Hockenheim, located in the Upper Rhine lowlands, is worth a visit not only for its race track and fantastic nature. But residents recently turned up their noses because sewer odors dampened their spirits. The city took the initiative: a solution was found within a very short time.
The civil engineering department drew attention to the situation early on: the dirt load in the residential and commercial wastewater led to unpleasant odors from the sewer system, especially in the warm months. When residents also complained to the local council group, the measure was full. “We had to act,” Reiner Lenz recalls.
Standing time and heat
His civil engineering department knew about the cause of the mess. “Organic compounds with sulfur, nitrogen, oxygen as well as hydrocarbons form a cocktail that leads to emissions even after a short dwell time in the sewer,” says Lenz. The temperature in the channel is relevant: the higher, the greater the effect. Inorganic substances such as ammonia and hydrogen sulfide would be particularly noticeable. “They make up the typical wastewater odor”.
It was known from other municipalities that they had already experimented with activated carbon filters in the manhole inlets. There are differences in type and effectiveness depending on the technical approach. Lenz and his colleagues became knowledgeable early on.
“For necessary reasons, but also for testing, we purchased some colasi filters four years ago. We have had good experience with them.”
- Reiner Lenz
Mats with bio-organisms
For the current problem in the larger area around Karlsruher Strasse, a requirement of around 60 deployments has been calculated. It was not only because of the good filter effect that coasli was chosen again. Ulrich Bethge from the manufacturer explains what makes the system tick.
“The highlight is the natural microorganisms,” Bethge reveals. “They metabolize the most common odorants”. The cultures come from the company’s own laboratory. “They eat up the stench”. Thus, these filters work in a biological way, but not only exclusively: two other stages are built in that filter mechanically and chemically. The insert made of activated carbon is important. The porous, fine-pored carbon has a catalytic effect and thus neutralizes many odor components. “We achieve virtually complete odor retention with these filters”. The manufacturer calls its approach triple hybrid filtration. The process is also used in large-scale plants, such as for municipal sewage treatment plants or in industry.
“Preventive maintenance”
Lenz and his colleagues manage the installation in the sewer themselves. Around ten minutes are estimated for each piece. Changing the filter mats when they have reached their service life is even faster. “We expect service lives of up to three years,” says Bethge, referring to the individual operating conditions. The filters are not pathogenic to humans, plants or animals and are therefore harmless to health. Filter mats are easier to handle than tablets, for example, as in other systems. “On top of that, storage is easier,” adds Lenz.
The department also sees the filters as a contribution to cost savings. This is because, depending on the type, odorous substances can damage the sewer structure and technical systems in the long term. The cause of this is microbacterial induced corrosion (MIC) caused by hydrogen sulfide, which often requires expensive remediation. The filters thus not only act as odor killers, but also as a comparatively inexpensive preventive maintenance measure.
