Carbon footprint
One of INCOPA’s roles is to quantify the environmental impact of coagulants. It is well known that municipal wastewater treatment plants consume energy in their processes, but also has a potential to produce energy in the form of biogas. There are a number of “standard” process solutions when treating wastewater depending on wastewater quality, treatment requirements, available space and perception on what is a good solution or not.
A study on Life Cycle Analysis of different Wastewater Treatment Plant Processes (published in December 2020 by the Swedish Environmental Research Institute (IVL) and co-funded by INCOPA) compares the environmental impact of treating wastewater to two different levels of effluent quality (total phosphorus concentration, 1 mg P/L and 0.3 mg P/L) in three different process configurations (Pre-precipitation, Simultaneous precipitation and Biological Phosphorous Removal). The incoming water quality were the same in all scenarios. Automatic process control in the models was used to achieve similar treatment results for the different processes. The main conclusion of the study is that pre-precipitation with coagulants has the lowest carbon footprint, while Biological phosphorus removal has the highest. The more stringent phosphorus removal limits the higher carbon footprint with still lowest values for pre-precipitation and highest for Biological phosphorus removal.
In 2014, INCOPA completed a Life Cycle Assessment (LCA) of coagulant production. The scope of the LCA study starts from the production of raw materials used to create coagulants and runs to the point they leave the factory gate. This is known as a cradle-to-gate LCA study.
Conducted by the Karlsruhe Institute of Technology (KIT) on behalf of INCOPA, the LCA study found that the cradle-to-gate emissions of all coagulants studied averaged 0.106 kg CO2-eq/mole Fe3+ or Al3+. The value is extremely low.
The considerable difference between the minimum and maximum carbon footprint values (range = 0.013 to 0.436 kg CO2-eq/mole Fe3+ or Al3+) is a consequence of the different raw materials which are used to produce each type of coagulant. Some raw materials have relatively high CO2-eq emissions during their production or their transport to the coagulant production site.
As expected, the use of recycled materials or by-products from other production processes decreases the environmental impact of coagulant production. This highlights the effect of transport-related emissions on coagulant production as recycled materials and by-products are often onsite or come from nearby production facilities.