Aldi Stores Limited needed a sustainable and cost-effective way to manage wastewater from their newly built 600,000 sq ft distribution centre. The system was designed to manage the wastewater from the construction site, and then manage the full flow and load of the centre when fully operational.

In the end, it needed to treat wastewater for the equivalent of 250 people, with flows up to 50 cubic meters per day and loads of 15 kg/day of biochemical oxygen demand (BOD), 2 kg/day of ammonium (NH4-N), and 1.5 kg/day of total suspended solids (TSS). The discharge would flow through swales into a surface water pond and needed to meet strict environmental permit limits set by the Environment Agency: 20 mg/l BOD, 30 mg/l TSS, and 20 mg/l NH4.

The solution included a packaged wastewater treatment plant and a tertiary horizontal subsurface flow (HSSF) reed bed system. The treated water flows by gravity from the plant into a chamber, distributing it into two reed beds. The water is first screened to remove as many contaminants as possible before biological treatment. The reed beds are planted with Phragmites australis, also known as common reed.

Despite challenging ground conditions during construction, the system was completed in time to handle wastewater from the construction site. By the time the distribution centre was built, the reed beds were fully mature and ready to manage the increased wastewater flow from the fully functioning facility.

The HSSF reed bed system provided Aldi with an efficient, eco-friendly, and cost-effective solution for wastewater treatment. This system not only meets Aldi's wastewater needs but also supports its commitment to sustainability, as outlined in its Global Sustainability Strategy report.