Getting to the Bottom of the Matter
Drainage sewers must be cleared of grit and sludge so that wastewater and stormwater can flow through freely. We use state-of-the-art technology for this purpose, as most sewers are so small that they cannot be accessed
Smaller sewers can be cleaned using simple water cleaning or high-pressure cleaning. A special cleaning apparatus is used, which is pulled through the sewer with the help of a cable winch. Sludge, sand and other deposits are then transported to the next manhole where they are suctioned up.
Pumps on our special vehicles, used for high-pressure cleaning, can generate water pressure of up to 150 bar with their pumps. This pressure is 30 times higher than the pressure in the water pipeline network. The pressure loosens deposits, swirls them up and flushes them to the next manhole, where they are suctioned up.
In most of the sewer cleaning vehicles, the high-pressure cleaning is combined with sludge suction equipment. Water sucked up with the sludge is simultaneously filtered and used again to flush the system. Sewers at a height of 1.20 metres are accessed for cleaning. Some of the deposits have to be shovelled away because they cannot be removed by scrapers. Sewer operations employees also work underground to manually clean special structures such as stormwater tanks and coarse filtering equipment in the storm-water sewer network. Siphons (i.e. sewer underpasses below other installations, such as the underground railway) are cleaned by high-pressure cleaning.
Cleaning and Inspection
Wastewater sewers can collapse or leak if they are penetrated by tree roots. Wastewater then leaches into the soil and can contaminate groundwater. Conversely, percolating groundwater that seeps into the pipes can increase the overall load at local sewage treatment plants. Due to the high level of groundwater, this is a common occurrence in Berlin. Repairing damage in the sewer network effectively serves to protect the environment. Therefore, wastewater sewers need to be inspected on a continuous basis. Most accessible sewers can be physically inspected by employees of the sewer operations service centres. The nonaccessible sewers are inspected using mobile sewer cameras. Even building connection sewers, which are only 15 centimetres in diameter, can easily be examined this way.
Strict Requirements for Trade and Industry
Our laboratories at Berliner Wasserbetriebe continually check the effluents of the sewage treatment plants in order to be able to make any adjustments to the treatment processes at any given time based on the quality of the effluent. The sewage treatment plant is managed on the basis of the measurement values obtained from constant sampling.
Any effluents coming from industry and trade customers are tested by Berliner Wasserbetriebe's Discharge Monitoring department. Around 20,000 companies are registered with our organisation, and 1,200 of them are monitored routinely. It is strictly prohibited by law to discharge substances that are hazardous to water into sewers. In addition to this regulation for industrial and trade customers, the German “Indirect Discharge Ordinance” clearly states that contamination is to be identified at the point where it first occurs.
These legal requirements are there to safeguard people who have to work in the sewers, pumping stations and other drainage facilities. In addition to this, the drainage facilities may not be damaged and the biological processes may not be disturbed during wastewater treatment. For example, cyanide, chlorinated hydrocarbons, heavy metals or acids could potentially cause major damage.
The basis for the investigations of the individual stages of wastewater treatment include, for example, a permit from the water authority and quality-based ordinances; compliance with these is ensured through unannounced spotchecks by the state water authority.