Closing the loop: Wastewater treatment becomes more sustainable and nearly carbon neutral
Wastewater treatment plants are one of the most expensive industries in terms of energy requirements – large energy amounts are spent on treating wastewater for reuse or disposal into the environment. According to the International Energy Agency, global electricity consumption for wastewater collection and treatment will require over 60 % more electricity in 2040 than in 2014, as the amount of wastewater in need of treatment increases.
Waste in, resources out
Viewing wastewater treatment plants not merely as waste disposal but rather as resource recovery facilities is important. This means that they have the potential to produce clean water, recover nutrients and safe materials, and reduce reliance on fossil fuels through energy-efficient processes and renewable energy production. Pan-European wastewater treatment innovators came together through the EU-funded SMART-Plant project to explore how technologies that recover valuable materials from wastewater to produce marketable products can be retrofitted into existing sewage treatment plants. What’s more, the project developed new systems for monitoring the energy use and carbon footprint of wastewater treatment.
Smart material recovery technologies
“SMART-Plant developed innovative eco-friendly solutions that provide evidence of how utilities can convert their wastewater treatment sites to become resource recovery facilities, reduce their energy and carbon footprint and digitalise their operations,” notes project coordinator Francesco Fatone. The project demonstrated different technologies (SMARTechs) in seven pilot plants. In the Netherlands, project partners developed a process to separate the cellulose from the incoming sewage water and turn it into clean cellulose fibres. In Israel, partners demonstrated a patented anaerobic biofilter that transforms wastewater into renewable energy (biogas). Spanish partners demonstrated a process called SCEPPHAR to treat wastewater while simultaneously recovering products (up to 50 % of phosphorus and sludge enriched with PHAs, the most promising biopolymers as substitutes for oil-based plastics). The UK pilot demonstrated an ion exchange process to recover ammonia and phosphorus from secondary wastewater, for possible reuse in chemical and fertiliser industries. In Italy, the sidestream SCENA and SCEPPHAR treat sludge liquor, highly loaded with nitrogen and phosphorus nutrients, to remove up to 85 % of nitrogen, recover phosphorus as struvite and produce a sludge enriched with PHA, while decreasing the energy costs up to 20 %. In Greece, thermal hydrolysis coupled with SCENA is developed to treat sludge reject water with high ammonia content. The resources extracted by the SMARTechs (cellulose, nutrients and PHAs) are then formed into products by two ‘Downstream SMARTechs’. The first technology uses cellulosic and PHA materials to make biocomposite plastic that can be used in the construction industry or for consumer goods. The second one consists of dynamic composting to produce commercial fertiliser or biofuel out of cellulosic and phosphorous-rich sludge.
Clearing the hurdles to circular wastewater treatment
The water industry plays an important role in the emerging circular economy that helps keep resources in use for as long as possible. “SMART-Plant believes that water utilities can become the engines of the circular economy if operators replace hesitance and scepticism with an overall positive attitude towards eco-innovative solutions for resource recovery,” explains Fatone. To achieve this, project partners engaged local water utility staff in the large-scale pilot installations, providing training sessions and manuals. “This helped operators perceive how resource recovery systems can gradually change the wastewater management paradigm without disrupting existing assets and workload,” notes Fatone. SMART-Plant’s wide range of technologies reveals that wastewater should not be treated as waste, but rather as a resource.
Keywords
SMART-Plant, wastewater treatment, resource recovery, PHA, cellulose, circular economy, nitrogen, biogas, phosphorous
