1 Subjects: “...treatment...”

2 Subjects: “...water and wastewater treatment...”

3 Subjects: “...wastewater treatment...”

4 Subjects: “...heat supply system...”

5 Subjects: “...anaerobic treatment...”

6 Subjects: “...heat production...”

7 Subjects: “...wastewater treatment...”

8 Subjects: “...wastewater treatment...”

9 “..., wastewater treatment digester gas), geothermal, biomass, low-impact hydroelectricity, and emerging...”