Water/Wastewater 25
Figure 1: The relationship between final effluent Turbidity and TSS+BOD - WWTP with standard Percolating Filters
every second. The outstation calculates 15 minute averages (or in the case of temperature takes a 15 min spot reading) and relays the data by a phone line to a central processing unit known as SCOPE. The SCOPE data is available to the Regional Control Centre and local PCs.
Turbidity Probe Mounting
The System serves as a single source of process data with automatically generated performance indicators that allow exception notification and strategic analysis.
An important functionality of the System is Exception Reporting. This function compares the recently archived value with a limit value and generates an Exception Report if the value is out of range. The Exception Report, as an email, is sent to selected recipients.
An Operational Database has been designed to hold asset dimensions and other site details (current operational units and trigger (limit) values) which are used in the calculations.
Reporting of Data Turbidity Probe In Situ
because we have established the skills, tools and spares to ensure that every installation is conducted quickly and efficiently and the quality of the HACH LANGE instruments ensures reliability and accuracy.”
One of the advantages of the SC controllers is the ability to add additional instruments and Clive Murren says: “The facility to add the Nitratax nitrate probe saves time and money when using this platform, because it utilises the same spade design as the turbidity sensor and several of the latest installations have also incorporated the nitrate probe.”
Processing of Data The WWTP telemetry outstation scans all connected monitors
A relationship has been established between the sum of the spot sample TSS + BOD and archived turbidity (see Figure 1).
The turbidity relationship is used to determine a turbidity level equivalent to the sum of the permitted BOD + TSS. This turbidity ‘permit’ equivalent is used by Southern Water in three ways:
1. 80% of the ‘permitted’ turbidity is used in the outstation to generate an alarm in SCOPE if the 15 minute mean turbidity exceeds the ‘permitted’ turbidity for more than a chosen time span. This may be instantaneous or up to 2 hours depending on the environmental significance of the discharge. A high priority alarm is then issued to the site/standby Operator who will visit the site and take appropriate action.
2. The Process Management System generates an Exception Report by email to selected recipients if the daily average turbidity held in the derived values archive exceeds 80% of the ‘permitted’ turbidity.
3. Each Exception Report generated is investigated by the Process Scientist and an ‘Exception Reason’ is chosen from an agreed list of 43 operational and environmental causes of high turbidity - ranging from storm conditions and mechanical failure to equipment malfunction and vandalism. These reasons are then summarised and used for Business Intelligence purposes. In this way Southern Water is monitoring performance of all WWTPs against a continuously monitored parameter in addition to the compliance statistics generated by spot sampling.
Benefits of on-line monitoring
The installation of on-line monitors has encouraged a proactive response to system deterioration, which has resulted in a significant reduction in staff time associated with operational management of the wastewater assets. Non-routine site visits by Operational Staff have been reduced, and Wastewater Support Staff can target their site visits to WWTPs with poor performance as identified by on-line monitors.
The plant performance data has been improved with the use of 35,040 readings at fifteen minute intervals per monitor per year. The consequences have been protection of compliance and the identification of optimisation opportunities.
Routine final effluent sampling has been substantially reduced, resulting in considerable savings in sampling and analytical costs.
Real-time access to turbidity data also helps troubleshooting. For example, high turbidity values can indicate filter rotation problems, hydraulic/organic overload, final tank scraper failure, secondary treatment bypass or tertiary treatment failure.
In addition to the benefits from early warnings of poor quality effluent and the ability to show deteriorating trends, compliance levels have been maintained at around 98% since installation of the monitors began.
Your Key Weapon Against Leaks How can “permanent leak monitoring and
detection technology that leaves no wishes unfulfilled” be put into few words? The answer is Sebalog N3 Network from SebaKMT (Germany).
Once installed, the smart correlating noise logger network saves you a lot of trouble: no more time-consuming patrols, no expensive data transmission, and no unpleasant surprises from critical network sections. With up to 50 correlating noise loggers, several wireless amplifiers, and a GSM transmitter
unit, Sebalog N3 offers you a daily fingerprint of the entire supply network: it permanently monitors your network condition, immediately identifies existing leaks, and locates new ones the moment they appear.
For More Info, email:
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www.envirotech-online.com IET Annual Buyers’ Guide 2013
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