There is a growing need for more sustainable wastewater treatment technologies to provide non-conventional water sources. Constructed Wetland systems (CW) are viewed as a low-cost treatment technology with proven treatment efficiency. CWS can treat a variety of contaminants using low energy and natural systems by altering various design parameters. There are two configuration types of constructed wetlands: vertical (VF) and horizontal flow CW (HF). Both configurations have been widely adopted in both large and pilot scale studies with proven records of reasonable wastewater treatment efficiency. The current article reviews the recent development of CW technology and highlights the main achievements and successful applications for wastewater treatment at various locations. The review has indicated that a considerable removal efficiency is attained while using engineered CW systems with variable treatment rates for various pollutants. The treatment efficiency is a function of various parameters including wastewater type, scale dimensions, applied plant and the retention time. The review compared the treatment efficiency for both VF and HF and has revealed that various removal rates of BOD, COD, TSS, TN, TP and NH₄ was attained using both configurations. Yet, the removal efficiency in the case of VF was slightly higher compared with the HF with an average treatment level of 77% and 68% was achieved in both systems, respectively. The review revealed that the CW is an effective and sustainable technology for wastewater treatment with the initial influent level, microbial biofilm, detention time, plant species and configuration among the most dominating parameters that are directly controlling the removal rates.

This study evaluates the structural behavior of aerated autoclave concrete (AAC) blocks laterally loaded in the in-plane direction under quasi-static loading. The study started with the evaluation of the basic physical properties of the AAC blocks, including its structural properties (individually and as part of an assembly), followed by large-scale testing of two (half-scaled) walls constructed with commercially available AAC blocks. The first wall was unreinforced, similar to the commonly used construction technique for low-rise houses where AAC blocks are utilized. The second one was internally reinforced with short dowels connecting the foundation to the walls through their lower block rows and externally reinforced with carbon-fiber-reinforced polymer (CFRP) sheets through the entire wall height. The reinforcement scheme was conducted in such a way that does not delay construction time. Reinforcing the wall significantly increased the strength of the wall in the in-plane direction. The reinforced wall exhibited increased initial stiffness, higher ductility, and larger energy dissipation, in addition to a change in the failure mode. The unreinforced wall failure mode was dominated by blocks sliding, while the reinforced wall failure was dominated by compressive shear failure with wall uplifting. The findings of this study can be implemented to increase the lateral strength of unreinforced new houses and can also be extended to strengthen existing houses built with unreinforced AAC blocks.

This study constitutes a step forward in the overall effort to evaluate the applicability of compressed earth blocks (CEBs) as an environmentally friendly construction alternative in Kuwait. The study is part of a series of experiments that started by assessing different soil samples from various regions in Kuwait. It was discovered that soils in the northern areas (near Al-Sabriyah district and Boubyan Island) contain a good mixture of clayey and silty deposits that can be used to produce CEBs. The collected soil from this region was used in producing CEBs. Three half-scaled walls were constructed and were laterally tested in the out-of-plane direction using quasistatic loading. One of these walls was strengthened using carbon fiber reinforced polymer (CFRP) laminates. A fourth wall made from regular concrete masonry units (CMU) was also tested and compared with the results from the CEB walls. The tests showed the latter had a significantly reduced lateral capacity compared with the wall made from CMUs. It emerged from the test results that a higher percentage of stabilizer in the CEB production enhances the performance of walls made from these CEB in their out-of-plane direction. This is especially the case in terms of stiffness, strength, displacements, and energy dissipated. Results revealed that strengthening CEB walls can alter their structural behavior from flexural dominated to shear dominated failure with an increase of 116 % in the wall strength (nearly doubled) under lateral loading in the out-of-plane direction.