Valuation of ecosystem services in South Africa, 2001–2019

Please read abstract in the article.The Department of Environmental Affairs (South Africa) and the joint National Research Foundation (NRF) of South Africa and the National Natural Science Foundation of China (NSFC).https://www.mdpi.com/journal/sustainabilityam2022Agricultural Economics, Extension and Rural Developmen

Effect of Interstitial Velocity on the Adsorption of Bacteria onto Soil

The adsorption of bacteria onto soil is affected by the physical and chemical characteristics of the soil and water, the size and morphology of the bacterial cells, and the water-flow characteristics in the soil. The present study focuses on the latter factor by investigating the effect of the interstitial velocity on the adsorption of bacteria onto soil. Columns of 10 cm diameter and 130 cm height, respectively, were packed with a sandy soil. The columns were saturated with water containing nalidixic acid-resistant Escherichia coli as a bio-tracer at three different pH levels. The columns were maintained at 20°C for 24 h before connecting the column outlet to its inlet by a pump in a closed loop. Water containing the biotracer was re-circulated through the column for another 24 h at three different interstitial velocities. Water samples were taken from a sampling tap connected to the pump at 4-h intervals. These samples were analyzed to determine the biotracer concentration. The results show that more biotracer cells were retained in the soil at the lower interstitial velocity. The higher interstitial velocity resulted in higher shear forces which caused more desorption of the biotracer cells from the surfaces of the soil particles. Bacterial adsorption was higher at the acidic pH value. The survival of the biotracer cells in soil solution was also tested at three different pH levels. The results show that no decline in the biotracer concentration occurred during the test period

Urban Rainfall Harvesting to Alleviate Water Shortages and Combat Desertification in the Arid Land of Jordan

Abstract: Water harvesting can alleviate the chronic water supply shortages in Jordan, increase cropping land area, improve the livelihood of population and eventually combat desertification. A systematic study was undertaken to evaluate the use of rooftop rainfall harvesting in urban areas, study the socioeconomic value, determine the optimum rainfall collection tank volume and the potential contribution of rainfall harvesting to the national domestic water supply budget. The potential water supply volume from rooftop rainfall harvesting can reach 14.7 million m 3 /year, comprising of about 6% of the domestic national water supply. Analysis of domestic water supply rate in relation to average rainfall depth and number of cisterns in each governorates indicated that the public water supply rate decreased in governorates with high rainfall depth and large number of cisterns. Cistern number among governorates increased with rainfall depth indicating a good adaptation behavior to water shortages. Optimum cistern volume charts were constructed for some governorates as a function of family consumption rate and house roof area. These charts can be used as tool to determine the optimum rainfall cistern volume as related to consumption rate and rooftop area. An immediate and nationwide awareness and legislative program is needed to spread rooftop rainfall harvesting among the whole population of Jordan and region with similar climates

Field evaluation of sand-ditch water harvesting technique in Jordan

Water harvesting is viable alternatives for rainfed agricultural production in semiarid lands. A field experiment was conducted to evaluate the efficiency of a relatively new water harvesting technique, called sand ditch, for moisture and soil conservation. Twelve field plots of 10 m x 2 m were constructed in two adjacent fields having silt loam soils but varied in soil depth, 0.75 m and 2 m, and slope of 10% and 12%. A 130 L barrel was installed at the downslope end of the plots to collect water and sediments at the end of each rainstorm along the rainy season. Three types of treatments were used in duplicates (12 plots in total); sand-ditch plots in which a ditch of 2-m long, 1 m wide and 0.8 m deep was constructed in the middle of plots across the slope (2 in each field), two compacted plots and two plots covered with plastic mulch in addition to four control plots, 2 in each field. The total amount of runoff, sediment concentration, total infiltration and sediment loss for the experimental plots were measured or calculated after each storm during the winter season 2004/2005. Experimental results showed that sand-ditch technique significantly reduced runoff and sediment loss and increased infiltration and soil moisture compared to control or compacted plots. The overall average runoff and sediment reductions in the sand-ditch plots were 46% and 61% compared to control plots. Sediment losses from compacted plots were about 2.2 and 6 folds higher than control and sand-ditch plots, respectively making soil compaction unsuitable technique for rainfall harvesting under the current experimental and climatic conditions. Construction of sand ditch also increased the dry matter yield of native grass by an average of 62% and 40% in the two experimental fields compared to control.Runoff Soil loss Rainfall harvesting Soil moisture Semi-arid land

Integrated environmental management and GPS-X modelling for current and future sustainable wastewater treatment: A case study from the Middle East

In the context of today's rapidly changing environmental challenges, accurately predicting the performance and efficiency of environmental management strategies is crucial. Particularly in the Middle East, where research on wastewater treatment plants (WWTPs) is notably lacking, addressing this need is imperative. This study investigates the treatment efficiency of a wastewater treatment plant and proposes various techniques to enhance its performance. Employing a case study method, we utilise the GPS-X model to forecast the plant's performance under diverse scenarios, offering solutions for future challenges. The results reveal that the current plant layout operates efficiently, with removal efficiencies for Total Suspended Solids (TSS), Chemical Oxygen Demand (COD), and Biochemical Oxygen Demand (BOD) at 98.3 %, 95.1 %, and 96.1 %, respectively. The outlet Dissolved Oxygen (DO) of 1.9 mg/L meets local wastewater reuse standards. Furthermore, the GPS-X model forecasts the plant's performance under different scenarios, suggesting the feasibility of a new layout within 20–25 years and the need for additional units after 40 years. As inflow approaches maximum design capacity, simulation results underscore the importance of utilising the full plant design and expanding it for optimal operation over 60 years. This research provides critical insights for improving WWTP performance and emphasizes the significance of strategic planning in addressing long-term environmental management challenges. Moreover, this study represents a pioneering effort in addressing critical water scarcity challenges in Jordan by exploring the potential of treated wastewater (TWW) as a sustainable solution, thus contributing to the advancement of environmental management practices in the region

Enhancing Water Infiltration through Heavy Soils with Sand-Ditch Technique

Enhancing rainwater infiltration into heavy soils is an important strategy in arid regions to increase soil water storage and meet crop water demand. In such soils, water infiltration and deep percolation can be enhanced by constructing deep ditches filled with permeable materials, such as sand. Laboratory experiments were conducted to examine the effect of sand ditch installed across the slope of a soil box, 50 × 20 × 20 cm3, on runoff interception and water infiltration of clay soil packed at two bulk densities, 1240 and 1510 kg/m3. The experiments were carried out under laboratory conditions using simulated steady flow of about 20 cm/h for a duration of 60 min. Results showed that sand ditches highly reduced runoff and largely enhanced water infiltration into soils. In low-density soil, the average runoff was 15% of inflow volume but reduced to zero in the presence of sand ditches thus increasing soil water storage by 15%. In high-density soil, the presence of sand ditches was more effective; infiltration volume increased by 156% compared to control. The WASH_2D model was used to simulate water flow in the presence of sand ditches; it showed to increase water infiltration and soil-moisture storage thus improving crop production in drylands

Estimation of surface depression storage capacity from random roughness and slope

Depression storage capacity (DSC) models found in the literature were developed using statistical regression for relatively large soil surface roughness and slope values resulting in several fitting parameters. In this research, we developed and tested a conceptual model to estimate surface depression storage having small roughness values usually encountered in rainwater harvesting micro-catchments and bare soil in arid regions with only one fitting parameter. Laboratory impermeable surfaces of 30 x 30 cm2 were constructed with 4 sizes of gravel and mortar resulting in random roughness values ranging from 0.9 to 6.3 mm. A series of laboratory experiments were conducted under 9 slope values using simulated rain. Depression storage for each combination of relative roughness and slope was estimated by the mass balance approach.  Analysis of experimental results indicated that the developed linear model between DSC and the square root of the ratio of random roughness (RR) to slope was significant at p < 0.001 and coefficient of determination R2 = 0.90. The developed model predicted depression storage of small relief at higher accuracy compared to other models found in the literature. However, the model is based on small-scale laboratory plots and further testing in the field will provide more insight for practical applications