Indicators for Sustainability Assessment in the Procurement of Civil. . .
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WWTP 1, the maximum workplace concentration and the applicable occupational
exposure limits of hydrogen sulphide concentration have been exceeded. To stay
within the threshold value, the sand trap should be covered, and the exhaust air
sucked off. For the treatment of the exhaust air, there are three different variants:
co-treatment in the aeration, fume scrubber and UV treatment.
The second example is the renewal of the digester chambers for the WWTP 2.
The WWTP is operated with a mechanical and biological stage. The sludge from
the wastewater treatment are fed to sludge digestion. The variants for this case
example were the renovation of the existing septic tanks, an addition of mixed
sludge dewatering and the construction of the septic tanks.
The third example is the treatment of process water in WWTP 3. During
the dewatering of the sludge, the process water with high ammonium content is
produced. This process water is returned to the main sewage stream. Due to lower
effluent criteria of ammonium in the WWTP the process water must be treated
separately. Consequently, three variants were assessed: Stripping and acid wash,
activated sludge process or deammonification in a sequencing batch reactor.
The fourth example is taken from the sewer system rehabilitation. The so-called
Cured-in-place pipe (CIPP) is one of several trenchless rehabilitation methods
where a resin-saturated felt tube is inserted into a damaged pipe. The liner is inserted
using water or air pressure and dries in place. In this case study a product with
different properties was examined.
3 Results
3.1 Variant Analysis
With the value benefit analysis all case studies could be evaluated. The specific value
for each indicator was determined by the direct ranking method, which allowed a
flexible assessment process. Due to the high number of indicators a consideration
of the three sustainability dimensions simplifies the results. The dimension view
shows the high and low rated dimensions of the variants as it can be seen in Fig. 2
for the case example exhaust air treatment in the WWTP1. A high rating indicates
a positive assessment. In this case example each variant has a high value in one
dimension. Variant 3 has the highest total value but is just in one dimension the
highest rated variant. Variant 2 has the highest rating in the ecological dimension. In
the economic and social dimension, the value is the lowest. Variant 1 is like variant
2, in the social dimension the value is high but the other two dimensions are lower
than the other variants.
In Fig. 3 the DS for the same case example can be seen. The created graphic
shows the three sustainability dimensions. The colours mark the different variants
and therefore the “good” and “bad” aspects of each variant are easy to distinguish.
The same case example shows slightly different results as in the value benefit
111
WWTP 1, the maximum workplace concentration and the applicable occupational
exposure limits of hydrogen sulphide concentration have been exceeded. To stay
within the threshold value, the sand trap should be covered, and the exhaust air
sucked off. For the treatment of the exhaust air, there are three different variants:
co-treatment in the aeration, fume scrubber and UV treatment.
The second example is the renewal of the digester chambers for the WWTP 2.
The WWTP is operated with a mechanical and biological stage. The sludge from
the wastewater treatment are fed to sludge digestion. The variants for this case
example were the renovation of the existing septic tanks, an addition of mixed
sludge dewatering and the construction of the septic tanks.
The third example is the treatment of process water in WWTP 3. During
the dewatering of the sludge, the process water with high ammonium content is
produced. This process water is returned to the main sewage stream. Due to lower
effluent criteria of ammonium in the WWTP the process water must be treated
separately. Consequently, three variants were assessed: Stripping and acid wash,
activated sludge process or deammonification in a sequencing batch reactor.
The fourth example is taken from the sewer system rehabilitation. The so-called
Cured-in-place pipe (CIPP) is one of several trenchless rehabilitation methods
where a resin-saturated felt tube is inserted into a damaged pipe. The liner is inserted
using water or air pressure and dries in place. In this case study a product with
different properties was examined.
3 Results
3.1 Variant Analysis
With the value benefit analysis all case studies could be evaluated. The specific value
for each indicator was determined by the direct ranking method, which allowed a
flexible assessment process. Due to the high number of indicators a consideration
of the three sustainability dimensions simplifies the results. The dimension view
shows the high and low rated dimensions of the variants as it can be seen in Fig. 2
for the case example exhaust air treatment in the WWTP1. A high rating indicates
a positive assessment. In this case example each variant has a high value in one
dimension. Variant 3 has the highest total value but is just in one dimension the
highest rated variant. Variant 2 has the highest rating in the ecological dimension. In
the economic and social dimension, the value is the lowest. Variant 1 is like variant
2, in the social dimension the value is high but the other two dimensions are lower
than the other variants.
In Fig. 3 the DS for the same case example can be seen. The created graphic
shows the three sustainability dimensions. The colours mark the different variants
and therefore the “good” and “bad” aspects of each variant are easy to distinguish.
The same case example shows slightly different results as in the value benefit