Municipal wastewater treatment using sequential activated sludge reactor and vegetated submerged bed constructed wetland planted with Vetiveria zizanioides

This study investigated a sequential system consisting of Biological Nutrient Removal Activated Sludge(BNRAS) and Vegetated Submerged Bed Constructed Wetlands (VSBCW). The BNRAS/VSBCW combination removing pollutants from municipal wastewater in a developing country was examined. Wastewater from the anaerobic, anoxic and aerobic zones of the BNRAS was fed into 12 pilot VSBCW consisting of 1000 L plastic tanks having 500 mm deep 10–15 mm diameter granite substrate planted with Vetiveria Zizanioides. Irrigation of macrophytes using effluent from the BNRAS was done after 3 months of planting and the VSBCW effluent analyzed. Wastewater samples were collected and analyzed using standard procedures. Percentage removal of 96.6, 96.93, and 97.21% of COD; 33.33, 85.71, and 92.48% of Nitrate/Nitrite;53.51, 46.45, and 88.78% of Sulphate; and 98.34, 99.72, and 99.6% of TSS were obtained from the anaerobic, anoxic and aerobic zones respectively. Removal efficiency from the anaerobic zone effluent was highest during the study period. VSBCW using locally available macrophytes V. Zizanioides in combination with BNRAS was found efficient in municipal wastewater treatment

Electrochemical and thermodynamic investigation of benzenamine as corrosion inhibitor of austenitic stainless steel (type 304) in hydrochloric acid solution

The inhibiting action of benzenamine (BEZ) on the corrosion of type 304 stainless steel in 3M hydrochloric acid was investigated through electrochemical tests. Results show BEZ to be an excellent inhibitor. The compound was observed to be of mixed type in action. Inhibition efficiency increased with increase in BEZ concentration giving an optimal value of 96.14% at 6.25% BEZ concentration from weight loss and 88.7% at 5% BEZ concentration from polarization tests. X-Ray diffractometry revealed the absence of corrosion products. Statistical analysis using ANOVA showed the statistical significance of BEZ concentration on its inhibition efficiency performance. The compound obeyed Langmuir adsorption isotherm

Analysis of auto-purification response of the Apies River, Gauteng, South Africa, to treated wastewater effluent

The assimilative capacity of water bodies is an important factor in the integrated management of surface water resources. The current study examined the auto-recovery processes of the Apies River from wastewater discharged into it from a municipal wastewater treatment facility, using a series of equations, including the modified Streeter-Phelps equation. Field data obtained include dissolved oxygen (DO), temperature, stream velocity, depth, and width. Water samples were also obtained at 10 sampling stations for the determination of biochemical oxygen demand (BOD) using standard methods. It was observed that the DO and BOD level (5.59 mg/L and 8.5 mg/L respectively) of the effluent from the wastewater treatment facility indicated better water quality than the Apies River background DO level (5.42 mg/L) and BOD level (13 mg/L). Also, at 270 m downstream of the effluent discharge point, another effluent stream (Skinnerspruit) adversely impacted on the Apies River with DO and BOD levels of 6.5 mg/L and 9.0 mg/L, respectively, compared to the Apies River background values of 6.81 mg/L and 8.0 mg/L, respectively. The stream, however, recovered well from both the background and imposed pollution sources as it had a computed positive auto-recovery factor of 1.74. Furthermore, the measured DO deficit was plotted against predicted DO deficit. The plot revealed a close match between the measured and predicted DO deficit, indicating that the model could be used for predicting DO deficit along other segments of the river. To further improve on the natural auto-recovery processes of the Apies River, it was recommended that flow along the Skinnerspruit should be enhanced by clearing the observed aquatic plants growing within the channel. Also, suspected pollution activities taking place further upstream on the Apies River should be investigated and appropriately addressed

Appraisal of access to safe drinking water in southwest Nigeria

The importance of developing effective water supply services is universally recognised as a basis for improving the overall health of the population. This study ascertained the quality of water supplied by a water treatment scheme in southwest Nigeria. One hundred and twelve samples were collected during the wet and dry seasons. Tests on physico-chemical and bacteriological parameters were conducted. Statistical analysis of variance was carried out on the results of the test. The effectiveness of the treatment processes on the parameters considered showed that the aeration, sedimentation and filtration processes were 70.13% effective in colour removal; sedimentation and filtration processes were 94.78% effective in turbidity removal; sedimentation and filtration process were 28.84% effective in the removal of total suspended solids (TSS) and 9.88% effective in the removal of total solids (TS); the disinfection and filtration processes were 100% effective in bacterial and coliform removal. The treatment system was found to be 71.38% effective in pollutant removal

A Model Selection Procedure for Stream Re-Aeration Coefficient Modelling

Model selection is finding wide applications in a lot of modelling and environmental problems. However, applications of model selection to re-aeration coefficient studies are still limited. The current study explores the use of model selection in re-aeration coefficient studies by combining several suggestions from numerous authors on the interpretation of data regarding re-aeration coefficient modelling. The model selection procedure applied in this research made use of Akaike information criteria, measures of agreement such as percent bias (PBIAS), Nash-Sutcliffe Efficiency (NSE) and root mean square error (RMSE) observation Standard deviation Ratio (RSR) and gragh analysis in selecting the best performing model. An algorithm prescribing a generic model selection procedure was also provided. Out of ten candidates models used in this study, the O’Connor and Dobbins (1958) model emerged as the top performing model in its application to data collected from River Atuwara in Nigeria. The suggested process could save software and model developers lots of time and resources, which would otherwise be spent in investigating and developing new models. The procedure is also ideal in selecting a model in situations where there is no overwhelming support for any particular model by observed data

Plastic waste as strength modifiers in asphalt for a sustainable environment

This research took the form of an investigation into the applicability of polyethylene terephthalate (PET) as strength modifiers in asphalt road construction. Samples of thoroughly washed, naturally dried and shredded PET wastes were collected. The optimum binder content (OBC) of the unmodified asphalt mix was determined. The bitumen used for the control mix was replaced with PET waste in 1, 3 and 5% proportions. Another sample was prepared with the addition of 1, 3 and 5% of PET waste while the OBC was fixed. The samples were subjected to Marshall Stability (MS) and Marshall Flow (MF) tests. Bulk density (BD), void in total mix (VTM), and void filled with bitumen (VFB) were determined. The results were compared with standards. The PET content obtained that conforms to the specification in AASHTO, ASTM and Nigeria Federal Ministry of Works standards was found to be 1% addition to OBC by weight of aggregate. This percentage PET content was 15% by weight of bitumen with BD, VTM, VFB, MF and MS being 2.38 kg/m3, 3.33%, 82.20%, 4.00 mm and 17.01 kN, respectively. The 1% PET modified asphalt was found to be useful for pavement construction and reduces the quantity of plastic waste in our environment

Reduction of Traffic Congestion and Carbon Emissions Through Park and Ride Transportation System

Traffic congestion results in low vehicular speed, longer trip time, queuing, and blockage of movement coupled with increased demand of space beyond the road capacity. The transportation sector causes 13% of the emissions of greenhouse gas (GHG). It is a sector which is still developing. The fumes from cars contributes majorly to GHG emission. This work investigated park and ride facility as an optimal means of ameliorating congestion and hectic traffic situation within the City of Tshwane’s Central Business District (CBD) with a view to lowering greenhouse gases and their impacts on the climate. Traffic counts were conducted on heavily congested routes leading to the CBD and structured questionnaires were administered within the CBD. Carbon Dioxide (CO2) emitted by traffic within the City of Tshwane Metropolitan Municipality (CTMM) was estimated and the amount of CO2 to be reduced by using park and ride facilities was determined. Traffic volumes on the selected routes indicated a heavy reliance of over 70% on passenger cars as a mode of entry and exit to the CBD of the city. The survey conducted also showed that about 89% of the people interviewed may be delayed by traffic jams when they are going to work. Fifty-four percent of the respondents indicated intention to use park and ride facilities provided it would guarantee safety, security and reliability. The study also revealed that the use of park and ride transportation system may reduce 96.2% carbon emission by cars traveling along the A Re Yeng Bus Rapid Transit (BRT) line in the city. Park and ride may be further researched for the feeder systems of the A Re Yeng BRT and within townships in the city of Tshwane Metropolitan Municipality

Response Surface Analysis of the Corrosion Effect of Metakaolin in Reinforced Concrete

Concrete is one of the most utilized construction materials. The use of sustainable cementitious material is one of the new trends in concrete technology. Several cementitious materials have been used as partial and full replacement for cement in concrete. These materials have been used in a bid to improve sustainability and reduce production cost. However, the corrosion effect of these materials has been neglected. The experimental research assessed the corrosion effect of metakaolin on some samples of concrete. This was achieved by evaluating the concrete pore solution. The metakaolin was used as a partial replacement for cement at 0, 10, 20, and 30% replacement which gave the optimum mechanical strength. The concrete pore was extracted through mechanical means. The inhibition efficiency of metakaolin in concrete production was assessed using the and weight loss method by inserting the mild steel in artificial concrete pore solution. A reduction in the corrosion rate was observed at higher percentage addition of metakaolin which signifies an improvement in the inhibition of the developed concrete The relationship between the observed parameters was evaluated using response surface methodology. The result of the analysis showed that a unit increase in time would cause a 0.03 increase in the corrosion rate. Additionally, a unit increase in the temperature will have a 0.065 positive effect on the corrosion rate of mild steel. The R2 value showed that about 89.7% variation in the corrosion rate was accounted for by the effect of the independent variable (time, temperature and metakaolin). The outcome of this research will serve as a guide for construction workers, engineers and other researchers on the corrosion effect of this sustainable supplementary material in concrete technology towards the design and construction of sustainable concrete infrastructure

A Review on Corrosion in Concrete Structure: Inhibiting Admixtures and Their Compatibility in Concrete

The development in marine industry and its effort in building bridges has placed a huge demand on reliability and duration of service of reinforcing steel in concrete. Literature has documented several studies on corrosion of reinforcing steel in concrete induced via carbonation and chloride in marine milieus. Extension of concrete structures service life has been one of the foremost strong worries of the concrete industry, especially for marine industry. Hence, the necessity to employ a cost effect system for shielding the reinforced steel in concrete from corrosion. Studies have shown that one prospective solution in combating corrosion deterioration in reinforced steel in concrete structures is the introduction of corrosion-inhibiting admixtures into concrete. This review discussed at length corrosion in reinforced concrete and corrosion inhibitors in relation to concrete together with the classification of inhibitors based on the method of applications. This review further reports corrosion-inhibiting admixtures in concrete. As a result, the aspects of corrosion inhibitors this manuscript reviewed are corrosion inhibitors employed as admixtures in concrete for new construction in the marine industry. Furthermore, corrosion inhibitors are employed for repairs and maintenances admixed with concrete for patches on marine structures, squirted onto the surface of the concrete or put on the concrete surface via saturation treatment. As a result of the excellent properties of functional nanostructured materials, the advancement in the implementation of functional materials in inhibiting admixtures in concrete is fast growing in marine industry. Hence, the Integration of functional materials in inhibiting admixture and their compatibility were reviewed. The significance of inhibitors employed as admixtures in concrete for practical applications of corrosion are the suppression or mitigation of corrosion process of metals used in marine industry and the patches of already constructed structures. The current problems related to corrosion-inhibiting admixtures in concrete and the future research and development directions were discussed