Hydraulic Modelling and Optimization of a Wastewater Treatment System for Developing Nations Using Computational Fluid Dynamics

Waste stabilization pond (WSP) is globally one of the most popular wastewater treatment options because of its high efficiency and low cost. However, no rigorous assessment of WSPs that account for cost in addition to hydrodynamics and treatment efficiency has been performed. A study was conducted that utilized Computational Fluid Dynamics (CFD) coupled with an optimization program to optimize the selection of the best WSP configuration based on cost and treatment efficiency. Several designs generated by the CFD/optimization model showed that both shorter and longer baffles, alternative depths, and reactor length to width ratios could improve the hydraulic efficiency of the ponds at a reduced overall construction cost. In addition, a study was conducted on the optimized WSP which consisted of an anaerobic, facultative, and a maturation stage whose baffle orientation, length to width ratio, was specified by a CFD model prediction and was compared with a three stage WSP designed according to literature suggested reactor geometric configurations. Experimental tests were performed on a pilot scale version of the threestage WSP where the removal performance was based on a number of parameters (Faecal coliform, pH, TDS, and Conductivity). Results showed that the significantly lower cost design based on the optimized CFD simulations displayed slightly better removal performance compared to the standard WSP design developed from literature data. The results of this study clearly showed that unit treatment process designs based on rigorous numerical optimization can aid in producing cost effective designs that make it more possible for developing nations to incorporate adequate and effective sanitation

Water use and grain yield response of rainfed soybean to tillage-mulch practices in southeastern Nigeria

Despite the agronomic, economic and food values of soybean (Glycine max L. Merrill), there is still dearth of information on the tillage need and the implications of surface mulch for the crop in the eastern part of the forest-savanna transition zone of Nigeria. This study was therefore carried out on a sandy loam Ultisol at Nsukka with a sub-humid climate, during 2006 and 2007 cropping seasons. Our objective was to devise an appropriate tillage method for the crop from evaluated effects of no-till (NT), conventional tillage (CT) and mulch on selected key agronomic indices. Each of the NT and the CT was either unmulched (U) or mulched (M) in a split-plot, giving four treatments/tillage methods (NTU, NTM, CTU and CTM) randomized in four blocks. Rainfall was more favorable in the first than in the second season. The mean seasonal soil water storage (range, 99-109 mm) within 0.5-m soil layer differed among the treatments (NTU < CTU < NTM = CTM). However, for the first and second seasons, both water use (582-616 and 667-709 mm respectively) and grain yield (0.71-0.81 and 1.22-1.91 Mg ha-1 respectively) were not different. Mulch lowered the crop water use but had no influence on grain yield. Water use efficiency was enhanced with mulch only in the second season. Although either of the two mulch treatments (NTM/CTM) would be suitable for growing soybean especially in years of unfavorably distributed rainfall, NTM is a more rational choice than CTM. Rainfall adequacy at the critical reproductive stage of the crop showed to be a more important yield factor than the tested tillage methods

CHEMICAL EXAMINATION OF PIPED WATER SUPPLY OF ILE-IFE IN SOUTHWEST NIGERIA

This study was undertaken to determine the changes in the physico-chemical properties of piped water supplied in the state, between the treatment plant and points of use in Ile-Ife, Nigeria. Thirteen samples of water were collected at different locations from treatment plant to the points of use and analyzed for the following selected parameters: alkalinity, total dissolved solids, total suspended solid, total solid, potassium, sodium, calcium, magnesium, trace metals, sulphate and chloride. The results revealed that between treatment plant at Ede and the point of use, there are changes in the considered physico-chemical properties of the water supply.The most significant is the concentration of lead ion which was higher than the recommended 0.01mg/L by the world health organization and total alkalinity with a mean value of (325.36±81.85) mg/L. The study concluded that the treatment process needs to be reviewed to identify the possible source of the ion and put necessary prevention procedures

Runoff water harvesting for dry spell mitigation for cowpea in the savannah belt of Nigeria

Cowpea yields obtained by smallholder farmers in the savannah belt of Nigeria are often less than the maximum obtainable yields because water deficit during critical growth stages is a common occurrence. Runoff harvesting to supplement direct rainfall may prove beneficial in improving current smallholder farming systems in this region. We study the effects of macro- and micro-catchments runoff harvesting, with or without in situ soil conservation, on cowpea yield in the savannah belt of Nigeria. The macro-catchments runoff harvesting (RH) experiment consisted of four treatments: conventional tillage and RH (CRH), zero tillage with RH (ZRH), reduced tillage with RH (RRH) and the direct rain fed (DR) treatment which served as the control in a randomized block design with four replicates. The micro-catchment experiment consisted of four treatments: runoff harvesting (RH), semi-circular bunds (SC), semi-circular bunds with runoff harvesting (SRH) and also direct rainfed (DR) in a randomized block design with four replicates. Results suggest that runoff harvesting can be used with existing conservation techniques. Applying harvested runoff water through supplemental irrigation provides the twin benefits of alleviating the prevailing slack periods and improving the yields of smallholder farming systems.Supplemental irrigation Water deficit Macro- and Micro-catchments Semi-circular bunds Smallholder farming systems Conventional tillage

Eficiência de utilização de água e nutrientes em plantas de feijão-de-corda irrigadas com água salina em diferentes estádios de desenvolvimento Water and nutrient use efficiency in cowpea irrigated with saline water at different growth stages

O objetivo deste trabalho foi investigar os efeitos do uso de água salina em diferentes estádios de desenvolvimento de plantas de feijão-de-corda sobre a eficiência de utilização de água e de nutrientes. O experimento foi conduzido no campo e obedeceu ao delineamento em blocos ao acaso, com cinco tratamentos e cinco repetições. Os tratamentos empregados foram: T1 - água de poço com condutividade elétrica (CEa) de 0,8 dS m-1 durante todo o ciclo; T2 - água salina (CEa de 5,0 dS m-1) durante todo o ciclo; T3, T4 e T5 - água salina de 0 a 22 dias após o plantio (DAP), de 23 a 42 DAP e de 43 a 62 DAP, respectivamente. As plantas dos tratamentos T3, T4 e T5 foram irrigadas com água de poço nas demais fases do ciclo. Aos 8; 23; 43 e 63 DAP, as plantas foram colhidas e determinaram-se a matéria seca total e de grãos, a eficiência no uso da água, considerando a produção de matéria seca total (EUA P) e a produção de grãos (EUA GR), e a eficiência de utilização de nutrientes (K, Ca, N, P, Fe, Cu, Zn e Mn). A aplicação de água salina durante todo o ciclo (T2) reduziu a EUA P e a EUA GR, enquanto a aplicação de água na fase inicial do ciclo (T3) reduziu a EUA GR e a eficiência de utilização da maioria dos nutrientes. Por outro lado, a irrigação com água salina dos 23 aos 42 DAP (T4) e dos 43 aos 62 DAP (T5) não afetou as eficiências nos usos de água e de nutrientes.<br>The objective of this paper was to evaluate the effect of the saline water applied at different development stages of cowpea plants, on water and nutrient use efficiency. The experiment was set up in the field, during the dry season. A completely randomized block design, with five treatments and five repetitions was adopted. The treatments studied were: T1 - (groundwater with electrical conductivity (ECw) of 0.8 dS m-1) during the whole crop cycle; T2 - saline water (ECw = 5.0 dS m-1) during the whole crop cycle; T3, T4 and T5 - saline water from 0 to 22 days after sowing (DAS), from 23 to 42 DAS and from 43 to 62 DAS, respectively. The plants of T3, T4 and T5 were irrigated with groundwater in the remaining stages of the crop cycle. At 8, 23, 43 and 63 DAS the plants were harvested and the total dry mass and grain yield were measured. The water use efficiency was estimated by using total dry mass production (WUE P) and grain yield (WUE GR), as well as the nutrients use efficiency - NUE, (K, Ca, N, P, Fe, Cu, Zn and Mn). The application of saline water during whole the crop cycle (T2) reduced WUE P and WUE GR, while the use of saline water during the germination and initial plant development (T3) caused reduction in WUE GR and in the NUE for most of the analyzed nutrients. Irrigation with saline water from 23 to 42 DAS (T4) and from 43 to 62 DAS (T5) did not affect water and nutrient use efficiencies