Sustainable retrofitting of Soviet-era heritage bathhouses: greywater reuse and geothermal heat recovery at the Arasan Complex

This paper proposes an engineering framework for sustainable retrofitting of Soviet-era heritage bathhouses through integrated greywater reuse and geothermal heat recovery systems. The study addresses the combined objectives of minimizing environmental impact and preserving the architectural integrity of water-intensive heritage facilities. Using the Arasan Bath Complex in Almaty, Kazakhstan, as a case study, I developed a modular treatment system incorporating ultrafiltration, activated carbon, and ozone disinfection for shower and pool wastewater reuse. A hybrid heating concept integrating geothermal heat pumps with greywater heat exchangers was designed and evaluated. Simulation results indicate a potential 30% reduction in freshwater consumption (30,000 m3 annually) and 29% thermal energy offset. Economic analysis shows a payback period of 5 years for water reuse and under 8 years for geothermal systems. The modular architecture complies with heritage conservation principles while delivering notable improvements in resource efficiency.