Flow control for optimising growth of microorganisms
Today, more than ever, enzymes and microorganisms are being used to increase sustainable production. This is particularly true in industries such as pharmaceuticals and (bio)chemicals. In these and other industries, researchers within universities, R&D organisations and other institutes, as well as within industry want to know under which conditions these biological cells grow. While it is essential and important to know how and under what conditions they grow faster, researchers need the full story. That means they are just as interested in what makes them grow slower or abnormally. It is also essential to learn about the influence of nutrients or additives to understand the underlying biological processes.
For research organisations the accurate measurement and control of low flows of liquids and gases is often required. What is low flow? The real values will be application dependent but might be as low as 0.014 to 0.7 mL/min of N2 to around 600 kg/h in liquid applications.
Bronkhorst excels in this arena and their customers are many and varied. In the area of biological cell growth, for one recent application the organisation sought to learn more about the conditions under which a population of microorganisms will grow. Flow control was used to give an accurate and steady flow of aqueous liquid while they varied an array of other parameters.
It was essential for them to investigate under which conditions a population of microorganisms can grow. For this they would vary one typical parameter, whilst other parameters, such as temperature, pressure and nutrient concentration, needed to be kept constant.
For this recent application, a research organisation contacted Bronkhorst. They had an application where they were struggling to stabilize the low flow in an aqueous stream — in this case their range was 30 to 200 mL/min. They had two reactors that needed to be kept in balance. They had tried to find a balance but were regularly emptying one of the reactors. To that end, their desire was that the liquid levels of two reactor vessels containing these microorganisms needed to be accurately and repeatably kept at a stable, constant value using flow control.
After consideration, Bronkhorst supplied two of their liquid mass flow instruments. In this case it was their mini CORI-FLOW series. The CORI-FLOW series uses the Coriolis effect which was first postulated as an explanation of the deflection of flowing air moving in a rotating system. In fact, the Coriolis effect is a mass inertia effect. A Coriolis-based mass flow meter is particularly suitable when you want to measure the mass flow of varying or unknown gas or liquid mixtures or for measuring supercritical gases. Besides measuring direct mass flows which eliminates inaccuracies due to the physical properties of the fluid, these devices are highly accurate and have a high repeatability. The Coriolis flow meter is the ultimate flexible, reliable and extremely accurate flow meter.
In this application, each CORI-FLOW was inserted in the circulation system in between the reactor vessels, with the aim to provide a continuous flow of aqueous liquid.
The main reactor was approximately 1 litre and the researchers allowed the micro-organisms to grow in the reactor within an aqueous environment. Regular sampling of the main reactor gave them information of the number of cells and the cell growth rate. The researchers also identified temperature as an important parameter. Too low temperatures will hold back the microorganisms and slow or stop them from growing, and too high temperatures are detrimental to the longevity of the microorganisms themselves.
For this sophisticated application, the liquid mass flow instrument with a control valve provides a signal to a control unit. That control unit is ‘in charge’ of a pump. The pump speeds or slows in response to the flow measurement and the control action, making for a very precise flow in this line. From there the liquid then flows from the main reactor to a second reactor. In this case the second reactor is much smaller than the main reactor and has a volume of about 200 mL. Using the same methodology, the fluid is again moved via the direct control pump scenario, described above, back to the main reactor. What is now set up is a continuous circulation, in which the flow is very steady. The process continues day and night for as long as the research requires.
While it sounds like smooth sailing, a further complication was identified. The microorganisms in this experiment were approximately 3 μm diameter. That provided a further challenge as all the microorganisms needed to be kept alive and they needed to be in perfect health (without any damage) during the process of circulation. For this Bronkhorst advised the researchers to use peristaltic pumps in their process to keep their microorganisms fit and healthy.
The Control Unit/s and setpoints were run within the research organisation’s systems; however, it was further determined that, in this application both the flow controller and pump combinations would best have the same capacities. This simplified the operation and helped the levels in both reactors remain at the same, stable value.
Bronkhorst’s flow meter range includes:
Thermal Mass Flow meters & controllers for gases and liquids
Coriolis Mass Flow Meters & Controllers for gases and liquids
Ultrasonic Meters for liquids
Pressure Controllers for gases and liquids
Control Valves and Control Electronica and accessories
In this case the correct flow meter was a Coriolis-based mass flow meter. This technology is particularly suitable when you want to measure the mass flow of varying or unknown gas or liquid mixtures or for measuring supercritical gases. The fundamental theory for a Coriolis meter is direct mass flow measurement. There are no estimations or assumptions or inaccuracies due to the physical properties of the fluid. A CORI-FLOW from Bronkhorst is thus highly accurate and they have high repeatability. For many users, the Coriolis flow meter is the ultimate flexible, reliable and extremely accurate flow meter.
The original article was published as an Application Note by Bronkhorst High-Tech B.V.
A first line of defence in wastewater screening
Two Queensland councils* have opted for Australian-manufactured screening technology to protect the efficiency of their wastewater treatment plants (WWTPs).
In choosing horizontal in-channel rotary drum screening technology engineered by CST Wastewater Solutions, the councils also sought to curtail risks of process and environmental spills from blockages.
CST Wastewater Solutions’ full stainless steel drum technology — with fine pre-screening down to 200 µm — provides a first line of defence against detritus in municipal and industrial wastewater streams entering vital water treatment processes within the WWTPs involved.
The company explained that an integral part of its new, locally manufactured rotary drum screens and auger extractors is industry-best screening, which provides 50% finer apertures for greater waste-solids extraction and recovery.
Drum screens reduce maintenance costs and extend equipment life by preventing clogging and build-up of solids, and prevent the formation of filtrate crusting on the primary clarifier, which is essential for the treatment plant to operate optimally.
CST Wastewater Solutions Managing Director Michael Bambridge said the in-channel (or in-tank) drum screens are custom-engineered for unique local conditions, including widely varying flow rates and inflow content. He added that the systems also recognise the need to cater to municipal and industrial companies that cannot afford to have large in-house engineering and maintenance teams.
One of the latest Queensland installations involved twin screw screens, constructed from full 316 grade stainless steel, with each screen capable of handling 230 L of inflow a second. The Australian-manufactured screens replaced imported screens that were less than 10 years old.
“The second twin-screen installation, with fine drum screening down to 3 mm and 400 L/s capacity, was installed by a major utility operating in a marine environment that was impressed with the performance and durability of existing CST screening technology,” Bambridge said.
“Existing high performance, low maintenance and, importantly, the prompt availability of local service expertise were among the prime reasons for this major authority introducing further CST technologies to maintain and enhance the performance of a WWTP operating in a marine environment,” he added.
CST has drum screens with holes as fine as 2 mm that have been operating for more than 10 years in Queensland.
Bambridge said that rather than opting for one-size-fits-all imported technologies — with potential downtime and supply chain issues when they need service — many local authorities and industrial WWTP operators value the availability of local engineering expertise.
“Good local service is an essential complement to good equipment. Imported equipment is always at the mercy of supply chain delays and cost. Such equipment could be useless the first time it broke down, until it is repaired,” he said.
“Then, both municipal and industrial organisations face the risk of non-compliance of licence conditions and downstream blocking, flooding, production interruptions, and environmental and groundwater hazards.”
CST has been progressively moving towards Australian manufacturing since COVID affected supply chains. It has now achieved full Australian design and manufacture of the following ranges:
Internally fed rotary drums — Model RDs
In-channel horizontal rotary drum — Model FS
Screw screens and associated equipment — Model SF
*The municipalities cannot be named for client contractual reasons
Top image caption: Drum screens are installed to remove solids from wastewater, protect downstream equipment and improve efficiency. Images courtesy of CST Wastewater Solutions.
‘Flow’ Follows a Courageous Black Cat Navigating a World Suddenly Plunged Underwater
When a brave black cat’s world is turned upside down after a massive flood, its courage and wits are put to the test.
Do stories and artists like this matter to you? Become a Colossal Member today and support independent arts publishing for as little as $7 per month. The article ‘Flow’ Follows a Courageous Black Cat Navigating a World Suddenly Plunged Underwater appeared first on Colossal.
Safeguarding Natural Areas Can Protect Cities From Flooding, Canadian Study Finds
All over the world, floods have been increasing in frequency and intensity due to climate change. A new study led by researchers at University of British Columbia (UBC) shows that protecting key ecosystems across Canada could reduce the risk of flooding in over half of urban areas in the country that are at high risk. […]
The post Safeguarding Natural Areas Can Protect Cities From Flooding, Canadian Study Finds appeared first on EcoWatch.