WTW OxiTop IS6 and OxiTop IS12 Biochemical Oxygen Demand (BOD) Analyzers

Overview

The WTW OxiTop IS6 and OxiTop IS12 are fully automated, mercury-free biochemical oxygen demand (BOD) analyzers engineered for precision, safety, and operational simplicity in routine water quality laboratories. Based on respirometric pressure measurement, these instruments quantify the dissolved oxygen consumed by aerobic microorganisms during the biodegradation of organic matter in water samples over standardized incubation periods—typically 5 or 7 days (BOD₅, BOD₇). Unlike classical manometric methods relying on toxic mercury columns, the OxiTop system employs a solid-state piezoresistive pressure transducer to detect minute pressure differentials resulting from oxygen depletion within sealed, temperature-stabilized BOD bottles. This eliminates mercury exposure risks while maintaining full alignment with internationally recognized test protocols—including DIN 38409 Part 52 and ISO 5815-1:2019—ensuring regulatory acceptability for environmental monitoring, wastewater treatment compliance, and drinking water safety assessments.

Key Features

• Mercury-free respirometric detection: Utilizes a calibrated piezoresistive pressure sensor to measure O₂ consumption without hazardous materials—fully compliant with RoHS and EU Directive 2011/65/EU.
• Automated 5- or 7-day measurement cycle: Stores one BOD value per day for up to five consecutive days (BOD₁–BOD₅) or supports extended BOD₇ protocols with manual retrieval.
• Integrated AutoTemp™ temperature compensation: Continuously monitors sample temperature; delays measurement initiation until thermal equilibrium is achieved (stabilization window: 0.5–3.5 h), minimizing drift due to thermal transients.
• Constant-speed magnetic stirring: Ensures homogeneous oxygen distribution and consistent microbial activity across all sample volumes, critical for reproducible BOD kinetics.
• Dual-button intuitive interface: “M” button displays real-time pressure-derived BOD value; “S” button recalls stored daily results—no PC or software required for basic operation.
• Robust field-deployable design: Compact, battery-powered (2 × AA, ~12-month life), CE/UL/cUL/TÜV-GS certified—suitable for both fixed-lab and mobile environmental sampling workflows.

Sample Compatibility & Compliance

The OxiTop IS6 and IS12 accommodate standard 250 mL or 500 mL BOD bottles (glass or PET) with integrated sealing caps containing the pressure sensor module. Sample types include raw and treated wastewater, surface water, groundwater, and effluent streams. The system meets the methodological requirements of DIN 38409-52 (German standard for BOD determination), ISO 5815-1:2019 (Water quality — Determination of biochemical oxygen demand after n days — Part 1: Dilution and inoculation method), and supports data traceability aligned with GLP principles. While not inherently 21 CFR Part 11 compliant (as it lacks electronic signature or audit trail functions), its analog-digital hybrid architecture enables seamless integration into validated LIMS environments via optional RS232 output modules (e.g., OxiTop Connect).

Software & Data Management

Standalone operation requires no software—the instrument autonomously records, compensates, and stores daily BOD values internally. For enhanced data handling, the optional OxiTop Connect interface allows direct transfer of time-stamped BOD series (including pressure readings, temperature logs, and stabilization timestamps) to Excel or laboratory information management systems (LIMS). All stored values retain their native resolution (0.1 mg/L below 100 mg/L; 1 mg/L above), and pressure-to-BOD conversion follows the stoichiometric relationship defined in ISO 5815-1 (1 mg O₂/L ≈ 0.355 hPa at 20 °C in 250 mL bottle). Calibration is factory-performed and verified annually per manufacturer recommendations.

Applications

• Regulatory compliance testing for municipal and industrial wastewater discharge permits (e.g., EPA NPDES, EU Urban Wastewater Treatment Directive).
• Performance evaluation of biological treatment units (activated sludge, trickling filters, MBRs).
• Environmental impact assessments (EIA) and baseline water quality surveys in rivers, lakes, and estuaries.
• Research on biodegradability kinetics of emerging contaminants (pharmaceuticals, surfactants, microplastics leachates).
• Quality control in drinking water production facilities assessing post-filtration biostability.
• Educational laboratories requiring safe, repeatable BOD methodology for undergraduate and graduate environmental science curricula.

FAQ

How does the OxiTop eliminate mercury while maintaining accuracy?
The system replaces mercury manometers with a high-stability piezoresistive transducer that measures pressure drop proportional to O₂ consumption. Calibration against certified reference standards ensures traceability to SI units and equivalence with classical methods.
Can I measure BOD₇ or other non-standard incubation periods?
Yes—the device records daily values for five days by default, but users may manually retrieve readings on Day 7. Extended incubation requires operator-initiated readout beyond the auto-store window.
Is temperature correction applied automatically during calculation?
AutoTemp™ continuously monitors sample temperature and applies real-time compensation to pressure readings using the ideal gas law and known solubility coefficients—no manual input required.
What maintenance is required?
Annual sensor verification and cap seal inspection are recommended. No routine recalibration is needed under normal use conditions.
Are the IS6 and IS12 functionally identical?
Both share identical measurement technology and firmware. The IS12 supports dual-bottle simultaneous measurement (two independent sensors), whereas the IS6 operates one bottle per unit—enabling parallel testing or redundancy configurations.