Monitoring bacteria in drinking water

Transcription

1 Monitoring bacteria in drinking water Application of the GRUNDFOS BACMON monitoring system Danish Water Forum Copenhagen, Jan. 28, 2016 Loren Ramsay, Ditte Andreasen Søborg, Torben Lund Skovhus: VIA Engineering Bo Højris, Mathis Dahlqvist, Lars Spicker Olesen: Grundfos Særlig tak til Tammes Lund Jepsen: Aarhus Vand Gør tanke til handling VIA University College

2 Time scale: from event to tap Minutes Hours Days Weeks Months Years Decades Contamination with natural parameters Contamination with major anions Spill or leak to groundwater Bacterial contamination

3 Instrumentation requirements Frequent sampling Fast analysis Low maintenance Automation At-line/ on-line

4 GRUNDFOS BACMON Fulfills the requirements on previous slide: Frequent sampling ( 12 min.) Fast analysis (< sampling frequency) Fully automatic At-line Low maintenance (few minutes every 1-3 months at low temperatures)

5 How does BACMON work? Uses pipe pressure or internal pump to flush system. Requires electricity and a drain for water discharge. 6 µl flow cell in which sample is sealed in a loop (1 particle/sample = 160 particles/ml) LED light source/moving lens/cmos-based image aquisition Image analysis software

6 Stored data 1. Main parameters Bacteria Non-bacteria 2. Control parameters Temperature (can indicate clogged flow cell) Pressure (can indicate clogged flow cell) Fouling (can indicate dirty flow cell) Bad volume (can indicate air bubbles) 3. Additional parameters (not user available) Equivalent-sphere size distribution (20 bins) Eccentricity distribution (20 bins) Others

7 Drinking water applications 1. Enables vastly improved water security through early warning against major contamination events (when a contingency plan has been prepared). 2. Provides data for improving & understanding operational practices (much like a turbidity meter). 3. May improve location of contamination sources in a DWDS (if there are many monitoring stations). 4. May ease the commissioning of new pipelines. 5. May provide information about biostability of drinking water. 6. Others applications (i.e. drinking water in warm climates, wastewater, food production)

8 Number pr. ml Effect of filter backwash Jan 5-Jan 6-Jan 7-Jan 8-Jan 9-Jan 10-Jan 11-Jan 12-Jan 13-Jan 14-Jan 15-Jan 16-Jan Bacteria Non-bacteria BACMON location: after cleanwater tank at Beder waterworks near Aarhus

9 Number pr. ml Recirculation after backwash jan 05-jan 06-jan 07-jan 08-jan 09-jan 10-jan 11-jan 12-jan 13-jan 14-jan 15-jan 16-jan NonBacteriaConcentration BacteriaConcentration BACMON location: before clean water tank at Truelsbjerg waterworks near Aarhus

10 Start of submersible pumps Start of pump in well backwash BACMON location: before clean water tank at Aquatarium waterworks near Aarhus

11 Truelsbjerg filter start-up Ammonium removal complete Operational problems with O 2 New waterworks started July 2, 2014 BACMON location: before clean water tank at Truelsbjerg Waterworks near Aarhus

12 Pipeline at water tower BACMON location: pipeline at Observatory water tower near Aarhus (water in and out)

13 Pipeline at water tower BACMON location: pipeline at Observatory water tower near Aarhus (water in and out)

14 Bacteria/particles-ratio Bacteria/total particles-ratio Indicator: bacteria/particle-ratio backwash water pigeon droppings 0,7 0,6 little spike 0,7 0,6 little spike medium spike 0,5 0,4 0,3 0,2 0,1 tap water big spike 0,5 0,4 0,3 tap water 0,2 0,1 big spike 0, : : : : :00 0, : : : : : : : : :00 BACMON location: 600L pallet tank at VIA Engineering, Campus Horsens

15 Aftergrowth in stagnant water BACMON location: 600L pallet tank at VIA Engineering, Campus Horsens

16 Bacteria size distribution BACMON location: after cleanwater tank, Beder Waterworks near Aarhus

17 Future perspectives 1. Combine with SCADA data so the alarm ignores spikes due to backwash (easily implementated). 2. Further experience in which real-life scenarios are most challenging for distinguishing bacteria from non-bacteria. 3. Further experience in using shape and size information proactively - smaller pixels may be necessary. 4. Consider designing a smaller device for easy placement in DWDS monitoring stations. 5. Consider a larger sample volume or pre-concentration for applications with low/inhomogenous concentrations.

18 Conclusions GRUNDFOS BACMON has been launched to the market and is an important step towards 24/7 water security. Presents a new challenge for the handling of data that come from critical on-line water quality parameters. Requires re-thinking of response to alarms because it is no longer too late to avert disaster. Therefore, the first response is no longer confirmation sampling Instead, the reponse is isolation of contamination by closing valves, disinfection by starting a UV device, etc..