Recent years, global “water crisis” i.e. freshwater shortage and water pollution has seriously hindered the development of economy and human society, and subsequently aroused the environmental and public health concerns. This work attempts to address these issues by the development of two types of field-based sensing techniques, including on-line monitoring of wastewater quality and in-situ real-time sensing of free ammonia. On the one hand, in order to alleviate the global freshwater shortage, the purified recycled water (PRW), a product regenerated from recycled water, has been considered as an effective alternative water source. In this PRW production process, wastewater is considered as the source water, the effective and reliable wastewater source management tool is therefore required to mitigate potential health risks and safeguard PRW operation. For this purpose, a wastewater quality monitoring system (WQMS) is developed. It employs a wall-jet flow cell embedded with three pairs of specially configured temperature, conductivity and turbidity sensors and a U-shaped flow cell with a pair of incorporated pH sensors.