Estimation of the possible use of wastewater thermal energy
for the auxiliaries of the treatment facilities

Summary

Through the example of the wastewater treatment facilities of Mayachnyi village in the urban district of Kumertau (Republic of Bashkortostan), the possibility of using the thermal energy of effluent to heat incoming wastewater in order to enhance the biological treatment process, as well as for heating buildings, is studied. A heat recovery scheme with the transfer of thermal energy for heating wastewater in a surge tank using a surface heater «jacket» mounted inside the tank of the pipe register or in a heat exchanger «pipe-in-pipe» installed downstream the tank is considered. The required heat output of the heat pump unit has been determined, and the design parameters of various heat exchange units have been calculated. The technical limitations that complicate using a «pipe-in-pipe» heat exchanger and pipe registers have been identified. The possibility of heating incoming wastewater to 18–25 °C has been demonstrated.

Key words

wastewater , ecology , heat pump , power efficiency , resource conservation , secondary thermal energy , recovery

Feasibility study of using thermal power of wastewater
for improving the efficiency of wastewater treatment facilities operation

Summary

A cost effectiveness analysis of using a system for recovering the thermal power of effluent for heating incoming wastewater to enhance the biological treatment process, as well as for heating the premises of wastewater treatment facilities was conducted. With account of the energy cost in the Republic of Bashkortostan, the operating and capital costs of the proposed method for arranging the heating of wastewater treatment facilities with two alternative options: using gaseous fuel (a block-type gas boiler house) and electric heating devices were estimated. The pay-back period was determined using the overhead cost equivalence method for the proposed design options. The energy efficiency was calculated based on the annual fuel and energy consumption expressed in tons of fuel equivalent. It was shown that the wastewater heating system using a heat pump requires the lowest operating costs (RUB 6.9 to heat 1 m³ of wastewater by 10°C, or RUB 1.3 million per year). The system is also the most energy- and cost-effective since it consumes the minimum fuel equivalent and provides for reducing the cost of expensive primary energy resources by 127 tons of fuel equivalent per year.

Key words

sewerage treatment facilities , heat pump , power efficiency , secondary thermal energy , recovery , pay-back period