Bacteria are a natural part of the water: purified drinking water contains about 20’000 to 300’000 bacterial cells per milliliter. Increasing water demand and deteriorating natural water quality are a constant concern, particularly for the water treatment industry. Selective laboratory measurements are intermittent and are no longer sufficient to current quality standards. Permanent water monitoring has become a necessity.

Measurement systems and sensors for continuous on site monitoring have become increasingly important and already represent the state of technology for many water providers. These online measurements systems cover physical, optical and chemical parameters such as temperature, flow, pressure, conductivity, turbidity (NTU), pH, monochloramine, fluorine compounds and nitrates.

Missing so far was a reliable on site measurement that captures bacterial activity of the water within short intervals and records the general and hygienic microbiological state.

Online Bacteria Analyzer

The Online Bacteria Analyzer is the first autonomous measurement device that meets the complex requirements for the use along the entire water production and distribution chain. All required preparation steps have been integrated into a single, process suited device which provides measured data and results online.

It is designed for continuous operation, 24 hours a day, 7 days a week. The device measures without human intervention for at least two weeks, then consumables like sheath fluid, pure water and stain have to be replaced. OBA’s fail-safe system handles occurring interferences and compensates them.

Flow Cytometry

By staining water samples with DNA dyes, the flow cytometry technology can differentiate between organic cells and DNA-free, inorganic particles. SYBR green induces a green fluorescence on DNA or RNA. Propidium Iodide can permeate the damaged membrane of dead cells, but cannot permeate those of intact and living cells.
The stained cells and particles are then streamed through a glass capillary where they are illuminated by a focused laser beam. The scattered light of cells/particles and the emitted fluorescence of the dye are then collected through appropriate detectors.

OBA’s detection is based on this flow cytometry technology. The device distinguishes itself due to its optical design, the high sampling rate of the optical sensor with 2 MS/s or 4 MS/s and the 24 bit dynamic range of its signal converters. Due to the OBA SmartDetect™ detection algorithm it is no longer necessary to define a traditional signal threshold. OBA is immune to zero point offsets, caused by varying samples.

Measurement Results

Individual water samples differentiate by their microbiological structure. After the measurement of a sample the results of two of the different scatter and fluorescence detectors can be combined to so called dot-plots.

By defining regions inside the dot-plots (gating) Information about specific cell types can be retrieved like the total cell count (TCC), the amount of LNA (low nucleic acid cells) and HNA (high nucleic acid cells) and alive and dead cells.

Traditional methods at laboratories to determine the bacteria that form colonies of heterotrophic bacteria (HPC or heterotrophic plate count) take up to 48 or 72 hours until there are results. OBA reduces measurement time significantly: precise, real and high resolution results on the microbial state of the water are available within minutes.


OBA online monitoring is based on comparing the results of two or more consecutive measurements. Measuring the same sample source under constant conditions will result in minor deviations only. In case of a real event, such as an infiltration by rain water, contamination by manure or a malfunction within the treatment process the results inside the scatter and fluorescence plots will change immediately.

By exceeding predefined thresholds a warning or alarm will be triggered: acoustic, optical, by email, by output signals to a logic controller (PLC) and by ethernet (Modbus/TCP). One can respond quickly to microbiological events.


The Online Bacteria Analyzer has a powerful and comprehensive control and analysis software, focusing on the ease of use without limiting possibilities for the user. Flexibility was and is considered as important Feature. By using predefined Templates one can start using the OBA in no time. The software application offers a wide variety of usage; Ranging from a basic user to start a single measurement or measurement-sequences to the power user that parametrizes sample preparations and measurements or defines detailed processes and sequences.

Furthermore the software application includes an extensive analysis toolset to evaluate data by given criteria after each measurement.

The integrated database guaranties save data handling and backup. By using the OBA Data Analyzer application data can be access remotely and then processed in a desktop environment.


  • Measurement results within 15 minutes
  • Closes a gap in online monitoring
  • Online operation on site where monitoring is required
  • Operates at least two weeks without intervention
  • Detection of non-culturable organisms possible
  • Automatic detection of alive and damaged (dead) cells
  • Early detection of malfunctions, defects or external influences
  • Maximum security; 24 hours, 7 days a week
  • Designed for the use in process and industrial environment
  • Two sample ports, one single-port for individual measurements
  • Precise detection through OBA SmartDetect™ algorithm

Fields of Application

Drinking Water

  • Water suppliers
  • Quality control laboratories
  • Research
  • Food and beverage industry
  • Hospitals

Process Water:
Ultrapure and High Purity Water

  • Pharmaceutical and chemical industry
  • Food industry
  • Cosmetic industry
  • Electroplating
  • Semiconductor industry



Biological Contamination
of Drinking Water by Sabotage

  • Airports, water tanks of passenger aircrafts
  • Government buildings
  • Convention centres
  • Fairgrounds
  • Major events, state meetings
  • Potentially endangered objects