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Liquid phase oxygen supply strategy (LPOS), in which hydrogen peroxide (H(2)O(2)) is used to supply oxygen to the bioreactor, leads to low cell productivity despite high specific productivities of relevant metabolites. We hypothesized that high H(2)O(2) concentrations in the feed-zone led to local cell death, which in turn, lead to lower cell productivity. To test the hypothesis, a mathematical model was developed. Bacillus subtilis 168 was used as the model system in this study. The model simulations of cell concentrations in the bioreactor-zone were verified with the experimental results. The feed-zone H(2)O(2) concentrations remained 12-14 times higher than bulk bioreactor concentrations. The high local concentrations are expected to cause local cell killing, which explains the decrease in overall cell production by 50% at 300 rpm compared to conventional cultivation. Further, among the four different feed strategies studied using the model, dissolved oxygen (DO) controlled H(2)O(2) feed strategy caused least local cell killing and improved overall cell production by 34%.

Urban wastewater management is a crucial challenge in the small and medium towns situated in the developing countries worldwide. These towns are also facing an increasing gap between infrastructure and population growth. A conventional approach to curb these problems is the application of cost-intensive electro-mechanical sewerage technologies, as adopted in developed countries. The first part of this paper derives a set of indicators to framework a sustainable urban wastewater treatment system by reviewing the current state of wastewater management in developing countries, for example, the sample case study being India. The second part evaluates the potential performance of the proposed alternative in-situ hydroponic vetiver system (HVS) against those set of sustainability indicators by reviewing the worldwide performance of the HVS. The objective of this paper is to assess the potential viability of the HVS as a sustainable and cost-effective alternative for developing countries. The current analysis can aid in mainstreaming the use of HVS in policy making and urban planning.

A real time whole plant simulator for process control and optimization (Aquifas+ , Aquifas Plus) was developed using an enhanced version of IWA ASM2d model for mixed liquor and biofilm, together with advanced mathematical algorithms for achieving higher speed and accuracy required for real time operations control and optimization as compared to plant design, algorithms for scenario generation and optimization, and tools for calibration to full scale plants.The simulator works at the desktop and enterprise levels. At the enterprise level, it captures and provides data from multiple plants and feeds information to multiple screens at different locations. This helps utilities that manage multiple plants, pump stations and water and wastewater systems, manage them from one location. The simulator connects and manages data from SCADA, laboratory, and plant inspection and asset management systems. It compresses and stores the data in a database together with data from simulations. It provides feedback to the operators to help them optimize simultaneously for a combination of compliance, chemical use, energy use and greenhouse gas emissions. It does the optimization by generating operating scenarios by varying operating parameters at intervals that are customized to the flow, HRT and needs of each plant. The process model and the simulator are being evaluated as a plant optimizer and controller at plants in temperate and tropical climates in North America, Middle East and Asia.

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