Adam Hudson

Aspects of an expert design system for the wastewater treatment industry

A new computer aided design program has been created, which uses computer modelling and simulation techniques in order to automatically generate a design solution for a High Recirculation Airlift Reactor (HRAR) wastewater treatment plant. This program replaces a set of programs which could only be used by process design experts, as many decisions had to be made whilst using the design system. A new expert system is being created to automatically integrate expert knowledge into the design process. This expert system will sit above the design program and control the design process. The objective of the new work presented here was to investigate methods for implementing this new expert system onto the new design program. This consisted of creating prototype software in order to demonstrate the advantages of applying expert systems methods to the design of the HRAR treatment process. This paper introduces the approach taken to acquiring and formulating the expert knowledge, and presents simple software to demonstrate the approach.

A specific blackboard expert system to simulate and automate the design of high recirculation airlift reactors

This paper describes a new specific blackboard expert system to simulate and automate the design of high recirculation airlift reactors. The research work described aims to bring about savings in construction and running costs by automating the design process and removing unnecessary conservatism from the design process. Blackboard expert systems are reviewed and the paper describes the work to create a new blackboard framework for designing high recirculation airlift reactors. Two prototype programs were created in order to test the feasibility of a blackboard architecture expert system for this application and these are described. The testing of the two prototype programs led to the creation of a new expert system that interacted with industrial design programs. Expert design knowledge concerning the design of high recirculation airlift reactors was acquired and this process and the knowledge that was captured are described. Methods used to categorise and represent this knowledge are presented and the operation of the new blackboard system is discussed.

Automating the design of high-recirculation airlift reactors using a blackboard framework

This paper describes work completed in creating a new prototype blackboard framework to automate the design process used for the design of high-recirculation airlift reactors. The new expert system framework encompasses the design programs but does not require any further modification. It aims to automate the design process and make the process more efficient. The paper begins by describing high-recirculation airlift reactors and continues by considering the function of the new framework and presenting the new framework. Components of the new system are described in terms of its function and implementation. Initial testing is described and the results are presented.

Simulation of a high recirculation airlift reactor for steady-state operation

This paper describes a new mathematical model of the fluid dynamic processes in a high recirculation airlift reactor. The model was created to provide information to assist in the design of a reactor, in particular considering the selection of parameters to adjust in order to achieve a steady state solution. The modelling of two phase-flow of air and water in small scale airlift bio-reactors is considered. This modelling was applied to the high recirculation airlift reactor process. A new computer simulation was created and a test program performed to evaluate the models used. The results of this evaluation are presented. The evaluation showed that variation of the superficial gas velocity or the simultaneous variation of the downcomer and riser diameters could be used to produce a steady-state design solution.

Prediction of flow rates and stability in large scale airlift reactors

Large-scale High Recirculation Airlift Reactors have been used to treat biodegradable waste waters since the mid nineteen seventies. The system is particularly attractive for situations where the land to locate wastewater works is restricted. Little is known, however, about the fluid dynamics of the gas-liquid mixture flowing around the reactor. This makes the determination of air injection rates difficult if effluent quality and dynamic stability are to be maintained. When the air injected is not sufficient to maintain stable operation the reactor contents may reverse violently resulting in down time, failure to achieve target discharge quality and possible damage to the reactor itself. As a result many reactor installations operate at air injection rates above those necessary for the biological processes. The extra air injected results in higher capital and process costs. This paper considers the effect of air injection rates on the hydrodynamic stability of Airlift Reactors and a two-phase model is proposed to predict stable operation at a reduced air injection rate. Results are presented which show the effect of reactor design on stability.

Computer modelling of single sludge systems for the computer aided design and control of activated sludge processes

The initial work for the creation of a new automatic CAD system for advanced effluent treatment processes is presented. The creation of a computer model for a completely mixed aerator is described. The computer model consisted of two interacting non-linear differential equations, which were linearised to give an approximate computer model. Optimal control theory was applied to the design of a controller for this system and a series of experiments examined the system performance using both the new computer model and the new controller.