Water Journal : Current November 2017
www.awa.asn.au 68 correlation between allowable H2S in sewer air and acceptable corrosion rates of≤0.5mm per year. This paper describes collaborative research between Sydney Water, City, University of London (CUL) and Edinburgh Napier University on the use of photonic sensors to measure humidity. The photosensitive sensors used in this study were designed and manufactured specifically for this project by CUL and their collaborators, to meet the requirements for high performance photonic sensors with specialised, tailored coatings, designed to operate under both highly biofouling and corrosive conditions in headspace of gravity sewers. The experimental program was carried out in the headspace of a balancing tank that receives the building's wastewater upstream of the on-site wastewater treatment plant at Sydney Water's Parramatta office. The gaseous hydrogen sulphide concentration typically varied during the day between 5 and 130 ppm by volume USE OF NOVEL PHOTONIC SENSORS FOR HUMIDITY MEASUREMENTS IN GRAVITY SEWERS. Innovation in corrosion monitoring in sewers H Bustamante, L S. M. Alwis, K T. V. Grattan, T Sun, L Vorreiter, J Gonzalez Sydney Water's current Sewer Rehabilitation Program costs about $50 million annually. The program relies on chemical addition to minimise hydrogen sulphide (H2S) transfer from the wastewater to the sewer air, as well as the use of ventilation. Humidity plays a key role in microbiologically-induced corrosion of concrete gravity sewers, and minor reductions in humidity are known to reduce corrosion rates. However, no reliable long-lived (>1 week) humidity sensors are available, thus limiting the development of useful models to better manage corrosion; our experience using commercially available electrical sensors has demonstrated that they typically fail after around one week. Accurate and long-term humidity measurements will enable a quantitative executive summary asset management with relative humidity between 97 and 100%. The temperature of the gas phase was around 20-23 degrees during the day and night. The results indicated that the sensors produced strong dynamic responses and accurately recorded the high humidity levels (between 97 and 100% RH). Furthermore, in two cases where the humidity was rapidly lowered by removing them for exposure to the ambient air, the sensors rapidly responded and measured ~100% humidity when replaced in the overhead tank. Thus, the sensors showed their dynamic capability as they could respond to drastic increases and decreases in humidity. The use of photonic sensors in Sydney Water will both improve the monitoring of humidity and help optimise ventilation.
Current August 2017