Biotreatment processes

Using advanced modelling to analyse and optimise process performance

Wastewater treatment processes are used to degrade industrial and municipal organic waste and render it innocuous by converting it to water, CO₂ and disposable sludge.

Wastewate treatment plant

A key challenge in operation of such processes is response to upsets.

By its very nature, at end of production processes, the waste treatment system is subject to wide variation in feed rates and composition.

Because of the dynamics of microbial population growth, difficulties in operation can translate into downtime in the upstream processes with potential significant losses in production.

The dynamics of such processes which give rise to operational difficulties are difficult to predict without rigorous modelling of the chemistry and kinetics.

Detailed dynamic modelling can be used during both the process design phase and afterwards to predict the process response and then optimize equipment and process control schemes.

PSE’s advanced Biotreatment modelling technology gives definitive answers to complex questions:

What is the complete atomic accountability for up to fifty degradable substrates including exact nutrient usage, CO₂ generation, inorganic solid formation and tracking of VOCs?
What is the optimum pH control scheme to minimise reagent usage and promote microbial growth?
How will the process respond to startup, shutdown and shock loads?
How will I optimise the number of bioreactors, their size and the oxygen injection point

The PSE solution

PSE’s solutions for biotreatment are aimed precisely at addressing these challenges. Built in PSE’s state-of-the-art gPROMS process modelling package, PSE's sophisticated biotreatment models provide many unique and powerful features not found in other water treatment software:

The power and flexibility of the gPROMS® environment and the expert ModelCare® consulting support have allowed us to develop a state-of-the-art model for a complex process with minimum time and effort”

Steve Pietsch
Senior Research Associate BP Chemicals, Naperville

Automatic generation of all stoichiometrically-balanced heterotrophic and autotrophic reactions from definition of the substrate(s) alone (via MS Excel).
Estimation of parameters for biochemical kinetics for various reactions from experimental data, including a full statistical significance analysis of the quality of these estimates.
Design of optimal experiments to determine these parameters, aimed at producing the maximum amount of information for parameter estimation and model discrimination from the minimum possible number of experiments.
Dynamic and steady-state simulation of process operation allows you to investigate a wide range of static and dynamic effects.
Rigorous mathematical optimisation to establish optimal designs of treatment units and their control systems, and to derive optimal steady-state and/or dynamic operating procedures while satisfying all important constraints.
Model library. The Bioreactor Library provides standard models, including Bioreactors, Clarifiers and common flowsheet combinations such as those used for conventional activated sludge.
Open models. Unlike other “black box” models, gPROMS allows you to inspect and modify the mathematics describing the chemistry, thermodynamics, kinetics, mass transfer and all other defining equations.
Choice of physical property methods, including the OLI Electrolyte package, Multiflash^® and any CAPE-OPEN package such as Aspen Properties Plus^TM .
Customisation. Users can substitute their own equations, amend the existing equations, or create an entirely new model for a specific proprietary unit.

Biotreatment example

Biotreatment flowsheet

The single-bioreactor process (shown in the gPROMS flowsheet diagram) was executed for a two-substrate process feed.

Plot O2 concentration

The plot shows the dynamic behaviour of the bioreactor startup, with trends for the two substrates and inert and active biomass.

PSE ModelCare service for biotreatment modelling

PSE’s Biotreatment models are typically delivered via our ModelCare solution services, which includes:

a configuration phase, in which PSE consultants work with your process experts to ensure rapid delivery of a detailed process and product model tailored to your application
an optional model validation phase that uses parameter estimation to fit the model to laboratory or plant data, and experiment design techniques to optimise data collection.

PSE can also advise on the use of the validated models for optimisation of process design and operation.