Project Details
| Size | 3,000 m³/day |
| Location | Malta |
| Completed | 2025 |
Project Delivery
| Features | Upgrading an existing wastewater treatment plant |
| Space-saving design | |
| Support in case of excessive inflow | |
| Treatment Modules | ClearFox® FBBR |
| ClearFox® Clarifier |
Project Results
| Before | After | |
| COD | 950 mg/l | <175 mg/l |
| BOD | 420 mg/l | <30 mg/l |
| Ntot | 73 mg/l | <15 mg/l |
| Ptot | 10 mg/l | <2 mg/l |
Discussion
Situation
Malta is a small island in the Mediterranean with a population of around 500,000. The coast that surrounds the country is characterised by clear, clean and revitalised water. To protect and preserve this, the island operates three municipal sewage treatment plants.
One of them was receiving significantly more wastewater than it was able to treat – around 3,000 cubic metres per day. The environmental authority therefore asked for a solution to expand the existing plant. The original plant is a conventional activated sludge plant, which is widely used in municipal wastewater treatment.
There is hardly any industry in the immediate vicinity of the plant. Therefore, the inflow is mainly limited to domestic and agricultural wastewater. The environmental authority therefore stated the COD at around 950 mg/l and the BOD5 at around 420 mg/l. In addition, a TSS value of 570 mg/l, a nitrogen content of 73 mg/l and a phosphorus content of 10 mg/l.
Problem
The operator’s requirement was to reduce the specified pollution parameters by 70 to 90 per cent.
The challenge here was the limited space available for the expansion. The plant itself is located directly by the sea. The surrounding terrain is rocky and slightly hilly. Therefore, the construction of a new aeration tank was not an option.
The plant is also difficult to access. Only narrow, winding roads lead to the plant itself, making heavy equipment or construction work almost impossible. Coordinating and procuring the appropriate plant technology on the island involves additional effort.
Solution
The solution for this project was a modular containerised wastewater treatment plant from PPU Umwelttechnik GmbH. The core components are the ClearFox® fixed-bed process and ClearFox® lamella clarifier, which are installed in a total of 16 containers. A 40ft container receives the wastewater and distributes it evenly to the fixed-bed process. This is installed in a total of twelve 40ft containers. Two 20ft containers and half a 40ft container contain the lamella clarifier. The remaining half contains the control technology.
PPU Umwelttechnik GmbH uses rotationally moulded tanks to contain all the treatment processes. Thanks to the special manufacturing process, they have neither welded seams nor predetermined breaking points. They completely fill a 20ft and a 40ft container so that they make optimum use of the available space.
The first 40ft container contains four tanks that initially collect the wastewater. From this container, a pump system distributes the wastewater evenly to the twelve fixed-bed containers. The ClearFox® fixed-bed process is one of the most robust and reliable biological wastewater treatment systems on the market. The entire containers are filled with net-shaped cubes – the so-called fixed bed material. The microorganisms from the wastewater settle on them and form a biological lawn. With the addition of oxygen, they break down the contaminants in the wastewater. While the front part of each container contains fixed bed material with a smaller growth surface, this increases more and more in the rear part. The system thus cleans the wastewater continuously.
This process produces secondary sludge. This consists mainly of microorganisms that detach themselves from the fixed bed material. This is another positive effect of aeration: it removes used, dead biological lawn from the fixed bed material and thus also prevents the system from clogging.
This sludge first sinks to the bottom of the system. From there, it is pumped, together with the treated wastewater, into the lamella clarifier. This physical sedimentation process separates the sludge from the clear water. While the sludge sinks to the bottom, the clear water collects in the upper part. There it flows out of the plant via an overflow.
The PPU Umwelttechnik GmbH team was responsible for the complete engineering of the plant, based on the conditions on site. The employees at the main production centre in Bayreuth completely dismantled all the containers. This limited the installation time on site to just a few weeks. The plant has been in operation since January 2025 and has been delivering outstanding treatment performance ever since.
