Membrane for ENERGY and WATER RECOVERY

PROJECT DESCRIPTION

BACKGROUND

More than 500 million people in Europe generate around 27 billion m³ of municipal wastewater each year. Municipal wastewater treatment plants (WWTPs) consume large amounts of energy. For example, WWTPs in Germany use around 4400 GWh/year, the equivalent to roughly 1% of the country’s total net electricity consumption per year.

Currently, most WWTPs use aerobic processes which consume a considerable amount of energy. Bioreactor aeration can use as much as 60% of total WWTP energy consumption.

Costs related to such wastewater treatment are expected to rise due to increasing restrictions on the discharge of treated water (EU Water Framework Directive 2000/60/EC) and sludge disposal. Such restrictions represent a significant challenge for treating wastewater. Furthermore, new regulations related to the mitigation of greenhouse gas emissions could penalise both energy consumption and sludge production.

OBJECTIVES

The LIFE MEMORY project aims to demonstrate (at an industrial prototype scale) an anaerobic technology, using the innovative Submerged Anaerobic Membrane Bioreactor (SAnMBR) technology, as an alternative to traditional urban wastewater treatment. The SAnMBR technology combines anaerobic digestion and membrane technology, allowing for the treatment of urban wastewater at ambient temperatures. Anaerobic digestion allows the conversion of the organic matter into a biogas flow (composed mainly by CH4 and CO2) that can be used at the WWTP to generate heat energy and electric power. On the other hand membrane filtration allows the sludge retention time (SRT) to be increased by 100% without increasing the reactor volume – thus in turn permitting anaerobic processes to be used for low-loaded wastewaters. Low growth rate of anaerobic bacteria coupled to longer sludge retention time reduces sludge production, so that there is less residual waste to be disposed of and fewer emissions.

This new approach focuses on a more sustainable concept, where wastewater converts into a source of energy and nutrients, and also a recyclable water resource by membrane disinfection.

The project will demonstrate the economic feasibility of using SAnMBR technology for treating urban wastewater in a pilot plant consisting of an anaerobic reactor with a total volume of 7m3 connected to two membrane tanks, each one with a total volume of 1m3.

Expected results:

Reduction of the energy consumption per m3 of treated water by 70%: the expected results would be a net consumption of only 0.11 kWh/m3 when treating sulphate-rich urban wastewater, and -0.10 kWh/m3 (net energy production) for low sulphate urban wastewater. Compared to typical consumption ratios in WWTPs based on CAS process (0.25-0.6 kWh/m3) and aerobic MBR systems (0.50-2.5 kWh/m3), the proposed technology offers a significant reduction in electricity consumption and the related carbon footprint;

Reduction of CO2 emissions from the oxidation of organic matter by 80%, passing from (in CO2 equivalents) 2.4 kg CO2/kg COD eliminated to 1.4 kg CO2/kg COD eliminated;

Reduction by 50% of sludge production (kg TSS/kg COD removed) compared to aerobic processes;

Reduction by 25% of the space requirement for the treatment facilities compared to the conventional, ‘aerobic’ WWTPs; and

Establishment of a protocol for the design and operation of WWTPs based on this new technology.