Simulation – the key to innovation
Innovation is a key theme of AMP7, but how can new ideas develop into established technologies? The answer is through a multi-stage process from initial research to full scale implementation, with validation required at each stage.
Joseph P. Martino, a technological forecaster, developed these stages of technological development:
- Scientific findings: Basic scientific understanding of some phenomenon has been developed.
- Laboratory feasibility: A technical solution to a specific problem has been identified and a laboratory model has been created.
- Operating prototype: A device intended for a particular operational environment has been built.
- Commercial introduction or operational use: The innovation is not only technologically successful but also economically feasible.
- Widespread adoption: The innovation has shown itself to be superior in some way to whatever was used previously to perform its function and begins to replace previous methods.
- Diffusion to other areas: The innovation becomes adopted for purposes other than those originally intended.
- Social and economic impact: The innovation has changed the behaviour of society or has somehow involved a substantial portion of the economy.
This article will focus on the early stages of development and especially how laboratory trials can be used to establish proof of concept by simulation of the process at bench or pilot scale.
Aqua Enviro is a specialist wastewater laboratory and consultancy, which has been providing bespoke solutions to the wastewater industry for over 20 years. A core part of our service are our laboratory trials and pilot plants which can be used to simulate a diverse range of processes. The main advantages of these trials are that they are relatively low cost and they are versatile so can easily be adapted to suit a range of process conditions. This means that clients can modify the process or vary different parameters in order to determine the optimum configuration before investing significant capital in a scheme. Because the trials are designed to simulate real-world conditions as closely as possible, the results can be effectively scaled up, meaning that clients can have confidence when using the data to inform the design at the full scale.
The following case studies are examples of some recent projects which illustrate the benefits of simulation over speculation.
Treatability of saline effluent containing agrochemicals
Aqua Enviro are working with a chemical manufacturer to develop a treatment process for their site effluent. The effluent had previously been transported off site for disposal, which was both expensive and environmentally unfriendly due to the number of tanker loads leaving site each week. The effluent was considered difficult to treat due to its high salinity and because of the residual complex organic molecules which were difficult to break down, as well as being biologically inhibitory in some cases.
A batch bench scale study had concluded that COD removal could be achieved using an aerobic process, providing that the effluent was diluted. There was also a recommendation for oxidation to remove the organics left over after the process.
Aqua Enviro operated a continuous bench scale MBR unit in the laboratory for six weeks to validate these theories. The key objectives were:
- Investigate the effects of dilution ratio on removal of COD and key compounds of concern
- Investigate whether the process could deliver any salinity removal
- Provide final effluent samples for evaluation of UV photolysis as tertiary treatment
The trial concluded that COD and organics removal rates of >85% were consistently achieved using the process in saline conditions. During this period, dilution gradually decreased to 1 in 4 and the biomass became acclimatised to saline feed, however there was no discernible reduction in salinity in the effluent.
Owing to the success of this trial, the client has now been able to advance to the next stage of technological development by running a pilot plant on their site.
Inhibition of filamentous bacteria growth in an SBR receiving trade effluent
Aqua Enviro worked with a municipal treatment works which was receiving large volumes of trade waste with a high VFA concentration. The result was a proliferation of filamentous bacteria in the SBR tank which led to a bulking sludge and loss of biomass in the final effluent, thus causing them to breach their consent limits.
Aqua Enviro operated a continuous bench scale SBR unit in the laboratory which trialled different configurations with regards to the feed/aerate/settle cycle. Six test vessels were run as three duplicate pairs and fed with the settled sewage from site over a six-week period. The three variants were:
- Control Scenario
- Extended Fill Scenario
- Anaerobic Fill Scenario
Each reactor was monitored for parameters such as removal of COD/Ammonia/Orthophosphate as well as abundance of filaments. The anaerobic fill scenario performed the best throughout the trial, inhibiting the growth of filaments. The conclusion was that the anaerobic feed phase allowed phosphate accumulating organisms (PAO’s) and glycogen accumulating organisms (GAO’s) to adsorb large amounts of VFA’s, depriving the filamentous bacteria and inhibiting their growth.
The client is planning to modify the operation of their SBR on site and hopefully avoid future breaches of consent.
Supplementary testing
There are a range of other lab tests that can be undertaken in conjunction with more complex simulation trials. These often provide valuable supplementary information. For example, bench scale AD trials are conducted in our laboratory to assess the amenability of a particular feedstock to anaerobic digestion. The AD trial itself is conducted in such a way that the reactor is operated at a representative loading rate and retention time, mimicking real-world operational parameters. The biogas is collected, and the volume generated is used to calculate the proportion of COD broken down in the process. This will tell an operator whether or not a feedstock is suitable to put through an AD process, but this is only half the story. Besides biogas, the other major output from anaerobic digestion is the digestate which can be costly to deal with and needs consideration. An operator can build an effective model for minimising digestate handling costs by having the following tests done.
- Jar testing can be undertaken to determine the optimum type and dose of polyelectrolyte for flocculation of digestate in the dewatering process. Poly is expensive and good flocculation improves dewaterability, so having this information can save an operator money and ensures good performance.
- Using the information from the previous test, the digestate can be processed using our dewatering optimisation tool, DOT. The digestate is treated with the optimum type and dose of poly and then placed inside a permeable membrane before being subjected to sustained pressure to squeeze out the water. The result is a real-world sludge cake and filtrate which is representative of that which would be produced on site. The cake and filtrate are analysed for dry solids and suspended solids respectively, with a high dry solids cake and a low suspended solids filtrate being desirable. This information tells an operator the potential achievable cake quality for their digestate and can be used to calculate likely transport costs.
- The filtrate generated from the dewatering of digestate is often recirculated back to the digester, but it can be high in ammonia and hence can cause toxicity in the digester. It is often preferable to have the filtrate treated in a liquor treatment plant. To check its suitability for biological treatment, the filtrate can first have its inherent biodegradability assessed by carrying out an OECD302B “Zahn Wellens” test. This test measures COD destruction over a 28-day period and the biodegradation curve is plotted over time. As well as this, the filtrate can be tested for any inhibitory properties on the populations of carbonaceous and nitrifying bacteria in a mixed liquor. The results of this test will tell an operator if any dilution of their filtrate is required prior to biological treatment, to nullify any inhibitory effects.
Aqua Enviro can simulate most processes and process conditions with you to answer specific queries or build models to support business cases.
As the poet, artist, and painter, William Blake once said “What is now proved was once only imagined.” It is this kind of thinking that is the key to progressing innovation, and innovation is the best way to overcome new challenges.
To find out more about how Aqua Enviro can help you turn ideas into realities, please call us on 01924 242255 or email enquiries@aquaenviro.co.uk
