Mustafa M. Bob

Aerobic sludge granulation at high temperatures for domestic wastewater treatment

With inoculum sludge from a conventional activated sludge wastewater treatment plant, three sequencing batch reactors (SBRs) fed with synthetic wastewater were operated at different high temperatures (30, 40 and 50±1°C) to study the formation of aerobic granular sludge (AGS) for simultaneous organics and nutrients removal with a complete cycle time of 3h. The AGS were successfully cultivated with influent loading rate of 1.6CODg(Ld)(-1). The COD/N ratio of the influent wastewater was 8. The results revealed that granules developed at 50°C have the highest average diameter, (3.36mm) with 98.17%, 94.45% and 72.46% removal efficiency observed in the system for COD, ammonia and phosphate, respectively. This study also demonstrated the capabilities of AGS formation at high temperatures which is suitable to be applied for hot climate conditions.

Multi-objective Assessment of Groundwater Quality in Madinah City, Saudi Arabia

In this research, a comprehensive assessment of groundwater quality in the city of Madinah, Saudi Arabia was carried out. The main objective was to evaluate whether the groundwater in the city is contaminated by leakage from different sources which will, in turn, give insight into the sources contributing to the shallow groundwater table rise (SWTR) that is observed in many locations in the city. In addition, the assessed groundwater quality helps in determining the most appropriate reuse of the excess water. Out of the 23 wells that were drilled in the study area for the purposes of this study, 20 wells were sampled for water quality analyses. Results showed that the groundwater in the study area is not contaminated by waste water or organic and inorganic compounds or by pesticides and herbicides from excess irrigation of agricultural areas. This suggests that the recent accelerated urban development in the city did not negatively impact the quality of groundwater and did not significantly contribute to SWTR in the city. Lithological description based on soil samples collected from drilled wells revealed the presence of impervious aquitard that extends over the aquifer in the city. This impervious aquitard has most likely played a role in protecting groundwater quality in the study area. Piper and Schoeller diagrams showed that the water type in the study area is a sodium-chloride type with a significant presence of sulfate. Results of this research give useful information about groundwater quality in Madinah city and will help authorities in planning the most appropriate reuse of excess water that may be pumped out to control SWTR.

Observation of Light Non-Aqueous Phase Liquid Migration in Aggregated Soil Using Image Analysis

Physical model experiments were conducted to observe the migration of light non-aqueous phase liquids (LNAPL) in a double-porosity soil medium. The double-porosity characteristics of the soil were simulated through aggregation of kaolin which resulted in well-defined intra-aggregate and inter-aggregate pores. Digital images were collected to monitor LNAPL (modeled by toluene) migration. A special experimental setup was developed to enable the instantaneous capture of the LNAPL migration around the whole soil column using a single digital camera. An image processing module was applied to the captured images and the results plotted using a surface mapping programme. Events observed during the duration of the experiments were discussed. It was found that the LNAPL flowed much faster in the aggregated soil as compared to a single-porosity soil. The wettability of the fluid and the capillary pressure characteristics were demonstrated to be influential factors in immiscible fluids migration when the soil fabric showed highly contrasting porosity values.

Influence of Macro-pores on DNAPL Migration in Double-Porosity Soil Using Light Transmission Visualization Method

Double porosity is a substantial microstructure characteristic in a wide range of geomaterials. It is a natural phenomenon that can be found in many types of soil, and it can result from biological, chemical or mechanical damage. In this paper, the influence of macro-pores on dense non-aqueous phase liquid (DNAPL) migration in double-porosity medium was investigated using light transmission visualization technique. Three experiments were carried out in two-dimensional flow chambers filled with a double-porosity medium composed of a mixture of local sand and sintered kaolin clay spheres arranged in a periodic manner. In each experiment, a different volumetric fraction of macro-pores and micropores was used. Tetrachloroethylene (PCE) was used to simulate DNAPL, and it was dyed using Oil-Red-O for better visualization. A predetermined amount of PCE was injected into the flow chambers and this amount was re-calculated using image analysis. A very strong correlation was found between the PCE amount injected and the amount calculated from image analysis in each experiment. The experiment was repeated by filling the flow chamber with silica sand to represent single-porosity medium. The results show that the macro-pores have a considerable effect on the PCE migration in double-porosity soil as the PCE movement was the fastest in the third experiment which contained the largest macro-pores volume. The accuracy of the method was validated using statistical analysis. The results show a slight difference between the means of the three experiments, indicating that the method is viable for monitoring NAPL migration in double-porosity medium under different volumetric fractions of macro-pores and micropores.

Effect of Operational Changes in Wastewater Treatment Plants on Biochemical Oxygen Demand and Total Suspended Solid Removal

The research presented in this paper investigates the effect of a significant operational change occurred in a wastewater treatment plant in Madinah city, Saudi Arabia on the effluent water quality. The operational change involved the cancellation of the primary settling tanks of the plant, and as a result, the raw wastewater received at the plant directly entered the aeration tanks. The effect of this change on treated wastewater quality as determined by Biological Oxygen Demand (BOD) and total suspended solids (TSS) concentration was evaluated. These parameters were measured for one month before and one month after the cancelation of the primary settling tanks and the average values were calculated. Results showed that the average removal percentage of BOD and TSS in the last month before the operational change was implemented was 89 and 88%, respectively. The average removal percentage for the same parameters in the first month immediately after implementing the operational changes was 91 and 92% respectively, which shows that there is no significant difference in the removal efficiency for these parameters after the operational change. These results indicate that the treated wastewater quality was not affected by the operational change implemented at the plant. Results of this research provide useful information for the authorities responsible for wastewater treatment as well as for the scientific community.

Assessment of the behaviour of soil structure in double-porosity kaolin media using light transmission visualization (LTV) method

Double-porosity is a phenomenon that occurs naturally and can be found in many subsurface media such as rock aquifers, agricultural topsoils and compacted soils. These media have different pore size characteristics that result in different hydraulic properties. Two approaches were used to create the double-porosity soil structure using kaolin clay to be tested in migration of contaminant experiments using light transmission visualization (LTV) method. Aggregated kaolin and sintered clayey spheres mixture were used as the media for the first and second test, respectively. The observation shows that the first approach is not viable for a saturated-porous medium because kaolin particles have disintegrated and turned into emulsion. In contrast, uniform kaolin particles that remain strong and solid have been produced using the second approach. In conclusion, the LTV method is viable to monitor the behaviour of fluids in porous media under different conditions.

Modeling of SBR aerobic granular sludge using neural network with GSA and IW-PSO

This paper presents a modeling technique of sequential batch reactor (SBR) for aerobic granular sludge (AGS) using artificial neural network (ANN). A SBR fed with synthetic wastewater was operated at high temperature of 50 C to study the formation of AGS for simultaneous organics and nutrients removal in 60 days. The feed forward neural network (FFNN) was used to model the nutrients removal process. In this work, inertia weight particle swarm optimization (PSO) and gravitational search algorithm (GSA) were employed to optimize the neural network weights and biases. It was observed that the inertia weight GSA-NN give better prediction of nutrient removal compared with Inertia weight PSO. The performance of the models was measured using the R2, mean square error (MSE) and root mean square error (RMSE).