AUTOMATIC BALLAST WATER TESTING SYSTEM
The BallastWISE test kit is the only completely portable solution based on image analysis, which enables detection of both autotrophic and heterotrophic organisms. The method makes addition of chemicals and other forms for sample preparation unnecessary.
BallastWISE detects and counts living heterotrophic and autotrophic microorganisms within two size-ranges: 10 – 50µm and >50µm, by using high resolution cameras, light-emitting diodes and image analysis algorithms.
After analysis, a one-page document is created automatically, showing the number of organisms detected, making it easy to provide an official report. The report states if the number of organisms is within the limits stated by the IMO ballast water convention and US Coast Guard.
The equipment is contained within a durable, waterproof case, to make for quick transport in the field, on board a vessel, or in the lab.
Heterotrophic organisms get their energy by consuming organic matter, often in the form of other organisms. This group is comprised of a wide range of lifeforms, such as bacteria and zooplankton.
Autotrophic organisms use inorganic sources, such as light, to get energy. In ecological contexts, they are known as producers, making the biomass consumed by heterotrophic organisms. Many algae species are autotrophic.
BallastWISE can analyze a sample of water and find:
- The number of organisms that are swimming
- The number of organisms containing chlorophyll
- The size of each individual organism
Organisms that contain chlorophyll and/or swim are alive with a high degree of certainty.
Optical assembly: BallastWISE uses industrial video cameras for directly viewing individual organisms in their respective size ranges of 10-50µm and >50µm. The magnification is 1x for the smaller fraction and 0.1x for the larger fraction, giving a depth of field of 0.7mm and 20mm, respectively.
Fluorescence: The “standard” method of viewing chlorophyll by stimulation at a wavelength of 420nm and viewing through a high pass filter is used. A special feature of BallastWISE is that it can see chlorophyll within individual organisms, which light up against a uniformly dark background, and it can thereby also measure the size of each one.
Motion detection: Not all microorganisms contain chlorophyll for photosynthesis Some are predators (heterotrophs) most of which swim to encounter their prey. Any swimming organism is evident in the video stream and can be tracked. The software must do this in real time for speed and simplicity, typically at a rate of 15 frames per second. This is computationally demanding and requires efficient algorithms and the use of parallel processing. When illuminated with white light, a background subtraction algorithm is used so that only objects that are moving against the background are analyzed. When illuminated for fluorescence, all objects are analyzed regardless of whether they are moving or not and BallastWISE counts the total number of fluorescing organisms as well as the number of fluorescing organisms that are swimming.
Mechanics and Assembly: BallastWISE analyses both size fractions using two separate cameras. Each camera examines an optical chamber which is filled with a portion of the water sample to be analyzed. Optical chambers are disposable, so new ones can be used prior to any analysis. The larger chamber requires two pumps, one for filling and one for emptying, and both are connected to a nipple at the bottom of the chamber. The smaller chamber is a flow through type and thus needs only one pump. Pumps and lights are controlled via a microprocessor and solid-state relays. The synchronization of the pumping, illumination, and video analysis is all performed by the main application program running on the computer. A framework to hold the pumps, optical chambers, lights, and cameras is built of aluminum and is designed to fit into a case.
Operation: The analysis of a typical sample is performed in the following way:
- Inserting optical chambers into their fixtures and attached tubes through respective pumps, with inflow tubes placed into the water sample to be analyzed.
- Starting the analysis on the application front panel.
- Optionally following the analysis as it progresses. Most aspects of the automatic handling of samples of both size fractions are done in parallel. The operator can view the video streams as they are being processed and follow the tracking of organisms, which are shown as overlays on the live video. To accurately measure organism size and to detect motion, the water in the samples must be still. To achieve this, the sample is pumped into the chamber and the computer waits to allow water movement to stop. Waiting time is longest for the larger chamber. Several chambers need to be analyzed for each size fraction for statistically sound results.
- Examining results which are shown as the estimated number of live organism concentrations within the respective size classes with appropriate warnings if numbers are high. A corresponding one-page report is generated. Track coordinates and organism size data resides in a database.
TRACKS OF Tetraselmis suecica (10µm)
- Weight: 6.4kg
- Dimensions: 38 x 31 x 18 cm (l x h x w)
- Power requirements: 12 – 19V (100 – 250V mains adapter or from external computer battery bank), peak current 2A
- Optical resolution: 2.4µm (10 – 50µm), 22µm (> 50µm)
- Organism sizes: Calculated for each individual as equivalent ellipse minor axis. Minimum detection width = 2x optical resolution.
- Velocity range: 0.024 – 0.6mms-1 (10 – 50µm), 0.22 – 22mms-1 (> 50µm)
- Sampling accuracy 10 – 50µm: 10 ± 50%, 20 ± 30%, 30 ± 20%, calculated per ml at 95% confidence.
- Sampling accuracy > 50µm: 10 ± 30%, 20 ± 25%, 30 ± 20%, calculated per l at 95% confidence.
- Max concentrations: 20,000 per unit volume (ml, l)
- Measurement time: 20-30min
- Sample sizes: 400 mL 10-50µm, 650 mL for >50µm
- Chl a detection: Approx. 5% of a single Tetraselmis suecica (reference organism) cell content (10 – 50µm)
- Output: Video files (optional), tab-separated data files (position and size) for each organism at each point in time
- Reports: Final result counts with risk assessment, size distributions (optional), track plots (optional)
- Minimum computer requirements: 8GB RAM, quad core CPU (PassMark CPU benchmark > 10,000), hard drive write speed > 120MB/s (PassMark Hard Drive benchmark > 7,000)
ANALYSIS OF A NATURAL SEA WATER SAMPLE
This is an example of how BallastWISE works. In the background you see tracks of swimming microorganisms in the greater than 50µm range. In the histogram you see the microorganisms size destribution. Only those that are greater than 50µm are actually counted.