Assessment of the influence of continuous and intermittent irrigation on greenhouse gas emissions from paddy rice

The impact of two water management practises on Greenhouse Gases (GHGs) emissions from paddy rice fields was investigated. New Rice for Africa (NERICA 2) lowland variety was planted under intermittent irrigation (II) and continuous flooding (CF) water management practises. Two closed gas chambers (GCs) were developed and used for gas sampling from paddy fields and measurement was done conventionally in all the four growing stages of rice. Gas Chromatograph (GH200-9) was used analysing GHGs such as Methane (CH4), Nitrous oxide (N2O), Hydrogen Sulphide (H2S) and Oxygen (O2). Soil analyses were carried out to determine the presence of the following parameters viz: nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), Manganese (Mn) and calcium (Ca). Others are Organic Carbon (OC), Moisture Content (MC), Iron (Fe), Chloride (Cl) and Electrical conductivity (EC) using standard laboratory procedures and ascertain effects of their availability on GHGs concentration levels. From the study, no appreciable CH4 emissions was detected during the four growing stages and under the two water management practises but other GHGs emitted were higher in CF compared with II. Soil nutrients such as N, OC, K and P also contributed considerably to emissions recorded on the two rice fields. The detection of H2S was also an indication that other gases apart from the common GHGs were present in rice fields. Although, CH4 was not detected, other GHGs emitted were more in CF when compared with II which suggested that II be encouraged as a mitigation strategy for reducing impacts of its emissions

Development and performance evaluation of low-cost wastewater treatment plant

A pilot-scale wastewater treatment plant was developed for the purpose of treating wastewaters in south-western Nigeria. The plant, mounted on a roller frame was divided into three sections, viz. wastewater holder, purification chamber and treated water collector. The purification chamber contained three sets of strainers with locally sourced materials which include Azolla pinnata fern, fine sand, chlorine pellets, alum cubes and palm kernel shell charcoal (PKSC). The performance of the treatment plant was evaluated using four different wastewater (WW) sources which were industrial (IW), municipal (MW), domestic (DW) and aquaculture (AW) wastewaters. Sixteen physicochemical parameters and ten metals were monitored in the four WW samples which included temperature, turbidity, electrical conductivity (EC), pH, total suspended solids (TSS), total dissolved solids (TDS), total solid (TS), acidity as CaCO3, total hardness, total phosphorus (TP), total nitrogen (TN), ammoniacal nitrogen, dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), fecal coliform, Escherichia coli and total coliform count. The metals were Na, K, Ca, Mg, Zn, Fe, Pb, Cu, Cd, and Mn. Water quality analysis was done using standard laboratory procedures and results obtained were subjected to statistical analysis. From the results, 100% removal efficiencies were obtained in some heavy metals such as cadmium (Cd) and manganese (Mn) and in parameters such as turbidity, TP, and TN after passing through the treatment plant. The presence of pathogens and microorganisms that were also reduced does not in any way affect its use for agricultural purposes. All other parameters reduced appreciably with results which were statistically significant at P < 0.05. This indicated the high efficiency of the treatment plant in the removal of the water pollutant and heavy metals from the four WW sources considered

Heavy metals and nutrients removal in a batch-fed greywater treatment system planted with Canna indica and Oryza sativa L.

The objective of this investigation was to determine whether Canna indica and Oryza sativa L. plants have the phytoremediation potential for removing heavy metals and nutrients from greywater treated in batch-fed Horizontal sub-surface Flow Constructed Wetlands (HssFCW). The HssFCW had a Hydraulic Retention Time (HRT) and organic loading rate (OLR) of 3 days and 3.96 (g.BOD/m2.day) respectively. Greywater (GW) samples were characterized for electrical conductivity (EC), total nitrogen (TN), total phosphorous (TP), pH, sodium adsorption ratio (SAR), metals (Al, Fe, Mg, Ca) and Biochemical Oxygen Demand (BOD5). The accumulation of metals in the soil and edible parts of plants was evaluated in terms of bioconcentration and translocation factors. Metal concentrations were determined using an atomic absorption spectrometer, while nutrients were by colorimetric method. The result shows that the metals and nutrients were below the WHO allowable limit for treated greywater recycling in agriculture. Nutrient removal was insignificantly different while metal removal was significantly different in the constructed wetlands (CW). The results indicated that C. indica is preferred as a perennial plant with unlimited metal accumulation and high nutrient removals compare to O. sativa L. with a high metal concentration in the above-ground plant tissue and also an annual plant. Keywords: Canna indicagreywaterheavy metalsnutrientsOryza sativa L.phytoremediation Acknowledgments We thank the laboratory staff and assistants for their commitment. We gratefully acknowledge the critical comments and corrections of respected reviewers whose comments and corrections improved this work considerably