Data on intensity-duration-frequency or design rainfall are one of the most important information required for various hydrological and water resources studies. However, such crucial data are often unavailable in various parts of the world due to lack of enough rain gauging stations. It is not only tedious to determine design rainfall from the raw data but also occasionally impossible to calculate due to lack or absence of short-duration rainfall data. Generally, the manual rain gauges outnumber the automatic gauges, making it difficult to have adequate data on short-duration rainfall values, which is very important for urban hydrology. However, no graphical or mathematical relation could be found in the literature, which can be used for quick estimation of short-duration design rainfall from the daily rainfall data recorded by the manual stations. Annual maximum rainfall data from 143 rain gauging stations located at Klang Valley in Malaysia were used in this study. Statistical analyses and logarithmic graph fitting techniques were used to develop excellent correlation between short-duration rainfall and daily rainfall values for 96 automatic and 46 manual stations. Rainfall data analyze the design rainfall data of various duration and return periods. The 15, 30 and 45 min of short-duration rainfall, which is the most common rainfall duration in the study area, was observed to be 32.4%, 47.1% and 57.4% of the daily rainfall amount, respectively. The amount of rainfall during 1-, 2-and 3-h storm events contribute 64.9%, 76.5% and 80.9% of the daily rainfall. Such relations can be used for quick estimation of short-duration rainfall resulting in saving time, money and other resources.

This study enhanced the production of thermostable organic solvent-tolerant (TS-OST) lipase by locally isolated thermotolerant sp. strain using solid-state fermentation (SSF) of palm kernel cake (PKC). The optimum conditions were achieved using a series of statistical approaches. The cultivation parameters, which include fermentation time, moisture content, temperature, pH, inoculum size, various carbon and nitrogen sources, as well as other supplements, were initially screened by the definitive screening design, and one-factor-at-a-time using PKC as the basal medium. Three significant factors (olive oil concentration, pH, and inoculum size) were further optimized using face-centred central composite design. The results indicated a successful and significant improvement of lipase activity by almost two-fold compared to the initial screening production. The findings showed that the optimal conditions were 2% (v/w) inoculum size, 2% (v/w) olive oil, 0.6% (w/w) peptone, 2% (v/w) ethanol, 70% moisture content at initial pH 10.0 and 45 °C within 72 h of fermentation. Process optimization resulted in maximum lipase activity of 58.63 U/gram dry solids (gds). The analysis of variance showed that the statistical model was significant ( value <0.0001) and reliable with a high value of (0.98) and adjusted (0.96). This indicates a better correlation between the actual and predicted responses of lipase production. By considering this study, the low-cost PKC through SSF appears to be promising in the utilization of agro-industrial waste for TS-OST lipase production. This is because satisfactory enzyme activity could be attained that promises industrial applications.

Mathematical models used to simulate the water quality and the processes of self-purification of water bodies are important tools to support effective water resource management. The objective of this study was to evaluate the impact of organic pollution on water quality and the assimilative capacity of organic matter in the Ribeirão Vermelho stream situated in the city of Lavras in Minas Gerais. The deoxygenation rate (K 1 ) and reaeration (K 2 ) were determined and tested in three segments of the Ribeirão Vermelho over two seasons (summer and winter). The purification process simulation was performed using the StreeterPhelps model. The highest K 1 and K 2 values occurred during the winter period which was characterized by lower flows. Simulation of the dissolved oxygen profile and biological oxygen demand fitted the model well, indicating the prevalence of carbonaceous deoxygenation due to nitrification and also demonstrating the importance of natural reaeration as part of the purification process. Different response was observed during the winter, in which the high primary productivity values stood in the reaeration process stream. Biological oxygen demand values did not meet the limits recommended by the Resolution of the Ministry of the Environment 357/2005 throughout the river system and the entire study period. In conclusion, the Ribeirão Vermelho is unable to self-purify along its entire length, and water quality is influenced by effluent discharge which intensifies degradation.Keywords: effluent release, Streeter Phelps models, water quality.Coeficiente de desoxigenação, reaeração e potencial de auto purificação de um ribeirão urbano RESUMOOs modelos matemáticos utilizados para simular a qualidade da água e o processo de autodepuração de corpos d'água são importantes ferramentas de auxílio à gestão dos recursos hídricos. Assim, o objetivo deste trabalho foi avaliar o impacto da poluição orgânica na qualidade da água e a capacidade de assimilação da matéria orgânica no Ribeirão Vermelho. Para essa finalidade, foi desenvolvido e testados os coeficientes de desoxigenação (K 1 ) e reaeração (K 2 ), em três trechos e em dois períodos distintos (verão e inverno). Os maiores valores de K 1 e K 2 foram obtidos durante o inverno, onde foram registrados as menores vazões. A simulação do processo de autodepuração foi realizada com o uso do modelo de Streeter-Phelps. A simulação do perfil de OD e DBO no verão apresentou calibração aceitável, tendo em vista a otimização dos coeficientes, evidenciando a prevalência da desoxigenação por demanda carbonácea sobre a nitrificação e a importância da reaeração natural no processo de autodepuração. Comportamento diferente foi observado no inverno, no qual os altos valores de produtividades sobressaíram no processo de reaeração no ribeirão. Apenas o parâmetro demanda bioquímica de oxigênio não respeitou os limites preconizados pela Resolução do Ministério do Meio Ambiente 357/2005, tendo ficado em toda a extensão do rio e, em ambos períodos, fora da regulamentação. Des...

The aim of this study is to determine the potentials of clinoptilolite zeolite in removing selected heavy metals, that are copper and magnesium in aqueous solutions. The removal of both metal cations has been studied by using the batch techniques. Three experimental variables were carried out under predetermined conditions of contact time (20 – 100 minutes), effect of dosage (0.20 – 1.00 gram), and effect of pH solution (pH 2 to 10). Adsorption capacity of zeolite towards heavy metal removal was then determined at various initial concentrations of metal ions between 20 to 100 ppm. Results obtained shows that adsorption of Cu 2+ and Mg 2+ on zeolite has been shown to depend significantly on the pH, adsorbent amount and contact time. The significant value of pH was reached at pH 6, followed by 1 hour of contact time for 1 gram of adsorbent; for both metal ions studied. Studies on the rate of uptake of heavy metal ions by the zeolite indicated that the process was quite rapid and maximum adsorption occurred within the first hour of contact. The results show that high silica zeolite such as clinoptilolite is a promising adsorbent as they combine high adsorption capacities and molecular sieve properties.

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The adsorption capacity of activated clinoptilolite zeolite for the removal of heavy metal ions; iron Fe(III) and manganese Mn(II) from palm oil mill effluent (POME) was investigated in this batch sorption study. The physicochemical properties of both raw clinoptilolite zeolite and POME effluent were first characterized before the modification of the zeolite is made, chemically and physically. The raw filtered POME has an initial pH of 4.56 which was acidic, whereas the natural zeolite has a slightly alkaline pH at 7.52. The effects of pH (5, 7 and 9), sorbent dosage (15, 20 and 25 g in 125 ml of effluent), contact time (15, 30, 45, 60, 120, 150, 180 and 200 minutes) and agitation speed (120, 150, 180 and 200 rpm) on the sorption of heavy metal ions were evaluated. The concentration of heavy metals was analyzed using AAS. The concentration of heavy metal ions for each parameter has decreased significantly after batch study. The adsorption of heavy metal ions increased with the increasing of pH and adsorbent dosages. Optimum percentage of metal removal and the amount of metal ions adsorbed by the zeolite were determined at 85% of Fe(III) and almost 92% of Mn(II) in the experiments.

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Rehabilitation of river ecosystems is generally initiated when a river is no longer able to provide benefits to humans and other living beings. The major purposes of river rehabilitation projects are improving water quality, conserving nature, rehabilitating fisheries and riparian habitats, flood mitigation, and creating recreational opportunities. For a river rehabilitation project to be successful, it must have specific and clearly explained objectives, although these objectives will vary for each project depending upon factors such as economics, public demand, ecosystem benefits, and the like. In this article, we provide a critical analysis of the purposes that drive river rehabilitation projects and we identify and discuss impediments that can cause a project to deviate from its intended goals. We also discuss major constraints on rehabilitation efforts that can result in failed projects.