Baffled primary facultative ponds with inlets and outlets set at different levels treating domestic wastewater in northeast Brazil.

This study evaluates the performance of four 2.3 m deep pilot-scale, independently loaded, primary facultative ponds treating predominantly domestic sewage in northeast Brazil. The ponds contained longitudinal baffles giving different length to width ratios from 3.55 to 32.4. The ponds had mean hydraulic retention times of ~15 days, and mean surface organic loadings of 330 kg BOD(5).ha.d(-1) during the first experimental phase and 375 kg BOD(5).ha.d(-1) in the second. The vertical inlets and outlets pipes were positioned at 1.8 m and 5 cm respectively below the pond surface in the first phase and at 50 cm and 1.8 m respectively in the second. All the ponds functioned as efficient primary facultative ponds but statistical analysis demonstrated no differences in effluent quality for most of the parameters measured for the various configurations of baffles and inlet and outlet depths. All behaved similarly to the unbaffled pond. The only exceptions were suspended solids and chlorophyll a concentrations which tended to be lower for all combinations of baffles with the outlets set 1.8 m below the surface. This study suggested that the longitudinal baffling of primary facultative ponds when using vertical inlets and outlets may well not significantly improve pond performance.

The removal of ammonia from sanitary landfill leachate using a series of shallow waste stabilization ponds.

This study evaluated the efficiency of a shallow (0.5 m deep) waste stabilization pond series to remove high concentrations of ammonia from sanitary landfill leachate. The pond system was located at EXTRABES, Campina Grande, Paraiba, Northeast Brazil. The pond series was fed with sanitary landfill leachate transported by road tanker to the experimental site from the sanitary landfill of the City of Joao Pessoa, Paraiba. The ammoniacal-N surface loading on the first pond of the series was equivalent to 364 kg ha(-1) d(-1) and the COD surface loading equivalent to 3,690 kg ha(-1) d(-1). The maximum mean ammonia removal efficiency was 99.5% achieved by the third pond in the series which had an effluent concentration of 5.3 mg L(-1) ammoniacal-N for an accumulative HRT of 39.5 days. The removal process was mainly attributed to ammonia volatilization (stripping) from the pond surfaces as a result of high surface pH values and water temperatures of 22-26°C. Shallow pond systems would appear to be a promising technology for stripping ammonia from landfill leachate under tropical conditions.

[Estimates of fertility in Brazil obtained using Arriaga's method]. / Estimativa da fecundidade para o Brasil obtida atraves da tecnica de Arriga.

PIP: In Brazil, as in the majority of developing countries, information from vital statistics is incomplete. This requires the use of indirect estimation techniques to estimate fertility rates. The methods of Mortara, Brass, and Arretx have already been applied to Brazilian data. Eduardo Arriaga, a demographer with the US Census Bureau, has proposed an alternative technique for estimating fertility when information exists from 2 consecutive surveys about live-born children, classified according to the mother's age. To the contrary of the Brass technique, which assumes constant fertility, the hypothesis implicit in Arriaga's method is that the average number of children born per woman varies linearly in the time interval under consideration. In the Brazilian case, where evidence indicates that fertility is declining, Arriaga's technique should be able to determine the validity of this tendency. The procedure used follows the following steps: 1) Obtain the average number of children per woman by individual ages in the survey data, which is divided into 5-year groups. This is followed by a process of intercollation. 2) Estimate the average number of children per woman by individual ages for a year before the 1st survey and a year after the last through linear interpolation. If information is available for more than 2 surveys, an estimate is made for the year preceding and following the data in the intermediate surveys. 3) Specific fertility rates are calculated based on the increase in the average number of children for each cohort. In the case of intermediate surveys, the average between the values of of the preceding and following years are taken. Arriaga's method is applied to Brazilian information, and the results are presented in a series of graphs and tables. Total fertility rate estimates for Brazil from 1941 to 1980 are presented, falling from 5.86 in 1941, to 5.67 in 1972, to 3.82 in 1980. Arriaga's technique also permits calculation of the average number of children for each cohort, making it possible to verify the compatability of information about parturition coming from various sources. Several instances of incompatability of data, particularly in the older cohorts, appears. It is recommended that other methods of determining actual fertility be applied to Brazilian data, to establish the level and trend of Brazilian fertility with a certain level of assurance.^ieng