Tender for turnkey contract regarding design and construction of a new ozone treatment process at Egaa Wastewater Treatment Plant

Description

There has been a significant change in the composition of the wastewater to the Egaa WWTP due to the expansion of Aarhus University Hospital in Skejby. Pharmaceutical residues have been registered that are above the PNEC values in the discharge from the Egaa WWTP following the expansion of the hospital. This has led Aarhus Municipality to conclude that additional treatment for pharmaceutical residues must be carried out at the WWTP. A 4th treatment step therefore has to be established at Egaa WWTP to achieve sufficient removal of pharmaceutical residues in the effluent. A screening of available treatment technologies and theoretical modelling has been carried out based on the 10 focus substances that can be measured in the effluent from Egaa WWTP. From this, it is concluded that implementing an ozone treatment in front of the existing sand filter will be enough to remove the remaining pharmaceutical residues. Lot 1: Aarhus University hospital is located in the catchment area to Egaa WWTP. A study has been conducted mapping the amount of pharmaceuticals in the sewage from the hospital, in the inlet to Egaa WWTP, and in the outlet from Egaa WWTP. Based on the study it was found that 87 % of the pharmaceuticals are coming from household sewage. It was also found that 10 out of 62 pharmaceuticals are above the PNEC value in the outlet from Egaa WWTP. Therefore, it was concluded that the highest environmental value was obtained by centralizing the removal of pharmaceuticals at Egaa WWTP. Based on a literature study and modelling it was concluded that an ozone-based solution is the most suitable technology to remove the 10 pharmaceuticals from Egaa WWTP. Prior to the tender, market dialogue meetings have been held with interested market parties. A summary of the written feedback from the market dialogue are enclosed as annexes to the tender. Aarhus Vands vision is to build an ozone plant for removing pharmaceuticals from the treated wastewater after the clarifiers and before the sand filtration. The ozone plant shall hydraulically be integrated into the operation of the existing treatment plant and must not interfere negatively with the existing treatment of the wastewater, neither must the ozonation increase the energy consumption or the N2O emissions in the existing process steps. The ozonation plant shall be energy-optimized and be able to remove the 4 pharmaceuticals down to the outlet requirements, without exceeding the requirements for bromate. When designing the plant, great focus should be put on working environment, as regards service, maintenance, and safety. The solution must be easy to control automatically based on online sensors, and the equipment must be chosen thus both high and low hydraulic load can be handled in a safe and effective way. To prepare for the future, the solution should be modular, flexible, and easy to extend. Architectural the ozonation facility must be adapted so it matches the existing facility and fulfil the requirements for local planning. Basis of agreement for the new ozone treatment process at Egaa WWTP is as a turnkey contract in accordance with the ‘General conditions for general contracting in construction and civil engineering (ABT 18)’. Agreements about execution of turnkey contracts within construction work for Aarhus Vand can be entered into on the grounds of ABT 18 with Aarhus Vands precisions and deviations.