Interview with Dr. Carsten Meyer from the department of wastewater technology

By inventing an sustainable, eco-friendly tube cleanser for every household we also want to know how the public reacts to our project. As the marketing and commercialization of a tube cleanser that one can buy in the supermarket is out of scope due to time limitations, we know that the research we do is not sufficient. Nevertheless we believe that there is great potencial in our genetically modified tube cleanser and we want to know how the public would react to it and what consequences the use of it would have. For this we visitied the Institute of sanitary environmental engineering and water recycling of the University Stuttgart were we had a very interesting interview with Dipl.-Ing. Carsten Meyer from the department of wastewater technology. Furthermore Mr Meyer gave us a tour through the wastewatertreatment plant and explained us all in detail how the cleaning process of the wastewater works. The institute is not only doing research but also actually cleaning the wastewater of the University Stuttgart and parts of the surrounding suburbs.

The iGEM-Team Stuttgart interviewed Carsten Meyer on his opinion and possible range of application regarding a biological drain cleaner for the usage and its effect in wasterwater treatment. Dipl.-Ing Carsten Meyer – abbreviated CM in the following interview – is the Head of the Department of Wastewater Technology of the Insitute for Sanitary Enigneering, Water Quality and Soild Waste Management located at the University of Stuttgart. The German sewage treatment plants can be generally classified into three steps. The first one, is represented by mechanical methods to remove solid, insoluble particles. The following biological step is responsible for the degradation of organic components (including also organic bound nitrogen) by the help of microorganisms. The last step utilizes chemical reactions as oxidation or precipitation to remove chemical components such as phosphor. The sewage sludge resulted by these three steps is then used in digestion tanks for biogas production and, subsequently, is mostly burnt (1).

The Interview

Dear Mr Meyer, what do you relate with the term Synthetic Biology/Genetic engineering?

Well, it is a diverse field that can be used in and is known especially in agriculture and food industry. People often have negative associations to it, as the consequences of the usage of genetically modified products are often not predictable. But it is an important part of our society and environment that has lots of advantages to offer, when we use it wisely. Due to the lack of nutrition one day I think Synthetic Biology will be inevitable.

What is generally your opinion on our biological drain cleaner which is based on a holistic approach using E.coli? CM:

I think it’s a good idea. Whereby, the chemical substances, usually something basic like sodium hydroxide, which are often used for drain cleaners, don’t really destroy anything in a sewage treatment plant. Nevertheless, I think it’s a good idea to try different ways than the usual ones and you never know which further concepts could follow. In a sewage treatment plant, hair usually don’t pose a big problem, however, there are problems of so-called tressings which often build up by hair in pumps or in stirrers of the digestion tanks. If these tressings aren’t removed they can cause defects. If latter can be avoided more easily, that would be great.

These tressings are really a problem which are mainly caused by the household drains?

The main cause for tressings are definitely households. But I must raise the question as well if one always have to use the chemical – or in this case biological – mace. There also exists the good old plunger. (all laughing)

These chemical drain cleaners don’t even contain stuff like sodium hydroxide but also nitrate and aluminum components. Can these substances cause problems, as we already have – e.g. in case of the nitrate – to much nitrate in (German) ground water?

I don’t think that nitrate would cause major problems as most sewage treatment plants, at least the bigger ones, are equipped with a biological step which degrades nitrate. Concerning the aluminum components, I don’t consider that as a bigger problem. Substances as aluminum hydroxide go into the sewage sludge which gets, by the majority, burnt in Germany. However, in some states the sludge is still utilized soil-related as fertilizer. Of course, then the aluminum substances can cause problems as it’s released into the environment. Therefore, it’s good that the government plans to forbid the soil-related sewage sludge utilization.

What are the biggest issues in the wastewater treatment?

We do have a really big issues with wet wipes. Instead of throwing them in the garbage people throw them in the toilet. They are immensely resistable and clog strainer and rakes of the wasterwater plant, so that it can’t work properly anymore. Other than that there are big uses with organic substances from showergel, household cleaner and pharmaceuticals. These organical compounds can’t be cleaned by a wasterwater plant and they reach our environment and waters. We don’t know how these organical and chemical compounds interact with each other and what influences they will have on our environment and eco system.

In the news, they recently talked a lot about blockages caused by fat. Are these blockages really such a big problem?

Alluding to the recent incidence that happened in London? It can happen, of course. So, you asked about fat blockages in pipes, weren’t you?

Yes, about big lumps of fat.

These are possible. However, the main cause aren’t the households but rather commercial and industrial groups. These problems pose if these groups don’t separate fat from the sewage water before it’s led into the canal system. Furthermore, if the canal system is badly maintained, if the canals system is old, if water is missing in the canals, or if the transport velocity isn’t high enough, then it’s quite possible that such fat deposits happen.

Would such fat blockages be an interesting area of attack for our biological drain cleaner?

Yes, I can imagine that.

Great. Our drain cleaner degrades fats, soap residues and hair. Do you think that, by this breakdown synthesized, important amino acids and fatty acids can be recycled?

Only theoretically, that could be possible. But I can’t judge if that would be economically reasonable. Furthermore, I can see also a conflict of interests. If we say, we want to recycle e.g. fats then they are lacking somewhere else. In the course of the process, fats usually go into the sewage sludge and thereby into the digestion tank. These fats are then important for the biogas production. Consequently, there arises the question if it’s favored to recycle single substances with a relative great effort or is it better to utilize these substances in the degradation tank for the biogas production?

Our E.coli doesn’t only degrade hair and fat, furthermore it produces a rose or fir fragrance by using the degraded substances. Would that be something for your sewage treatment plant?

Wow, that are totally new perspectives. (all laugh) Indeed, there are treatment plants which must cover their biological step to avoid odor if a sewage plant is close to a residential area or if an unfavorable wind direction occurs. However, a good treatment plant usually doesn’t smell too much, anyway, it can happen from time to time. And if you can then scent a rose fragrance instead, that would be great!

Supposing that our biological drain cleaner work as we planned. Would you personally use it?

I would test it in any case!