Clean drinking water is essential to life, and its importance cannot be stressed enough.
We are a regional water supply company owned by the city of Lahti
and we have been providing water supply services to Lahti residents for more than a hundred years.
Lahti Aqua Ltd is the parent company for the subsidiaries Aqua Service Ltd,
Aqua Network Ltd and Labio Ltd with a 60% ownership.
Our primary task is to ensure that the water services in our area are high quality, safe and cost-effective.
Our water services include top-quality customer service operations, sourcing and distributing water,
wastewater management and treatment as well as the maintenance, servicing and development of the aforementioned functions.
Our customer service team takes care of invoicing our customers and helping builders with new connections.
Our administrative team is responsible for the financial, IT and HR operations of the entire Lahti Aqua Group.
We operate water supply services for 145,000 people and companies in Lahti and Hollola.
We also started to supply water to Pennala in Orimattila in 2020, after concluding a trans-border sales agreement with Orimattilan Vesi.
We supply our customers with groundwater only, which is quite unique in urban conditions.
Our highly-skilled staff members ensure that the quality of the groundwater remains first-class, from the water intake plant to the customer’s tap.
We are also responsible for treating wastewater in as eco-friendly manner as possible and for returning the treated water back to the environment.
Welcome to this tour to see how all this is done.
All the water we use is groundwater.
Groundwater is formed when rainwater filters through layers of soil.
The groundwater areas in Lahti are mainly located on the Salpausselkä terminal moraine formation and on the surrounding ridges.
The soil of the Salpausselkä terminal moraine formation is ideal for filtering rainwater,
and our area of operations yields 100,000 cubic metres of groundwater every day,
which is enough to fill more than 40 Olympic-size swimming pools.
The Salpausselkä terminal moraine formations were formed approximately 12,000 years ago
during the previous ice age as the glacier stopped melting due to global cooling.
The eskers were formed from the sand and gravel layered in the meltwater tunnels in the continental glacier.
The water is cleaned of bacteria and contaminants when filtered through layers of soil,
so soil has a significant impact on the water quality.
Layers with complex structures of different soil types were formed on the south side of the Salpausselkä ridge system.
This ensures that Salpausselkä is an excellent place for collecting groundwater even today.
Groundwater can be found almost everywhere in soil.
However, we only classify as groundwater areas those areas where water is easy for society to access due to the composition of the soil types.
A water table, or the surface of groundwater, is the level below which all porous space in the soil and bedrock is filled with water.
In the Lahti area, the distance from the groundwater surface to the surface of the earth varies from about two metres to up to 50 metres.
Groundwater protection is particularly important in Lahti and Hollola
as residential and industrial areas are mainly located on top of their drinking water resources.
Once polluted, groundwater purification and remediation take a long time.
In groundwater areas, risky activities include washing cars, old oil drums, geothermal wells and fuel stations.
Groundwater areas have a wide range of restrictions on land use and human activities that aim to prevent the groundwater from being polluted.
Groundwater areas and groundwater intake protection zones are often marked with signs.
If there is an accident or damage, it is important to limit the damage
and notify the emergency services and the municipal environmental protection authority without delay.
A total of 20 water intake plants are in use in our area of operations.
In these, groundwater is pumped from the soil from wells 10-15 metres deep, called strainer wells.
The sites where groundwater is pumped have been carefully selected
after groundwater and soil testing has shown them to have excellent water quality and quantity.
It is also important to protect the surrounding areas of the water intake plans
to prevent contaminants from entering the wells.
The eskers are such effective filters that the rainwater and meltwater they purify would be drinkable as such,
and the water requires only a little treatment before it is transferred into the network.
The staff in the water production process ensure that the water supplied is of a uniformquality
and that the pumps and chemical equipment are in good condition at the water production plants
to guarantee operational reliability.
Depending on the area, the natural pH in groundwater is in the range of 6-7.
The treatment increases the pH of the water closer to 8
so that its corrosive and aggressive effect on the supply network is reduced.
The pH level of the water is raised using caustic soda or limestone.
Groundwater is also disinfected using UV light.
UV light kills viruses, bacteria and other microbes in raw water, but does not otherwise alter its chemical composition.
Before the water is pumped into the network, a small amount of chlorine in the form of chloramine is added to it.
This ensures that the water is clean when it reaches the end user.
Not all the water pumped at water intake plants is used immediately.
Some of it is stored in water towers.
Water towers also equalise the water pressure and act as storage in the event of fault situations.
There are six water towers in our area of operations,
and water is pumped in at night ahead of the morning’s peak usage.
Water quality is constantly monitored by samples,
which are taken from groundwater, water intake plants, the network and water tanks.
Our highly-skilled employees take about a thousand water samples every year.
They are also taken by an external certified sampler.
In order for water to be supplied to all residents and companies in our area of operations,
the water distribution network must reach even the most remote users.
The length of the water supply network in our area of operations is approximately 1,200 kilometres.
About 70 control and monitoring stations are also needed
to provide information on water consumption in different parts of the city.
Due to the hilly terrain in the Lahti region, water has to be pumped in the network.
This ensures sufficient pressure in the network.
The pressure may also need to be reduced to make sure that there is not too much pressure in the low-lying areas of the network.
Monitoring the condition of the water supply network is a demanding job because the network is invisible underground.
Leaking water pipes can be detected quickly thanks to the monitoring and active use of the network.
It saves energy and water when leaks are repaired without delay.
The water supply network becomes visible when the pipes hidden under the streets are excavated for repairs.
Repairing the old network and building new networks are part of our systematic activities.
Our experts in the design and construction team are responsible for the planning and construction of new water supply projects
and ensure that the networks that require repairs due to their age are repaired on schedule.
We are also responsible for treating wastewater in as eco-friendly manner as possible
and for returning the treated water back to the environment.
Our area of operations has more than 1,000 km of wastewater sewers
which take wastewater from domestic and industrial sewers to be treated at wastewater treatment facilities.
Some of the wastewater flows by gravity
and some has to be pumped along the sewer network due to differences in levels.
There are almost 300 sewage pumping stations in our area of operations.
There is a wide range of tasks involved in the running of the sewage disposal system
and the integrated operations of sewage pumping stations.
More than ten water service professionals take care of any disruptions in the sewer network,
run maintenance and testing activities as well as look after the functioning of the sewage pumping stations.
The operations at sewage pumping stations are monitored around the clock using an automated system.
Like the water supply network, the sewer network and sewage pumping stations are regularly inspected and maintained
using measuring devices so that possible overflows can be taken care of as soon as possible.
Preventive maintenance measures and repairs ensure minimal leakage
so that no leaking water enters the wastewater treatment plants.
This also significantly reduces energy consumption and the amount of chemicals used in the wastewater treatment plants.
Sewer networks located in groundwater areas and in the vicinity of water bodies are especially closely monitored.
We have developed measures to detect substances that should not be in the sewer system such as oils and other hazardous substances.
This job is facilitated by sensors placed in the network.
When hazardous substances are detected as quickly as possible, it is possible to avoid having to make repairs in the network
and to guarantee the normal operation of wastewater treatment plants.
Wastewater treatment began in Lahti in 1910, and wastewater treatment is subject to an environmental permit.
Our area of operations has four wastewater treatment plants,
which are located in Kariniemi, Ali-Juhakkala, Nastola and Hämeenkoski.
We treat approximately 90% of the wastewater in our area of operations
at the two largest wastewater treatment plants, Kariniemi and Ali-Juhakkala.
Modern wastewater treatment plants are energy-efficient and suitable for urban environments.
The wastewater treatment process is continuous and goes on non-stop every day.
Wastewater is treated mechanically, biologically and chemically at the wastewater treatment plants.
The wastewater circulates at the treatment plant for an average of one day before it enters the Nikula equalisation tanks.
There it stays for about two days, after which it is further disinfected with ultraviolet lights before it enters the river Porvoonjoki.
The process teams at the wastewater treatment plants are responsible for controlling the treatment process in accordance with the permit conditions.
The process is monitored and controlled around the clock using an automated system.
The process teams are also responsible for the preventive maintenanceand servicing of measuring devices and equipment.
The cleaning process starts with the mechanical phase,
in which coarse solids are removed from the wastewater by screening.
Sand, gravel, fat and other mixed waste are then removed from the wastewater.
In wastewater treatment plants, mixed waste is called screenings.
It is important to remove sand and screenings at the start of the wastewater treatment process
to prevent them from damaging the equipment and causing harm to the treatment plant.
The treatment plant also receives wastewater from sparsely populated areas, i.e. septic tank sludge, to go through the mechanical phase.
Phosphorus is chemically removed from the wastewater after the mechanical treatment process.
Iron salt, i.e. ferrous sulphate, is added to the wastewater, which precipitates phosphorus from the water in separable form.
The precipitated phosphorus settles on the bottom of the sedimentation tanks as part of the wastewater sludge, which is led to further treatment.
The treatment can remove more than 98% of the phosphorus in the wastewater.
The pH value of the wastewater is also adjusted if necessary, and this is done using soda or caustic soda in our treatment plants.
The biological treatment of the wastewater involves using the bacteria contained in the wastewater.
The biological phase takes place in aeration tanks at the wastewater treatment plants.
There is a lot going on in the large tanks although nothing much is visible.
The aim is to create optimal conditions for bacteria to grow and reproduce
so that they form activated sludge, which consumes organic matter from the wastewater.
More than 70% of the nitrogen in the wastewater is removed as a result of the bacterial growth and activity.
In the final sedimentation phase, some of the activated sludge is returned to the aeration tanks to continue the process.
More than 98% of organic matter is removed from the wastewater in the biological treatment.
As a final step in the process, the effluent is disinfected efficiently to a level that meets the requirements of the Bathing Water Directive.
This is done by disinfecting the outgoing water with ultraviolet light.
The UV unit is on during the bathing season.
Wastewater sludge refers to the settleable solids generated in the wastewater treatment process.
Nothing is thrown away, but the sludge is used to produce heat, electricity and in growing media as part of the sludge treatment process.
The aim of the treatment is to reduce the volume of the sludge as much as possible by removing excess water.
In the first phase, sewage sludge is dewatered using mechanical drum thickeners.
The process uses polymers as an auxiliary chemical, which makes the dewatering process more efficient.
The thickened sludge is led to methane tanks to digest.
During the digestion process, the organic matter in the wastewater sludge is broken down under anaerobic conditions.
Biogas, or methane, is generated during this process.
Biogas is used to produce heat by burning it in gas boilers at the wastewater treatment plants in Lahti.
The heat generated is used for heating the treatment plant buildings and the business premises,
and any surplus heat is sold to Lahti Energia’s district heating network.
After the digestion process, the sludge is further treated with centrifuges, which mechanically separate water from the sludge.
The dewatering process is enhanced by the use of polymers.
Several days a week, the centrifuged sludge is transported to our subsidiary Labio’s composting plant for further processing.
The composting of dried sludge and organic waste produces compost, which is used in building green spaces.
Wastewater treatment plants are monitored around the clock using an automated system.
In addition to automated testing, samples from the various phases of the wastewater treatment process are taken daily for analysis at our process laboratory.
Every week, 90 samples are also taken from the wastewater treatment plants, and more than 100 analyses are carried out on these samples.
Samples are taken both from the wastewater and sewage sludge.
The biological and chemical quality of the wastewater and the amount of nutrients it contains are studied.
The properties of the sludge are studied at the different phases of the treatment, such as the volume of dry matter in the sludge.
The wastewater treatment process is monitored and controlled on the basis of the results of these in-house analyses.
Harmful and hazardous substances are also monitored in the treated wastewater and the receiving body of water.
In addition to our in-house monitoring
official samples are also taken from the treatment plants
for an external accredited laboratory in accordance with the environmental permit.
A well-managed wastewater treatment process is the most impactful measure to protect the environment.
It has positive effects on the safety of the environment, the condition of waterways,
the water cycle, sustainable development and circular economy.
The water leaving the Ali-Juhakkala, Kariniemi and Nastola treatment plants is discharged into the river Porvoonjoki,
which flows into the Baltic Sea.
It is our responsibility to ensure that the river Porvoonjoki has sufficient flow and oxygen content.
We care about the people and the environment in our area of operations.
We are present in our customers’ lives every day.
We would like to increase our customers' awareness of the use of water
and to offer guidance and instructions in all matters related to water supply if necessary.
Lahti and the surrounding areas produce more water than we consume here.
There is enough water and our customers can enjoy it without worrying.