The Proteus is a new product providing users with a robust, repeatable, low maintenance sensor platform for measuring coliforms in real-time. The Proteus is underpinned by comprehensive research exploring the use of in-situ fluorescence as a technique for real-time coliform measurement. The Proteus is a multi-parameter instrument that can incorporate a range of optical sensors. The configuration for microbial monitoring includes a tryptophan-like fluorescence (TLF) sensor, turbidity sensor and thermistor which provides users a real time measurement of total coliforms, negating the need for the standard laboratory analysis. Using a robust correction algorithm the tryptophan signal is corrected, in real time, for known interferrants. The result is a repeatable and highly accurate measurement that can provide instantaneous coliform measurements.