Table 3
Key Performance Indicators for water management.
| N. | KPI Name | Description | U.M. | Scope-Facilities | Calculation/Evaluation method |
|---|---|---|---|---|---|
| 1 | Total freshwater withdrawal | Water quantity extracted from steelworks sources (e.g. wells or rivers) | m3 | – | Measured |
| 2 | Specific water consumption | Amount of water used when a ton of steel is produced. | m3/tss (m3/tLS) | It assesses water use technology and measure water saving effectiveness | Total water use (m3)/Produced steel (tss or tLS) |
| 3 | Percentage of blowdown water | Ratio between water discharged into the water body and water withdrawal for industrial use | % | It measures the percentage of discharged water with respect to the total water withdrawal | (Discharged Water (m3)/Total water withdrawal (m3))*100 |
| 4 | Specific freshwater consumption | Direct specific use of fresh water for steel production | m3/tss (m3/tLS) | It measures the water efficiency | Total freshwater withdrawal/Produced Steel (tss or tLS) |
| 5 | Specific recycled water | Amount of water recycled per ton steel. | m3/tss (m3/tLS) | It reflects water-recycle technology. | Recycled Water/Produced Steel (tss or tLS) |
| 6 | Specific sewage emission | Amount of sewage emission per ton steel. | m3/tss (m3/tLS) | It assesses water saving effectiveness and the environmental impacts. | Discharged Water (m3)/Produced Steel (tss or tLS) |
| 7 | Specific water losses | Amount of water losses per ton steel | m3/tss (m3/tLS) | It is useful for closing the water balance and in order to evaluate possibilities of losses recovery | (Total freshwater withdrawal – Discharged Water (m3))/Produced Steel (tss or tLS) |
| 8 | Water resource efficiency (γ) | Comparison between fresh water consumption and total water consumption in a specific production process | – | It indirectly assesses the use of industrial fresh water and water use technologies | γ = 1/Fresh water consumption/Total water consumption) |
| 9 | Water circulation rate (μ) | Ratio of recycled water to the total water consumption | % | It assesses water resource use and water use technology | μ = Recycled water consumption/Water consumption x 100% |
| 10 | Water environmental efficiency (η) | Reciprocal of sewage emission per ton steel. | tss/m3 (tLS/m3) | It assesses the environment friendly degree during water consumption. | η = 1/Specific Sewage emission |
| 11 | Change in total suspended solids (TSS) | Difference between TSS (mg/L) in discharged/treated water and TSS (mg/L) in incoming water | mg/L | It assesses treatments efficiency in removal of TSS | TSS in discharged/treated water – TSS in incoming water |
| 12 | Change in chemical oxygen demand (COD) | Difference between COD (mg/L) in discharged/treated water and COD (mg/L) in incoming water | mg/L | It assesses treatments efficiency in removal of COD | COD in discharged/treated water – COD in incoming water |
| 13 | Change in biochemical oxygen demand (BOD) | Difference between BOD (mg/L) in discharged/treated water and BOD (mg/L) in incoming water | mg/L | It assesses treatments efficiency in removal of BOD | BOD in discharged/treated water – BOD in incoming water |
| 14 | Change in bacteria load (BL) | Difference between BL (CFU/mL) in discharged/treated water and BL (CFU/mL) in incoming water | CFU/mL | It assesses treatments efficiency in removal of bacteria | BL in discharged/treated water – BL in incoming water |
| 15 | Change in electrical conductivity (EC) | Difference between EC (μS/cm) in discharged/treated water and EC (μS/cm) in incoming water | μS/cm | It assesses efficiency of treatments/water management in EC control | EC in discharged/treated water – EC in incoming water |
| 16 | Change in Hardness (Ha) | Difference between Ha (°fH) in discharged/treated water and Ha (°fH) in incoming water | °fH | It assesses efficiency of treatments/water management in the Ha control | Ha in discharged/treated water – Ha in incoming water |
| 17 | Specific additives used | Additives with different purposes (biocides, anticorrosive, anti-scaling agents, detergents) that are added into the circuits | g/L (L/m3) | It quantifies the total amount of used additives | Sum of all the exploited additives (g or L)/Total water use (m3) |
| 18 | Energy consumption for water treatment | Amount of energy consumed during the treatment of process water | kJ | – | Sum of the energy consumed during the treatment of process water |
| 19 | Energy consumption for water pumping | Amount of energy consumed by the pumps | kJ | – | Sum of the energy used by the pumps |
| 20 | Other energy consumption related to water management | Amount of energy consumed during management of water that is not included in KPIs 16 and 17 | kJ | – | Sum of the energy in water management (no treatment, no pumps) |
| 21 | Total energy consumption | Total energy consumption for water management | kJ | – | KPI 16 + KPI 17 + KPI 18 |
| 22 | Specific energy consumption | Specific energy consumption | kJ/tss (kJ/tLS) | It measures the specific energy consumption related to water management | KPI 19 (kJ)/Produced Steel (tss or tLS) |
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