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The online and accurate monitoring of drinking water supply networks is critically in demand to rapidly detect the accidental or deliberate contamination of drinking water. At present, miniaturized water quality monitoring sensors developed in the laboratories are usually tested under ambient pressure and steady-state flow conditions; however, in Water Distribution Systems (WDS), both the pressure and the flowrate fluctuate. In this paper, an interface is designed and fabricated using additive manufacturing or 3D printing technology—material extrusion (Trade Name: fused deposition modeling, FDM) and material jetting—to provide a conduit for miniaturized sensors for continuous online water quality monitoring. The interface is designed to meet two main criteria: low pressure at the inlet of the sensors and a low flowrate to minimize the water bled (i.e., leakage), despite varying pressure from WDS. To meet the above criteria, a two-dimensional computational fluid dynamics model was used to optimize the geometry of the channel. The 3D printed interface, with the embedded miniaturized pH and conductivity sensors, was then tested at different temperatures and flowrates. The results show that the response of the pH sensor is independent of the flowrate and temperature. As for the conductivity sensor, the flowrate and temperature affect only the readings at a very low conductivity (4 µS/cm) and high flowrates (30 mL/min), and a very high conductivity (460 µS/cm), respectively.

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The miniaturised online sensors that were developed in the laboratories were for atmospheric pressure and steady state flow, but in the water distribution network neither the pressure nor the flow is steady. Many of the state of the art drinking water quality monitoring sensors can be operated well below the drinking Water Distribution System (WDS) pressure. Moreover, each of the sensors requires different flow rates. This paper discusses simulation and design of an affordable constant flow and constant outlet pressure system and shows an easy way to provide different flow rates for different sensors. The other criterion which should be met is the flow rate of the water bled (leakage) from WDS which must also be low. To meet the above criteria a 2-D model was developed to represent the constant pressure constant flow system for online water quality monitoring (WQM) sensors. Different configuration of the system is considered and the optimum design includes 1.044 m/s flow velocity which is low enough for the flow to be steady.