Hawaii Water Quality Monitoring Protects Local Beaches

Mixing and dilution of effluents discharged into the ocean is an important aspect of the health of ocean users and the ecology of the denizens. In an effort to monitor the path of wastewater making its way into the Pacific water off of Oahu, the EMM2.0 coastal buoy has been selected as a measuring tool for the discharge of pipe effluent (sewage water) 800 ft offshore to ensure that the wastewater discharge was in fact moving away from shore to avoid affecting local beaches.

With the use of temperature nodes within Thermistor strings, water columns were measured to detect the quality of the water along with downward-looking SonTek Acoustic Doppler Profilers (ADP’S) used to check the water’s current profile.

The Oceanit Center in Honolulu was selected to lead this project. According to Technical Director, Dayananda Vithanage, the group will investigate a wastewater outfall extension from 200 ft to 300 ft depth on the south shore of Oahu. The deeper of the two locations is west of the entrance to Pearl Harbor. The maximum currents in the area are expected to be about 2 knots and summer swells can be as high as 3 meters.

Equipment and systems used in this application include:

Buoy Configuration 

• Line of Sight Communications; 900MHz
• Campbell Scientific CR1000 data logger with customer written firmware
• Custom fabricated Stainless Steel frame to hold Acoustic Doppler Profiler in a downward-looking position.
• Closed-cell Ionomer Foam hull, galvanized frame, and aluminum superstructure

Thermistor Strings 

• Thermally sensitive resistor either with Negative Temperature Coefficient of resistance (NTC) or Positive Temperature Coefficient of resistance (PTC)
• Advantages including sensitivity, interchangeability, two-wire connections, ruggedness, hermetic seal, and flexibility
• Capabilities ranging from custom profiles, special testing, Institute of Standards and Technology (NIST) traceability, and Standard Platinum resistance thermometers (SPRT’s)

SonTek Acoustic Doppler Profiler 

• Profiling rangers up to 180m with proven SonTek reliability
• Side-looking configuration used for horizontal profiling
• Bottom Tracking and GPS inputs for moving boat applications and Compass with 2-Axis Tilt sensor
• Temperature sensor and low power consumptions

Additional Blog Posts of Interest:

Monitoring Coral Reefs in the Caribbean: Protecting Our Rainforests of the Ocean 

Water Quality Monitoring Technology Protects One Million People

Water Instrumentation Provides Insight for Ecological Research

Water Quality Monitoring Aids Conservation of Threatened Lake