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WASTEWATER TREATMENT IN LAHTI

WASTEWATER TREATMENT IN LAHTI. There are 2 wastewater treatment plants in Lahti - Kariniemi - Ali-Juhakkala In these slides we examine waste water treatment in Kariniemi, where the daily intake was 21 500 m3 ( 2011). WASTEWATER TREATMENT IN LAHTI (Kariniemi).

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WASTEWATER TREATMENT IN LAHTI

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  1. WASTEWATER TREATMENTIN LAHTI • Thereare 2 wastewatertreatmentplants in Lahti - Kariniemi - Ali-Juhakkala • In theseslidesweexaminewastewatertreatment in Kariniemi, where the daily intakewas 21 500 m3 (2011)

  2. WASTEWATER TREATMENTIN LAHTI (Kariniemi) WWTP was built in 1975 Biological treatment – activated sludge process WWTP is underground in a cave (volume = 120 000 m3) Sludge treatment on the ground Operation of the WWTP happens from control room

  3. SCREENING • Screeningremoves big particles (e.g. paper) fromwastewater. • Screeningsarewashed, dryed and transported to a landfill.

  4. GRIT REMOVAL • Grit is removedbysedimentation, whichmeansseparation of solid, insoluable, particles into a concentratedslurry. • Grit is washed, dryed and transported to a landfill.

  5. PRIMARY CLARIFICATION • In primaryclarificationsludge is removedbysedimentation. • Settledsludge is pumped to a sludgetreatment. • Effluentgoes to the aeration (biologicaltreatment).

  6. AERATION • Aeration + secondarysedimentation = biologicaltreatment • In aeration, the activatedsludgeconcentration is 3 g/l. • Alltogetherabout 35000 kg of bacteria.

  7. SECONDARY CLARIFICATION • In secondaryclarification the activatedsludgesinksdown and is pumpedback to aeration. • Effluentgoes to the Nikula basin via tunnel, fromwhich to river Porvoonjoki.

  8. NIKULA BASIN • Volume of the basin is 50 000 – 60 000 m3

  9. PROCESS RECAP WATER TREATMENT • Screenings • Gritremoval • Primarysedimentation • Aeration • Secondarysedimentation • Tunnel • Nikula basin • Porvoonjoki SLUDGE TREATMENT • Thickening • Anaerobicdigestion • Sludgedryedwithcentrifuges • Composting

  10. PROCESS RECAP BIOGAS • Biogas is collected and used to heatwastewatertreatmentplant. • The surplusgas is sold to powercompany. CAVE VENTILATION • Cave is ventilatedbytwoblowers -> 20 m3 / second • Air is changedonce per hour in the cave.

  11. THAT’S ALL FOLKS THANK YOU

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