Tampere’s Water System
Tampere’s Water History
From 1835 to 1921, just after the industrial revolution,
In the early 1900s,
It seems like Tampere is unusual with such a water centered history, but you'd be surprised. Do you know where your water comes from? Do you know why your city was founded where it is?
Warning: the following section contains more science than usual!
Artificial Groundwater Recharge (AGR)
Reija, one of my collegues at the lab, is focusing on AGR for her PhD work. The main idea of AGR is to load up aquifers with untreated water. The natural microbial processes in groundwater are capable of removing certain contaminants that are currently removed at the treatment plant. Her results may help the City of
She has two sets of reactors installed at the local water treatment plant. She varies temperature and oxygen with time in one set. Some people worry that the CO32- in the system will turn to organic matter instead of CO2 and cause the AGR system to clog and shut down. She has some smaller fluidized bed reactors that provide a small, but perfectly porous material to simulate ideal aquifer conditions. In the fluidized bed reactors, Reija studies the effects of varying the hydraulic retention time, fluidization rate, temperature, and phosphorus and nitrogen concentrations on the microbial communities. She’s currently using stable carbon isotopes to measure the biodegradation rate. She’s getting approximately 30 to 50% biodegredation, based on the 12C:13C ratio.
The present-day treatment plant was built in the end of the 1970s and is located in Rusko, approximately 2 km from the Tampere University of Technology (TUT). It’s time for a renovation, but there is a hot political debate over whether to switch to artificial groundwater recharge (AGR) that is holding up plans for renovation. AGR is (not coincidentally) also a hot research topic in our lab at TUT. The city doesn’t want to renovate or build a new treatment plant if it is going to switch to AGR, which requires much less water treatment. AGR consists of pumping surface (or whatever type of) water into the ground and letting the microbes in the soil do the treatment. It would still require chlorination, but almost entirely eliminates the need for a water treatment plant. However, we need some science to tell us if it’s a viable option for
The current treatment plant consists of 720 km of pipelines and five steps of treatment, with a flow rate of 1800 to 2200 m3/hr. These are the five treatment steps:
- Calcium carbonate addition. This prevents corrosion
- Hypochlorite addition. This prevents biofilm from forming on the sand filters.
- It may also unfortunately cause disinfection byproducts to form, which cause cancer in lab animals at high doses
- Rapid sand filtration. There is a one meter deep sand bed that is backwashed once per day. This process removes natural organic matter and iron. Some people think the rapid sand filtration should go before the hypochlorite addition to reduce the formation of disinfection byproducts.
- Air flotation. This treatment process is considered advanced and efficient. Ferric sulfide sticks to the organic matter and forms flocs. These flocs adhere to bubbles that are diffused through the water column, bringing the organic matter to surface where it can be scraped off.
- Activated carbon filtration. Water is filtered, the pH is raised to 8.5, and the final chlorination takes place before the treated water is stored in one of
’s five water towers. Tampere
So wow! Before I drink that water, it sure goes through a lot! It's pretty nice that we don't get Typhoid here anymore. That's not the case everywhere!
By the way, there’s a new policy to keep the door shut at the water treatment plant in Rusko. Since you need an appointment to get into our water treatment plants in
**Näsijärvi is nowhere near the largest lake in Finland, that was a mistake (see Sannamari's comment)!