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Three sustainable tools

Every important decision we make is analyzed with three tools for sustainability assessment. Gryaab is located in the port city of Gothenburg on the Swedish west coast. We own and operate one of the the largest wastewater treatment Plants in Sweden, Rya WWTP. Sustainability is at the core of the work we do,  and it is continuously taken into account on every level. This is achieved through the use of three sustainability assessment tools with varying degrees of complexity. While the tools’ different levels of complexity mean that the time consumption and barrier of entry varies between the tools, they have been designed to share the same basic structure, grading scale and overarching criteria. Thus, the results produced should point in the same direction, despite varying degree of complexity. All three tools are Excel-based, and the overarching idea for all three is to compare options based on the three dimensions of sustainability: ecological, social and economic sustainability.

The basic tool for minor changes

The basic tool is applied when implementing minor changes at the plant, such as when a pump is replaced, or a new pH sensor is installed. Rough estimations of how the proposed change affects the three dimensions of sustainability are carried out by the operator proposing the change. The results are then presented to the responsible manager and a decision is made, regarding whether the suggested change is implemented or not.

 

 

 

The intermediate tool used for most of our projects

The intermediate level tool is sufficient for most projects. When using this tool, a group with broad expertise is assembled to grade different options with regard to a number of different criteria. The current criteria list includes 18 different criteria, spanning subjects such as climate impact, cost and safety. The intermediate level tool has been employed in various projects, such as when replacing the compressors that supply air to Gryaabs activated sludge step.

 

The third tool for major decisions with presumably large sustainability impact

The last tool is reserved for major decisions which will impact sustainability over several decades, where advanced calculations are needed in order to accurately quantify sustainability criteria and make informed decisions. This tool is a full-fledged multicriteria tool, and the main difference to the intermediate level tool is that the multicriteria tool has a step for weighting the criteria against each other. This weighting procedure is carried out by the executive management.

The weighting procedure

Weighting of the criteria reflects the opinions of the decision-makers. To support this process we use calculated ratios between annual and the other quantifiable criteria, such as SEK/kg CO2-eqvivalent for the criterium climate impact.

Reserved for larger projects

Due to the time and effort required, this tool is reserved for larger projects. So far it has been used in two projects; to compare different technologies for removal of micropollutants, as well as to compare process options for the planned expansion of the WWTP. The analysis indicated that addition of pulverized activated carbon was inferior to ozonation and granulated activated carbon filters, as a method for removing pharmaceuticals from the wastewater.