Case Study: CH4 and N2O Monitoring at Stockholm WWTPs

Product catalog summary

Introduction
This document presents a case study by Fresenius Umwelttechnik on monitoring methane (CH₄) and nitrous oxide (N₂O) emissions at Stockholm's wastewater treatment plants (WWTPs). These plants are significant sources of greenhouse gases (GHGs), with methane and nitrous oxide having a much higher global warming potential than carbon dioxide (CO₂).

Background
Stockholm Vatten operates two major WWTPs serving 1.1 million people. The Henriksdal plant, one of the largest in the world, is built inside solid rock. Both plants use advanced biological nitrogen removal processes and are committed to full GHG transparency.

Measurement Challenge
The challenge involves continuous, high-precision monitoring of GHG emissions at multiple points. The Gas Analyzer 220 and 320 units are used for this purpose, offering specific measuring ranges and high accuracy for CH₄, CO₂, and N₂O.

Monitoring Equipment

Gas Analyzer 220: Configured for CH₄ and CO₂ with measuring ranges of 1–1,000 ppm and 1–10,000 ppm for CH₄, and 5–10,000 ppm for CO₂. Accuracy is less than 3% from the measured value.
Gas Analyzer 320: Configured for N₂O with a measuring range of 1–50 ppm, and for CH₄ and CO₂ with similar ranges as the 220 model. Accuracy is also less than 3% from the measured value.

Both analyzers are installed in robust cabinets with interference compensation and analogue output for SCADA data transfer.

On-Site Installation
At Henriksdal, wall-mounted cabinets are installed directly at sampling points. Sample lines are routed from process streams to analyzer inlets, and remote monitoring is integrated into Stockholm Vatten's SCADA system. All instruments were installed without unplanned downtime.

Fresenius Advantage
Fresenius offers reliable operation and service, continuous online measurement, fully automated systems, and low service costs. Their modern solutions replace estimated GHG data with continuous, verified measurements to help meet climate goals.

Catalog excerpts

Case Study: CH4 and N2O Monitoring at Stockholm WWTPs-1

A Case Study by Fresenius Umwelttechnik

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Wastewater treatment: A signi Global Warming Potential (GWP) of emitted gases over 100 years Carbon Dioxide

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Case Study: CH4 and N2O Monitoring at Stockholm WWTPs-3

Stockholm Vatten Benchmark Serving 1.1 million people across two major treatment plants Both plants operate advanced biological nitrogen removal (BNR) processes. Stockholm Vatten committed to full GHG transparency as part of its climate strategy. Henriksdal is one of the world's largest wastewater treatment plants built entirely inside solid rock. Henriksdal WWTP Bromma WWTP

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Continuous, multi-point monitoring at scale

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The Solution: Monitoring Equipment High-precision, continuous monitoring of greenhouse gas emissions at key measuring points. < 3% from measured value Installed into robust cabinets Accuracy: < 3% from measured value Interference compensation

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gured for Wastewater Treatment Measuring Ranges: Measuring Ranges: Accuracy: < 3 % from measured Accuracy: < 3 % from measured Cabinet Installation Seamless Integration 5 analyzers deployed in dedicated Equipped with built-in interference Includes analogue output 4–20

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gured for Wastewater Treatment Measuring Ranges: Measuring Ranges: Accuracy: < 3 % from measured Accuracy: < 3 % from measured Cabinet Installation Seamless Integration 2 analyzers deployed in dedicated Equipped with built-in interference Includes analogue output 4–20

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On-Site Installation Seamless Integration at Henriksdal Wall-mounted cabinets installed directly at each sampling point due to the vast size of the plant, ensuring proximity to the measurement locations. Sample lines routed directly from process streams to analyzer inlets. Green status LEDs and LCD displays enable local status checks without a laptop. Remote monitoring via 4–20 mA signals integrated into Stockholm Vatten's SCADA. All 7 instruments were installed and operational with zero unplanned

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Reliable operation Reliable service Continuous online measurement Strong pumps for long distances Fully automated systems Direct contact to support Modern solution from an Automated zero point correction (no test gas) innovative manufacturer

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