EarlyWarning System for Hazardous Substances in Sewage

ReportNo WSAA 50


December 1992




Illegalor toxic discharges to the sewerage system can compromise the safety of sewerworkers, may result in damage to biological treatment processes and canpossibly cause serious environmental pollution. Sewer discharge points aresampled and analysed regularly, but it is unlikely that a harmful discharge, beit accidental or deliberate, will coincide with the time at which these samplesare taken.


In anattempt to provide an improved level of sewer surveillance, Melbourne Waterobtained a research grant from the Urban Water Research Association ofAustralia to assist in funding an investigation into the feasibility ofcontinuously monitoring sewers for hazardous conditions.


Consequently,CSIRO was contracted by Melbourne Water and the Urban Water ResearchAssociation of Australia to develop an automated on-line sewer monitoringsystem. The “Sewer Sentinel” is based on a package of physico-chemical sensors whichare immersed in a fast flowing sidestream of macerated raw sewage. The sensorpackage is controlled and results logged using customised PC-based software.The system is able to detect discharge events, and can be configured to commandan automatic sampler to collect a sample for subsequent examination andlaboratory analysis.


The“Sewer Sentinel” system has been successfully demonstrated in sewers connectedto industrial estates (CSIRO site, Clayton and Levanswell Rd, Moordialloc), ina domestic sewer (Lower Plenty), and at a regional sewage treatment plant(Brushy Creek). Results are most promising, with the system being able tooperate reliably for at least a month with little attention.


Copiesof the Report are available from WSAA, price $A20. Orders may be placed throughthe Bookshop at www.wsaa.asn.au or by email to info@wsaa.asn.au.