Difference between revisions of "Team:Aachen/HP/Gold Integrated"

Here, the organism composition that can utilize this sewage settles itself. We do not breed a special species ourselves. Genetically modified organisms on the other hand simply go down after a short period time. [...] They are not competitive enough.– Dr Brands, wver

2nd

Chloride, sodium, and sulfate are not monitored in municipal plants in the region. Therefore, Dr Joerrens and Dr Brands do not see the necessity to work on the sequestration of these substances. In conclusion, all the ions mentioned above are not treated in plants of the WVER and flow into the rivers. Sulphate, however, is indeed problematic for the canal system and the reduced H2S for fouling the sludge. In Dr Joerrens opinion research on sulfate separation is needed, although the concentrations of sulphate are normally not high enough to cause significant problems.

Sulphate is only a problem if we have got that much sulfate, so that we are facing huge amounts of H2S during fouling. We have got dischargers of sulfate, who generally induce inorganic salts, and that is what we are unsatisfied with. Definitely, there is a lot to be done there […]. - Dr Joerrens

Talking about chloride and sodium, Dr Joerrens sustained the insights we got from our research on the current situation in the Werra. Additionally, both Dr Joerrens and Dr Brands reported that de-icer strewed on streets can lead to significantly high amounts of NaCl in a short period of time, disturbing the sedimentation of bacteria.

With chlorides, we do not have problems here in our region. […] It is certainly a problem for the salt and potash mines. If you find a solution to lower the chloride-concentrations there this would be a big thing, because this is a huge issue. – Dr. Joerrens

The flake cohesion is partly dependent on divalent ions such as calcium. These can be "swept out" when de-icer is rinsed on the streets during thawing. [...] These bacteria float, in the worst case, from the secondary clarification into the river. - Dr Brands, wver

The discussions confirmed that our initial idea to integrate yeast into the sludge of wastewater treatment plants is not feasible due to clashes with bacteria and that it is necessary to find solutions on contaminations in the Werra or industrial wastewaters. For these issues, we are best suited. In winter months NaCl can cause issues for municipal water treatment plants, but generally, NaCl is not an issue to care. In conclusion, we will focus our project on industrial applications instead of municipal ones.

The second part of the interviews focused on possible methods to implement our yeast into wastewater treatment. 3 main subject areas were discussed.

1st Breeding conditions of the yeast

As described above we refrained from adding the yeast to the bacterial sludge. Therefore, a separate basin only containing yeast would be needed. In this basin, the yeast would need nutrients, especially a carbon-source. For Dr Brands this is a problem for municipal wastewaters, but not for industrial applications. Wastewaters which contain the nutrients already would additionally lower costs, meaning the easiest way would be to breed the yeast directly in the wastewater.

You need to look for specific branches of industry that have wastewater with the necessary nutrients and sugars for yeasts. As on the sewage treatment plant here with such a sewage mixture, this will certainly not be realizable. – Dr Brands

2nd Separation of yeast from cleaned water

We need to make sure that a genetically modified yeast is not flushed out with the effluent of the water treatment plant. We asked if Dr Brands and Dr Joerrens could think of possibilities to solve this issue. Therefore, we discussed if sedimentation of the yeast, being the most conventional method for bacteria, due to flocculation is realistic. Yeast do not sediment, instead they appeared to float on the water when entering a wver wastewater treatment plant accidentally.

We once had a high induce of baking yeast in one of our smaller sewage treatment plants. […] The floating sludge was then skimmed and fouled. - Dr Joerrens

Obviously, this means that an alternative separation method is needed. Dr. Brands pointed out that there are wastewater treatment plants using membrane technology. In those plants, the bacterial sludge is not separated via sedimentations but via a close-meshed membrane.

Principle of a wastewater treatment plant based on membrane technology for separation compared to a classic treatment plant with secondary clarification based on sedimentation.

For Dr. Brands, membrane separation is more energy-costly but way more efficient then sedimentation, that’s why it is used already nowadays in wastewater treatment plants to hold back, for example, antibiotic resistant strains. In her eyes, this makes it an ideal system for us to investigate.

We have two sewage treatment plants, which are operated with membrane filters. […] In this bacterial sewage mixture, membrane units are placed in the aeration tank, and the permeate, for example, the purified wastewater, is sucked out under vacuum, keeping the biomass back. […] The membrane system can definitely keep the yeasts back. – Dr Brands

In conclusion, we worked on a membrane system to guarantee complete separation of yeast and investigated the balance of energy of this method. Therefore, we cooperated with the RWTH Institute on sanitary environmental engineering as a research group for membranes and General Electric as a producer of membranes.

3rd After-usage of yeast after taking up substances.

Similar to conventional desalination methods for seawater like reverse osmosis or Multi-Stage Flash Evaporation (MSFE) the ions or substances taken up by yeast only assimilate and are not spoilt. This raises the question what to do with the yeast after purifying water.

It seems nearby to re-use the yeast as a nutrient for agriculture. There are two essential problems opposing this solution. First, it is not allowed to spread genetically modified organisms in Germany, meaning the yeast would have to be killed and denaturated, concluding in a yeast extract. Secondly, the yeast extract would contain the substances taken up. It seems feasible to create a NaCl containing yeast extract for feeding since most organisms are dependent on NaCl as well. But what is with yeast containing sulfate or other toxic substances? There is no possibility to spread those substances within feeding stuff. Another possibility for that yeast is burning the cells. A method could collect remaining substances after burning for further use, for example recycling of metals used as catalyzers (Input from Bert van As, Chemelot), or diminish them in a controlled way. However, just burning the cells does not seem to be sustainable.

We utilized the knowledge of the WVER to discuss possible solutions for this issue. Dr Joerrens came up with a thought we have not been thinking about before. On a wastewater treatment plant he has experienced that yeast added to fouling towers had a highly positive effect. Many wastewater treatment plants in Germany operate fouling towers for their excessive sludge. The sludge is drained and then fouled and bacteria produce gas, which is transformed into electric energy. With this, the plant in Düren is able to produce 60% of their energy household. When yeast were added to the fouling tower, the yeasts were degraded by the excessive bacteria, boosting the gas and electric energy production.

“The yeasts were skimmed and fouled. There explosive anaerobic reactions occurred. The organisms in the fouling tower utilized the yeast and produced a lot of gas. This was a positive effect since we got a lot of foul gas that we could convert into electricity. – Dr Joerrens

In conclusion, it seems to be highly sustainable to use the cells for enhanced energy production. A technical implementation would mean that the yeasts are drained and added to the fouling tower afterwards. Thus, the salt is not degraded, but the problem will shift from hard to handle to easier to handle and additionally produce enhanced electric energy.

Together with the WVER we concluded that a separation of desalination and conventional water treatment steps is needed due to competition between yeast and bacteria. Nutrition of the yeast directly in the wastewater would reduce costs. Therefore, we will carry out our further experiments and measurements directly in media containing salt. The yeast can be reused for enhanced gas production during fouling of the activated sludge and burned afterwards, leaving behind dry salt. Membrane technology developed to be interesting for us to separate yeast from the treated water, resulting in the cooperation with the RWTH Institute for sanitary environmental engineering.

The RWTH Institute for Sanitary environmental engineering is researching on new technologies for wastewater treatment and the removal of novel contaminations like pharmaceuticals from wastewater.

Dr Palmowski confirmed the issue of entire isolation of the yeast from the environment. Approached by us on membrane technology and its capability to isolate yeast from wastewater she reacted positively.

A membrane system would definitely hold back the yeast. – Dr Palmowski

Dr Brands, biologist researching for the wver, reported that the energy-consumption of such a membrane system is too costly to be feasible. We confronted Dr Palmowski with the energy balance of membrane technologies. In her eyes membrane systems are ill-reputed wrongly. First systems 20 years ago were highly energy consuming, but research has made them nearly as energy-efficient as conventional methods.

In the meantime, these systems improved drastically. They are nearly as energy-efficient as conventional methods. –Dr Palmowski

Besides this, membrane system offers additional advantages for her: Currently, water treatment plants are facing novel contaminations like antibiotic-resistant strains or microplastic. These contaminations cannot be removed by conventional methods, but by membrane systems. Therefore, Dr Palmowski assumes, that membrane systems will play a bigger role in future.

They have many advantages, and therefore they come, in my opinion, more and more in front. You have spoken about antibiotic-resistant pathogens, or other pathogens, which are refrained as well. You cannot guarantee this with conventional methods. Another issue is the contamination with microplastics. Membrane systems also retain microplastics and all the solids, which is why you can simply follow an ozone system without any disturbing solids. – Dr Palmowski

A modern, energy-efficient, membrane system is a highly promising system to implement microbial dustbins into wastewater treatment, especially because it is already implemented and has proven to be successful in many plants around the world.

Dr Palmowski suggested us to test this system with a simple small-scale experiment. We considered the small-scale experiment to be appropriate when using a membrane actually used in wastewater treatment instead of a laboratory membrane. We contacted a producer of these membranes for further cooperation to set up a corresponding experiment.

Besides talking about membrane technology, we also talked about other topics regarding our project. Interesting for us was the talk about the technical implementation of yeast into wastewater treatment. Dr Palmowski gave us interesting advice on how to breed and cultivate the yeast. She depicted that industrial wastewatersare specific for different industries. Therefore, for Dr Palmoswki there is no golden way to implement our yeast. A sustainable system with regards to breeding of the yeast and their growing capabilities in wastewater, always depends on the composition of the wastewater and the availability of nutrients from own production lines.

There are no standard solutions. – Dr Palmowski

In conclusion, we tested the capability of yeast to grow directly in simulated wastewaters containing NaCl, but did not focus on research on a defined methodology for many industrial applications anymore. Instead of that, we focused on the efficiency of our yeast, their isolation and the after-usage of the yeast. With these answers, we hope to set up tailored and most likely sustainable methodologies for different kinds of users within their own industrial network cycle.

GE Power is producing different membrane modules for different applications in water treatment, all with the aim to purify water from contaminations. Different kinds of membranes exist, depending on their application and especially their specific pore-size. While microfiltration is used to separate larger substances, ultrafiltration is used to isolate microorganisms. Additionally, nanofiltration is capable to isolate larger molecules and ions whereas reverse osmosis will even isolate small monovalent ions like Sodium and Chloride. These different membrane pore-sizes enable a large field of applications with an increasing demand for energy from microfiltration to reverse osmosis. Wastewater treatment plants, using membrane technology nowadays, mentioned by Dr Brands and Dr Palmowski, aim to isolate excessive or pathogenic bacteria from the water with ultrafiltration. Discussions with Dr Palmowski showed that the energy consumption of such a system is not significantly higher than that of conventional sedimentation methods anymore.

We contacted Geert-Henk Koops, Technology Leader for Ultrafiltration and Membrane Bioreactor (MBR), to receive further information on Ultrafiltration membranes and a possible experiment to prove the isolation.

He agreed in the name of GE Power to support us with our project. The cooperation included the allocation of a small-scale membrane module to set up an experiment and additional information on how to set up this experiment.

Technical diagramm of the membrane module we received from GE

Dr Koops confirmed an ultrafiltration method as the method to go with. Secondly, Dr Koops gave us advice on the scale we should aim for with our experiment. His advice was to use a membrane with a surface area of 0.025m2, which appears to be small scale, and a flow of 25 liters per m2 and hour through the membrane. Therefore, we used a flux of:

Assuming a surface area of 300m2 occurring in wastewater treatments plants our setup would create a flux through an industrial membrane of:

This scale will prove the concept of using membrane technology, but will not be able to draw conclusions on the efficiency of the isolation of yeast in industrial scale. To investigate efficiency in industrial scale pilot plants are necessary. Together with GE, we decided to work on a small scale to get meaningful perceptions on the capability of membranes to handle genetically modified yeast.

For the filtering itself there are two possibilities. One the one hand you can have a cross-flow filtration, meaning the water flows parallel to the membrane and the membrane is not clogged. Dead end filtration on the other hand is technically easier but needs regular manual cleaning of the membrane from a filter cake consisting of the cells which are held back.

Together with the advice from Dr Palmowski we decided to use a dead-end filtration. The reason was that we have a comparatively small flux over the membrane with 0.625 liter per hour and keep the experimental set-up simple. With Stephan Sibirtsev M.Sc., we decided on a yeast-water mixture to serve as media for the experiment. With this, we aimed to provide a media for the process which is easy to handle.

yeast soluted in water before (left) and after (right) our membrane experiment.

Another point of interest for us was the set-up of the bioreactor we will use for the experiment. A continuous reactor would be the most realistic approach, but is technically more complex. We decided to prove the separation with a continuous system using our self-made pump to pump 0.625 liters per hour into the bioreactor and squeezing 0.625 liters of water through the membrane using low pressure. To create the low pressure we used a conventional piston pump.

With these inputs from Dr Palmowski (Institute for Sanitary environmental Engineering), Stephan Sibirtsev (RWTH Institute for process engineering) and Dr Koops (GE) we were able to set up the following experiment with the following results: Skizze des Experimentes Bild des Experimentellen Aufbaus Wie das aussehen soll, steht ja quasi im Text davor, deshalb würde ich hier über eine Skizze alles erklären. Die machen wir dann, wenn wir wissen wie es aussieht :D

Results:

The effluent was taken and microscoped for determination of the yeast concentration in the effluent. Additionally, probes of the effluent were centrifuged and the size of the pellets compared.

diagramm (left) and picture (right) of the membrane experiment to proof that yeasts can be cleaned from water easily.

Yeast cells form a filter cake on the membrane, making it necessary to clean the membrane from time to time. The experiment was running 1 hour, pumping 1.25 liters through the membrane. In this time frame no cake developed.

Our results show a separation of up to 100% of the yeast from the water with the help of a membrane module. To affiliate the membrane only conventional methods, which are not prone to maintenance, are needed. It was possible for us to purify the yeast-water mix with a simple bioreactor and energy-efficient pump, whereas direct desalination via membranes (Reverse Osmosis) is highly energy-consuming. (Link: Applied Design) The application of membrane technology to guarantee the isolation of yeast in an industrial application is proven to work reliably. However, the experiment was only in small-scale and running a short period of time, leaving no possibility to discuss the efficiency of yeast isolation in technical scale. To test the feasibility of industrial wastewater treatment with yeast for further use, a pilot plant is necessary.