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ABSTRACTThe objective of this research was to investigate existing waste disposal practices and to determine the optimally suitable and acceptable disposal site for Adama town, Ethiopia. The pertinent restrictions identified to realize the objective were slope, river proximity, road, soil type, environmentally sensitive areas, protected zone, and settlement proximity. The criteria were weighted in the GIS environment and then, based on appropriateness of dumping places, the region was classified to different suitability zones. The primary stage solid waste collection is carried out by small and micro enterprises (SMEs) and their service covers more than three-fourth of the households of the town. The waste which is not collected by SMEs is mainly disposed of in environmentally sensitive places. According to the results, only 8.64% (939 ha) of the total area is highly suitable, 27.83% (3026 ha) is completely unsuitable and the remaining 63.53% (6908 ha) is moderately suitable. Four municipal solid waste disposal sites with minimum destructive effects and the lowest environmental impacts are identified to be suitable for Adama Town. Thus, the use of GIS for suitable dumping site location was effective, and the findings will be valuable in maintaining healthy environment and public by realizing dumping plants on the identified site.

Waste in the construction industry is the loss produced by activities that generate direct or indirect costs but do not add any value. In recent years, waste in the construction industry has been the subject of several research studies around the world; however, it still continues to be a critical issue. Thus, the objective of this study was to develop an analytical hierarchical model for the implementation of lean techniques for the reduction of construction waste in real estate companies in Addis Ababa, Ethiopia. The study was conducted on seven private residential real estate companies which were actively involved in the construction sector at the time, by targeting decision-makers as respondents. Analytical hierarchical process-based questionnaires and face-to-face interviews were conducted for the collection of primary data. Thus, comparison-based surveys and data analyses were used to quantify the relative priorities for a given set of alternatives on a ratio scale based on the judgment of the construction professionals. According to the data analyses, poor material handling, poor site management, and frequent changes in the design were identified to be the three most dominant sources of construction waste. It was found that the real estate companies do not have any waste reduction strategies or practices. Furthermore, the concerned professionals have limited awareness of the lean techniques and their implementation. Based on the findings, the construction companies are recommended to give proper attention to construction waste minimization and a huge task is ahead of the policymakers for lean techniques implementation.

Water is one of the most essential natural resources required for all living things. Globally, due to various factors, the volume of wastewater generated and contaminant loads are increasing. Therefore, currently, there is high interest and concern in developing more effective wastewater treatment technologies. Particularly, the emerging electrochemical methods, mainly electrocoagulation (EC), electrooxidation (EO), and the hybrid of both EC and EO, have recently attracted attention as a potential method for treating wastewater due to its wide application and environmental compatibility. In the EC process, different metal hydroxide species are formed. The metal hydroxides (coagulant) aggregate the dispersed particles in the solution, which forms bigger flocs and then is removed by sedimentation. In most cases, EC is not able to reduce the stable persistent organic compounds to below the allowable discharge limits. Also, the EO process is an emerging process where contaminants are removed by oxidizing directly at the surface of the electrode or indirectly by generating oxidants in the solution. However, the main drawback of the EO method is that it is not applicable or requires a long operation time for treating water and wastewater with large amounts of suspended solids. Thus, to use the EO treatment system, the suspended solids of the wastewater have to be removed first by using other techniques. This can be achieved by a hybrid process of EC and EO. Besides, the hybrid process can enhance the removal of COD, TOC, NH4+-N, nitrates, phenol, which is not effectively achieved by using only EC or EO. Therefore, in this particular review, special emphasis was given to a hybrid of EC and EO processes, in addition to assessing electrocoagulation and electrooxidation as exceptional electrochemical methods. Even though several studies have covered EC, EO, and a hybrid process of EC and EO systems separately, to our best knowledge, there is an extremely limited number of review papers that have been done on the hybrid process of EC and EO. Therefore, this manuscript aims to review the potential of a hybrid of the EC and EO processes for treating wastewater generated from various sources.