feasibility was assessed based on COD and NH(4)(+) removal, allowing the selection of the operation conditions that provide optimal energy efficiency, and special attention was paid to the risk of formation of undesired by-products such as nitrite, nitrate ions and trihalomethanes. On the other hand, treatment costs were estimated based on energy consumption required to reach the disposal limits to natural watercourses established by legislation. The results were compared with those of other commonly used AOPs. Under the operating conditions studied, the concentration of COD decreased below the disposal limit (160 mg L(-1)) and ammonia concentration reached values as low as 30 mg L(-1). The energy consumption needed was estimated at 54 kWh/m(3) and the formation of chlorination by-products appeared to be low as the maximum total trihalomethane concentration detected was 432 microg/L.

The objective of the present study was to determine recalled age at menarche in women of Quechua and non-Quechua ancestry living in the cities of Lima (altitude 150 m), Cusco (altitude 3,400 m), and Cerro de Pasco (altitude 4,340 m), Perú. The sample included 296 Mestizo urban women, 20-30 years, who were natives of Lima (n = 72), Cusco (n = 81), and Cerro de Pasco (n = 143). Ethnic composition was determined by two parental surnames, and women were classified as Quechua when one or both surnames were of Quechua origin and non-Quechua when both surnames were of Spanish origin. Age at menarche was obtained by recall to nearest year. In Quechua as in non-Quechua women, age at menarche occurred later as residence altitude increased. Mean ages at menarche for the combined Quechua and non-Quechua samples were 13.1 ± 1.4 years in Lima, 13.9 ± 1.9 years in Cusco, and 14.6 ± 1.69 years in Cerro de Pasco. Thus age at menarche occurs later at high altitude independent of ethnic influence. © 1994 Wiley-Liss, Inc.

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Tilapia are among the most widely cultivated fish species in the world, with a high level of importance for freshwater fish production. An important tilapia variety for the international market is genetically improved farmed tilapia (GIFT; Nile Tilapia Oreochromis niloticus). Multiple studies have been developed to determine the maximum concentrations of ammonia (NH 3 ) recommended for the cultivation of various varieties of tilapia; however, there are no specific data for the cultivation of GIFT. Growth results for GIFT fry exposed to NH 3 at 0.50, 0.89, and 1.58 mg/L in 69-d chronic toxicity tests were evaluated. The experiments were conducted in three recirculation aquaculture systems, one for each concentration of NH 3 . Stocking densities were 33, 66, and 132 fish/m 3 . Fish were fed ad libitum three times per day. The only mortalities recorded were for treatments with the highest NH 3 concentration (1.58 mg/ L), which had a cumulative mortality of 89.5%. There were no significant differences in weight gain for the three stocking densities assessed at an NH 3 concentration of 0.50 mg/L. Results indicated that GIFT juveniles can be cultured with stocking densities of up to 132 fish/m 3 in environments with ammonia concentrations of up to 0.89 mg/L without compromising fish survival, although the daily weight gain was between 30% and 41% lower than the values reported for optimal culture conditions.

The core objective of the study was to evaluate the organic matter and nitrogen removal efficiency in a recirculating aquaculture system for the intensive laboratory-bred rainbow trout. The treatment system consisted of an upflow reactor which operated at a hydraulic retention time (HRT) of 18 and 36 min, a pre-filtration unit with HRT of 4.9 and 9.8 min, a three-phase airlift fluidized bed reactor operated at HRT between 5 and 11 min, a granular unit for the upflow and the fluidized bed reactors effluents filtration with 5.8 and 11.6 min as HRT, and an ultraviolet (UV) unit for the final effluent disinfection. A plastic material was used as support media in the upflow reactor, and granular zeolite with an effective size of 1.30 mm in an 80 g/L constant concentration was used as a carrier for the fluidized bed reactor. Average removal efficiencies of biochemical oxygen demand (BOD) chemical oxygen demand (COD), ammonium, nitrite, nitrate, and total nitrogen were 94.4, 91.7, 52.5, 13.4, 1.3 and 6.0% respectively. In the rainbow trout rearing tanks, there was a water volume of 125 L and water exchange rates of 125 and 250 L/h, there were no registered mortalities; the calculated daily weight gains were 1.55 and 1.51 g/day and the final stocking densities were respectively 20.87 and 20.58 kg/m3. The results suggested that the system had the capability to develop a nitrification process for maintaining water quality characteristics within the recommended values for rainbow trout farming, but total nitrogen was not effectively removed due to the weak denitrification process, since there were modest values of nitrite and overall nitrogen removal.

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