We Protect Our Water!

We protect our water! CLEAN WAT ER FROM YOU TO THE SEA 1 The next generation s water 2 CONTENTS THIS IS SYVAB Our plant and its purpose ............................................4 FROM DIRTY WATER TO CLEAN Here’s how ......................................................................................6 THE TUNNEL SYSTEM FAQs about the tunnels ................................................10 VISIT SYVAB Syvab loves having visitors .......................................12 UPGRADE Higher demands on the treatment plant 14 BIOGAS How we make fossil-free vehicle fuel ............16 BIOSOLIDS An important end product ........................................18 DID YOU KNOW? Fun facts .......................................................................................20 JOBS AT SYVAB A meaningful job .................................................................22 TIPS Little things that make a difference ...............24 RESEARCH AND DEVELOPMENT Research projects at Syvab.....................................26 40+ YEARS OF TREATING WATER Read about Syvab’s history .....................................28 FOR KIDS Simple guide to wastewater treatment....30 We protect our water! Syvab Himmerfjärdsverket, SE 147 92 Grödinge | +46 8 410 776 00 | [email protected] | www.syvab.se Production: Roxx Communication Group, www.roxx.se. Project Manager: Daniel Abenius. Text: Roxx and Syvab. Photo: iStockphoto, Jennifer Glans, Syvab’s own images. Graphic design & layout: Malin Svensson. Print: Åtta.45 2018 3 Sludge silo Gas holder Sludge thickener Sludge treatment Bio reactors Gas compressor station This is Administration Electrical & ventilation building Syvab M Primary The southwest Stockholm region's wastewater screening treatment company – SYVAB (known as Syvab) plant – owns and operates the Himmerfjärden waste water treatment plant, Sweden's fifth largest. The plant is located in Grödinge, in the southern part Upgrading plant of Botkyrka municipality. The wastewater treatment plants task External infrastructure is to receive and treat wastewater from The water reaches the plant through the more than 350,000 people in house- 55-kilometre tunnel system, which is holds, companies, schools, industries etc. owned by Syvab (see the tunnel system tanks, which means we are able to treat The water arrives at the plant through a illustration to the right). There are two any surface water mechanically in the 55-kilometre tunnel system that is con- pumping stations that pump water from event of power disruptions or abnormally nected to the municipalities of Botkyrka, the connected municipalities (previously high flows. Water is pumped from the Nykvarn, Salem, Södertälje, south Stock- mentioned) and in to the plant. There Pilkrog pumping station in Järna directly holm and parts of Huddinge. Every day it are measuring stations at the connection to the treatment plant via an underwater receives around 120,000 m3 of water for points so that each municipality is in- pressure line. All of Syvab's pumping treatment. It takes around 20 hours for voiced according to its share of the treat- stations are also equipped to handle com- the water to pass through all of the treatment plant's load. The Eolshäll pumping prehensive water ingress. When water is ment steps before it can be released into station in Hägersten transfers the water flushed away, it takes on average 8 to 10 the Baltic Sea. You can read more about from southwest Stockholm to the main hours before it reaches the wastewater how we do this on pages 6 to 9. tunnel. This station has sedimentation treatment plant. 4 The tunnel system Eolshäll Skärholmen Mälarhöjden Segeltorp Slagsta Östertälje Tullinge Södertälje Salem Rönninge Hamra Tumba Nykvarn Vårsta Tunnel Järna Pressure line Himmerärden wastewater Pumping station Pilkrog treatment plant Skanssundet The tunnel system and its two pumping stations move the water from the connected municipalities to the treatment plant. Read more about the tunnels on pages 10-11. Methanol tank Sludge liquor treatment Presedimentation ILLUSTRATION: PETTER LÖNEGÅRD PETTER ILLUSTRATION: M Fluidised bed B Aeration tanks B F Intermediate sedimentation Disc filter B Post sedimentation B Water outflow Direction of the water M Mechanical treatment B Biological treatment F Filtration 5 HERE’S HOW we treat the water INLET AND MECHANICAL TREATMENT Inlet doms and rags that unfortunately arrive the phosphorus dissolved in the waste to Where the main tunnel discharges into the with the wastewater. Read more about become a solid that can be separated later. treatment plant 54 metres underground what may or may not be flushed away on there are sluice gates that protect the plant page 24. The solids are ground so that Main pumping station from extreme flows. The tunnel has such they do not plug up the treatment plant's With the aid of large pumps, the waste- a large volume that it can store the water pumps; they are separated from the wastewater is then pumped up to the surface from five days' normal flow if a major power water at a later treatment stage. As a back- for further treatment. There are six pumps cut or similar should occur. up to the wastewater grinder there is a bar in all, and the number in operation de- screen with a 20 mm bar gap. The solids pends on the size of the flow to the treat- Wastewater grinder and coarse screen separated by the screen are compacted and ment plant. The average flow from the The first stage in the treatment process is a sent for incineration. A precipitant is added pumping station under normal conditions grinder for solids such as tampons, con- downstream of the grinder. This causes is 1,400 l/s. Screen room Main pumping station 6 HERE’S HOW Fine screens Grit washers Sand washer Primary screening – consisting of fine burned to provide district heating. Follow- The particles that sink are scraped away screens, grit washers, sand traps and ing the fine screen, the water is cleaned in by means of scrapers along the bottom and sand washers a sand trap. In all, there are three parallel are then transferred to a sand washer. In Once up at ground level, the wastewater tanks, each 30 metres long, and this is the sand washer, the organic material is first passes a fine screen with 6 mm holes. where the heavier particles such as gravel washed away and returned to the waste- Here, the screenings that were crushed in and sand are separated from the water. water. The sand and the gravel are then so the inlet are separated. The separated sol- This is done by blowing precisely the right clean that they may be used again. After ids are transferred to a grit washer before amount of air through the water, so that primary screening, the water is led to the being led to a container that is transported the light particles stay in suspension while pre-sedimentation process. to a refuse incineration plant where it is the heavier particles sink to the bottom. Primary screening was taken into operation at the end of 2016. The new, clean, working environment is much appreciated by the employees. 7 sludge consists of bacteria that "eat" the dissolved oxygen-consuming material and convert the nitrogen in the water. The bacteria convert the nitrogen from ammonium (NH4) to nitrate (NO3), a process called nitrification. In other words, no nitrogen purification takes place in this step; in- stead, the nitrogen is merely converted into a new form. The micro-organisms are aero- bic, i.e. they need oxygen to breathe and for Presedimentation tanks this reason air is added all day round from nozzles located on the bottom of the tanks. Pre-sedimentation To prevent the activated sludge from being Intermediate and postsedimentation tanks » Pre-sedimentation is the final step in the flushed out of the system, the aeration mechanical purification process and com- tanks are followed by sedimentation tanks. prises the first section of the large tank Post sedimentation block. The tank block is located outdoors Intermediate sedimentation The micro-organisms that did not sink in and, between the various treatment steps, After aeration, the micro-organisms are the intermediate sedimentation process there are machine rooms for electricity, separated from the purified water by two sink in secondary sedimentation. Since it automatic control devices and pumping sedimentation steps, intermediate and is important to have bacteria with good equipment. post-sedimentation. The sludge is allowed sedimentation properties in the system, In all, pre-sedimentation consists of to sink to the bottom and is scraped into the bacteria that sink in the secondary 16 parallel tanks, each 50 metres long. a sludge hopper, from where it is pumped sedimentation are not wanted. The sludge Because the environment has little turbu- back to the aeration process. In this way, is scraped into a sludge hopper, from where lence here and the heavier particles have the micro-organisms are reused and can all the sludge is removed from the process the chance to sink to the bottom, they are do their job several more times. As the and pumped to the flotation plant. The separated from the water. The material micro-organisms reproduce and increase in water is led from secondary sedimentation that sinks to the bottom is called primary number, some of the biosludge is taken from to the fluidised bed, which is the last step sludge; it is removed by means of scrapers, the system and moved to the flotation plant. in the biological purification process. transferred to a sludge hopper and pumped away for sludge treatment. Fluidised bed, denitrification The fluidised bed is the final stage in the BIOLOGICAL PURIFICATION removal of biological nitrogen. This is Aeration, nitrification where micro-organisms transform the Following pre-sedimentation, the water is nitrate (NO3) formed in the aeration tank led to the biological purification process, into nitrogen (N2) in a process known as the main task of which is to remove the denitrification. The micro-organisms grow dissolved nitrogen and oxygen consuming as a biofilm on billions of small grains of material from the water.

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