Mateus Pimentel de Matos

Coliform bacteria removal from sewage in constructed wetlands planted with Mentha aquatica

The present study evaluated the performance of the species Mentha aquatica in constructed wetlands of horizontal subsurface flow (CW-HSSF) with regard to the removal of coliforms bacteria in an effluent from the primary treatment of sewage as well as to obtain adjustment parameters of the bacterial decay kinetic model along the length of the CW-HSSF. Therefore, four CW-HSSFs measuring 24.0 m×1.0 m×0.35 m were built and filled with # 0 gravel as the support medium to a height of 0.20 m. Two of the CW-HSSFs were planted with the species M. aquatica, while the other two remained uncultivated. Cultivation of M. aquatica in CW-HSSF resulted in total coliforms (TC) and Escherichia coli (EC) removals from 0.9 to 1.3 log units greater than those obtained in the uncultivated experimental plots, for the hydraulic retention times (HRTs) of 4.5 and 6.0 days. For HRT ranged from 1.5 to 6.0 days, the highest removal efficiencies in counts of TC and EC were obtained when using longer HRT. The mathematical models evaluated showed good fit to average counts of TC and EC highlighting the modified first-order kinetic model with the inclusion of the power parameter in the HRT variable.

Saturação do complexo de troca de solos oxídicos com sódio

This study investigated the influence of physical, chemical and mineralogical properties of three oxidic soils in their potential sodification. In this evaluation, samples collected in the B horizon of two Oxisol and a Ultisol were used, which presented, respectively, high presence of the mineral kaolinite, hematite and gibbsite. Samples were subjected to physical, chemical and mineralogical analysis and filled soil columns were submitted to leaching with solutions of electrical conductivity (CE) of 8.0 dS m-1 and sodium adsorption ratio (SAR) 0, 10, 20, 30, 40 and 50 (mmol L-1) 0.5, in three replications. The exchangeable sodium percentage (ESP) and exchangeable sodium adsorption ratio (ESR) were obtained by calculation from the values of exchangeable sodium in the soil. The increase in the SAR of percolation solution provided an increase in the ESR and ESP of all soils and was influenced by the mineralogy, weathering degree and clay content of soil. The analysed soils can receive waters with high SAR and EC without suffering significant sodification.

Effect of time-temperature binomial in obtaining biochemical oxygen demand of different wastewaters

Studies on the effects of temperature and time of incubation of wastewater samples for the estimation of biodegradable organic matter through the biochemical oxygen demand (BOD), that nowadays are rare, considering that the results of the classic study of STREETER & PHELPS(1925) have been accepted as standard. However, there are still questions how could be possible to reduce the incubation time; whether the coefficient of temperature (θ) varies with the temperature and with the type of wastewater and if it approaches 1.047. Aiming the elucidation of these questions, wastewater samples of dairy, swine and sewage treated in septic tanks were incubated at temperatures of 20, 30 and 35 °C, respectively for 5, 3.16 and 2.5 days. From the parameter of deoxygenation coefficient at 20 °C (k20), θ30 and θ35 were calculated. The results indicated that θ values changes with the type of wastewater, however does not vary in the temperature range between 30 and 35 °C, and that the use of 1.047 value did not implied significant differences in obtaining k in a determined T temperature. Thus, it is observed that the value of θ can be used to estimate the required incubation time of the samples at different temperatures.

MINERALIZAÇÃO DO CARBONO E NITROGÊNIO DE RESÍDUOS APLICADOS AO SOLO EM CAMPO

The definition of application rates of organic waste from agricultural, urban or industrial sources, with a view to agricultural re-use must be based on the soil mineralization rate. The objective of this study was to test different estimation methods of mineralized fractions of cattle, pig and poultry manure, as well as of sewage sludge and municipal solid waste compost, under field conditions, incorporated or applied to the surface of a Red-Yellow Latosol (LVAd). The experiment was conducted for 360 days and soil/residues were monthly sampled for analysis of readily oxidisable organic carbon (OCro), total N, ammonium and nitrate concentrations, allowing the estimation of organic N (ON). The estimates of mineralized fractions of surface-applied residues were more biased than of incorporated wastes, as shown by different soil/residue proportions collected during the monitoring period. It is recommended to calculate the mineralized fractions using OCro data of the soil/residues, because the inorganic N and therefore ON is strongly influenced by rainfall, resulting in unreliable values. After 120 days of residue incubation, the mineralized fractions of OCro and NO, estimated based on the applied organic material (OCro or ON), were over 89.3 %, for incorporated and surface-applied wastes.