Microprocessor control… for a stream engine

Municipal scale UV disinfection systems are expected to operate automatically with little operator intervention. Control software is used to adjust the UV System output depending on flowrate and water quality inputs to maintain the required UV Dose. The control system will flag system operating faults and automatically switch between reactors to minimise the loss of disinfection, in fault conditions.

The Control software enables immediate changes in system operation. Yet traditional mercury lamp UV (Hg UV) systems cannot react at the same pace causing a significant lag in performance which needs to be managed to avoid under-dosing.

For Hg UV reactors, adjustments in UV Dose to accommodate instantaneous flow or UVT changes can be measured in minutes as the rate of change is limited to protect the vulnerable mercury lamps and ballasts.

A loss of one Hg lamp will prompt a reactor shutdown and it will take several minutes for a standby reactor to come up to full disinfection. Meanwhile flow will be either stopped or passed untreated through the system.

But imagine a UV System which can adjust the UV Dose instantly.

Imagine a UV System with no downtime while switching between Reactors.

Imagine a UV System which monitors every single light source and provides instant diagnostics of operating conditions.  

Welcome to the world of UVC-LED.

Disinfection at the speed of (UV LED) light

UVC-LEDs are a solid-state light source which can switch from OFF to full output in only 100 milliseconds and each LED can be switched ON and OFF continuously with no impact on LED life.

For a water treatment application this means that disinfection is available immediately when needed and while the system is operating the UV output is adjusted continuously to meet the required UV Dose, meaning that over-dosing, and wasted power consumption is avoided.

How does it work?

The fundamental operation of a UV LED system is no different to their Hg UV cousins - they shine UV light into the water to inactivate harmful pathogens such as cryptosporidium. UV LED uses the same inputs of Flowrate and Water Quality (UV Transmissivity), and the UV output of the reactor is measured in the same way using inbuilt Intensity Sensors.

The major difference between UV LED and Hg UV system control is that the UV LED system does everything a lot faster.

To accommodate the slow rate of change of lamp output a Hg UV system will aim to deliver a dose well above a specified minimum - with every mJ/cm² above the minimum translating to wasted power consumption.

By contrast a UV LED system can operate at the required dose point and still deliver a greater degree of process safety with the ability to make adjustments faster than the affected flow can reach the reactor.

Hg UV systems measure the UV Intensity at one point along a lamps surface or in many cases at only 1 or 2 points in a whole reactor. Yet solarisation and variations in lamp output can compromise disinfection performance even if the UV Dose suggests everything is ‘healthy’.

A UV LED system can cross references the measured UV Intensity with the output from every single LED providing monitoring of performance throughout the whole reactor.

UV LED technology has the capability to monitor the condition of all critical components so potential issues can be flagged and addressed before they compromise performance.

The Typhon UV LED system has other control features built int the system design particularly suiting 24/7, high flowrate applications including:

In-built redundancy

The Typhon UV LED system can accommodate up to 1% of non-operational LEDs in a reactor and still operate within validation which dramatically reduces the need for operator intervention.

Overdrive

The Typhon system can overdrive the LEDs to maintain the required UV Dose even if the flow and UVT deviate from the design worst case parameters. Delivering an extra level of process safety.

The emergence of UV LED technology challenges specifiers and operators to look beyond the traditional methods of comparing two competing, but fundamentally the same, Hg UV systems to embrace the Operational advantages and Whole Life Cost savings of UV LED.