Amro A. El-Baz

Reverse Problem Formulation for Integrating Process Discharges with Watersheds and Drainage Systems

Summary This work introduces a new approach to integrating the discharges of industrial processes with macroscopic watershed systems. The key concept is that environmental quality models (such as material flow analysis) can be inverted and included in an optimization formulation that seeks to determine the maximum allowable target for the process discharges while meeting the overall environmental requirements of the watershed. Because of its holistic nature, this approach simultaneously considers the effects of the inputs and outputs to the watershed (e.g., agricultural, residential, wastewater treatment plants, industrial, and so on) and the various physical, chemical, and biological phenomena occurring within the watershed. An optimization formulation is developed to systematically represent the reverse problem formulation. To illustrate the effectiveness of this approach, a case study is solved to manage phosphorus in Bahr El-Baqar drainage system leading to Lake Manzala in Egypt. The key environmental and economic aspects are addressed and used to screen plant location and discharges.

Anaerobic Co-Digestion of Wastewater Activated Sludge and Rice Straw in Batch and Semi Continuous Modes

Co-digestion of sewage sludge with rice straw may be attractive option from energetic, as well as, environmental viewpoints. In this study, co-digestion of wastewater activated sludge (WWAS) with grinded rice straw at different ratios (0.5, 1.0, 1.5 and 3.0%), straw to WWAS based on weight, was performed using batch reactors. Moreover, a semicontinuous model was developed for sludge digestion and co-digestion with rice straw. The results showed that the co-digestion of WWAS with rice straw improved the carbon to nitrogen ratio (C/N) and consequently increased biogas production compared to sludge digestion. Moreover, total solids, total volatile solids and chemical oxygen demand were reduced by digestion during the reaction time. Furthermore, the biogas yield increased by increasing mixing ratio in co-digester and reached four times at maxing ratio 3.0% compared to sludge digestion. The semi-continuous model showed that the co-digestion increased total biogas amount continuously and methane was the main component in biogas released from digester and co-digester.

Sesame and Broad Bean Stalks: Mixing Characteristics of Chips as a Biomass Fuel for Bubbling Fluidized Bed Combustor

Abstract Mixing and segregation characteristics of biomass particles are of practical importance because the in-bed combustion efficiency of volatile matter affects the vertical location of biomass in bubbling fluidized bed combustor. Sesame and broad bean stalk biomass materials mixed with sand used in this study. The superficial gas velocity, biomass chip length, sand particle size and mass fraction of biomass varied as experimental variables. The mixing and segregation behavior of mixtures were analyzed in terms of mixing index. It was found that the variability in the chip-shape made the sesame chips is quantitatively and qualitatively higher homogeneity and mixedness than the broad bean chips. The optimum overall mixing index for the sesame and the broad bean is around 0.96 and 0.84 at dimensionless superficial gas velocity (U/Umf) of 2.0 (1.40 m/sec) and 2.1 (1.25 m/sec), respectively. It was found that as the mean diameter increased and the sphericity decreased, the mixing quality decreased. The average sand particle size of 371 µm can keep good mixing with biomass chips of both materials, compared with average particle sizes of sand 550 and 700 µm. Increasing the initial biomass mass fraction yields a poor mixing of the investigated biomass stalks.