Large wastewater projects often become difficult not because of the UV equipment itself, but because of everything around it: hydraulic calculations, limited installation space, construction schedules and the need to fit the system into infrastructure that has already been designed.
This project involved a contractor working on stormwater and domestic wastewater facilities.
The required total design flow was up to 600 L/s, with UV disinfection planned after sand and oil separation stages.
The equipment had to be installed inside underground tanks approximately 3.2 m in diameter and more than 7 m long.
The original design was undersized
The first version of the project specified two UV units rated at 100 L/s for each treatment line.
After checking the actual hydraulic requirements, it became clear that this configuration would not provide enough capacity.
The UV section therefore had to be redesigned before installation.
This was especially important because the tanks and connecting pipework had already imposed strict limits on the dimensions and orientation of the equipment.
Space was another major constraint
The UV units were not going into an open technical room.
They had to fit inside underground reservoirs, so several practical details became critical:
overall dimensions;
orientation of the inlet and outlet connections;
access for installation and maintenance;
cable length between the UV units and control cabinets;
lifting points;
location of auxiliary equipment.
Even a suitable unit can become difficult to install if these details are not considered early enough.
Two UV reactor configurations
Two multi-lamp flow-through UV units were selected for the revised design.
15-lamp configuration
The first type had:
maximum flow capacity: up to 440 m³/h;
15 amalgam UV lamps;
total installed power: 10.5 kW.
17-lamp configuration
The second type had:
maximum flow capacity: up to 550 m³/h;
17 UV lamps;
total installed power: 12.87 kW.
Eight units were supplied for the project in total.
The source project documentation describes the delivery as groups intended for approximately 150 L/s and 100 L/s duty points on each line. Because the original material does not fully explain how those operating points relate to the overall 600 L/s design flow, it is better to treat them as individual design sections rather than simply adding the nominal values together.
Installation-oriented design
For easier integration into the reservoirs, the UV units were manufactured in a U-shaped configuration, with the pipe connections positioned on the same axis.
Additional details were included specifically for the installation:
lifting hooks;
10 m cables;
stainless-steel housings;
outdoor control cabinets.
The reactor bodies were made from AISI 304 stainless steel. The design also allowed for the use of AISI 316 where required by operating conditions.
Control and maintenance equipment
The project included more than the UV reactors themselves.
The complete configuration also contained:
IP55 outdoor control cabinets;
flushing units;
operating-hour counters;
provision for optional flow sensors;
provision for optional UV intensity sensors.
These components are important in large wastewater installations because the UV system has to remain accessible for inspection and maintenance even when the reactor is installed below ground.
Staged delivery
The customer requested phased shipment so that equipment delivery could follow the construction schedule.
The units were therefore dispatched in several stages rather than as one complete shipment.
This reduced the need to store large equipment on site and allowed installation work to continue as the civil works progressed.
The project also included:
dimensional drawings;
wiring diagrams;
equipment passports;
coordination during unloading.
Project timing
The equipment was produced and delivered within 45 days, earlier than the originally expected completion period.
At the time described in the project materials, part of the equipment had already been installed inside the tanks and was ready for commissioning.
What this project shows
Large UV wastewater systems are rarely a simple equipment-selection exercise.
The final configuration depends on several things at once:
real hydraulic flow;
available installation space;
connection geometry;
maintenance access;
cable routing;
control cabinet location;
construction sequence.
One of the most important lessons from this project is that the hydraulic design should be checked before equipment manufacture begins.
If the design flow is underestimated, correcting the mistake later can affect not only the UV units but also tanks, pipework, power requirements and the entire installation schedule.
For underground wastewater facilities, mechanical integration can be just as important as UV performance itself.
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