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Strathkelvin Instruments/ASP-TOX – Activated Sludge Plant Toxicity Detector

ASP-TOX – Activated Sludge Plant Toxicity Detector

The ASP-Tox system is designed for the online measurement of the Toxicity of an influent to the Wastewater Treatment Plant. Total toxicity and Nitrifying Only Versions are available. The systems are fully compatible with PLC, SCADA and DCS systems and have local alarm trending and individual test data retrieval capability as standard. Remote access, alarm and I/O capability are also provided as optional extras

The ECO-Tox system measures the toxicity of the effluent from a treatment process or a direct discharge to receiving waters. We use cultured Daphnia to measure Eco Toxicity

Self-Cleaning and Self-Calibrating

Testing Principle

The ASP-Tox measures toxicity based on the Respiration Rate/Oxygen Uptake Rate (OUR) of the Activated Sludge Bacteria under synthetic feed conditions when the influent is initially not present and then when the influent is added to the test. The instrument is either located in the Anoxic Zone of the Activated Sludge Process (or as early as possible in the Aerobic Zone) or alternatively it can be located near the Influent streams with the Activated Sludge pumped to the test location.   Testing under optimised feed conditions allows determination of SOUR (Specific Oxygen Uptake Rate), which is monitored as an ongoing indicator of Chronic Toxicity.             ++ 44 (0)1698 730400


Activated Sludge Plant – Toxicity Meter

Test Frequency The operator can program how often the Toxicity test is carried out. As standard a test is completed every 20 minutes but this can be reduced to every 7 minutes. Self-Cleaning The sensors are automatically wiped clean as standard every 12 hours, but this can be reduced to every hour in difficult applications. A water wash is available as an optional extra.
Connectivity Fully compatible with

  • Hardwired fully programmable digital I/O (additional O/I available on request
  • Modbus RTU
  • Modbus TCP I/P

Optional Extras (on request)

  • Hardwired fully programmable analogue I/O
  • Profibus
  • Can Open
  • Profinet

Others on request

Self-Calibration. This measurement is based on Dissolved Oxygen Sensors. These are automatically calibrated by the system for both high and low point, in-situ. The standard calibration frequency is every 7 days but this is operator adjustable.

The control respiration rate is calibrated each time the test is completed.

Technical Support. The ASP-Tox is supplied with a router to allow remote access under operator control. By fitting a SIM card we can provide remote technical support with full fault-finding and result interpretation capability. This service is provided free of charge for the first 3 months and on an ongoing basis to customers who take our service contract. (Fair use conditions apply). For a list of authorised local distributors please check our Distributor page on our website. Consumables. The toxicity detection systems consume approximately 15litres of Synthetic Feed every 10 weeks and the ECO-Tox system consumes approximately 2kgs of Daphnia every 10 weeks.
Maintenance and Servicing. The unit performs best with a 6-monthly   service to replace seals, wipers and sensor slide. A manufacturer’s Service Contract, which can extend the warranty to 7 years, and includes all spares and consumables required, is available globally. Spares Recommendation

  1. LDO sensor slide * 1
  2. Stirrer * 1
  3. Wipers * 2
  4. Seals * 2



Other Strathkelvin Offerings

ASP-Con, ASP-SVI, Strathtox, AS Bioscope & Optimisation & Compliance Consultancy

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Strathkelvin Instruments Limited,

Rowantree Avenue,

North Lanarkshire, ML1 5RX,


01698 730400
Fax: 01698 730401
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