The electricity consumption and water consumption per tonne of wastewater treated by low-temperature evaporation equipment fundamentally depend on the treatment capacity, equipment type (heat pump/MVR), wastewater characteristics, and heat source configuration. Below are the core ranges and influencing factors for each type, with data benchmarked against industry standard operating conditions (40–60°C, absolute pressure 0.08–0.095 MPa).

I. Electricity Consumption per Tonne of Water Treated (Comparison of Mainstream Heat Pump and MVR Types)

Electricity consumption decreases with increasing treatment capacity. Heat pump types are predominantly fully electrically driven, while MVR types achieve significant energy savings through vapour recompression. Specific ranges are as follows:

Small-scale equipment (≤5 tonnes/day, e.g., laboratories/small workshops):

Heat pump concentration type: 150–180 kWh/tonne water; crystallisation type approx. 180 kWh/tonne water. Smaller units feature reduced heat exchange area and lower heat pump waste heat recovery efficiency, resulting in higher power consumption at the upper end of the range.

Medium-scale equipment (5–10 tonnes/day, e.g., electroplating/electronics industries):

Heat pump concentration type: 120–150 kWh/tonne water; crystallisation type: approx. 150 kWh/tonne water. Economies of scale become apparent, with more stable closed-loop temperature and vacuum control leading to reduced energy consumption.

Large-scale equipment (>10 tonnes/day, e.g., chemical/photovoltaic parks):

Heat pump concentration type: 90–120 kWh/tonne water; MVR low-temperature type: merely 20–45 kWh/tonne water. MVR achieves thermal efficiency exceeding 90% through secondary steam compression cycle heating, resulting in significantly lower electricity consumption than heat pump types.

Special condition adjustments:

High-salinity/high COD wastewater (e.g., cutting fluids, emulsions): electricity consumption increases by 10–20%.

Thermally sensitive wastewater (35–40°C): electricity consumption rises slightly by 5–10% due to lower temperatures.

II. Water consumption per tonne of treated water (including cooling water and reclaimed water metrics)

Cooling water:

Heat pump type: No additional cooling water consumption; condensation heat is recycled via the heat pump, resulting in near-zero water consumption. Some open-loop models require minimal cooling water replenishment (≤0.05 tonnes/tonne of treated water) for vacuum pump sealing.

MVR type: Approximately 0.1–0.3 tonnes/tonne of treated water is replenished for compressor cooling, depending on compressor power and ambient temperature.

Reclaimed Water and Concentrate:

Water recovery rate: 90%–95%, yielding approximately 0.9–0.95 tonnes of reusable condensate per tonne of wastewater treated. Concentrate accounts for 5%–10% of output. Reclaimed water quality achieves COD ≤ 300 mg/L and conductivity ≤ 100 μS/cm.

Make-up water requirement: System leakage/blowdown results in a make-up rate ≤2%, meaning ≤0.02 tonnes of fresh water per tonne of treated water.

III. Key Influencing Factors and Energy-Saving Considerations

Equipment type: MVR models exhibit significantly lower power consumption than pure heat pump types; prioritise MVR for large-scale projects. Heat pump models offer greater cost-effectiveness for smaller installations.

Processing capacity: Unit energy consumption decreases with increasing scale. Select equipment based on actual water volume to avoid over-sizing.

Wastewater Characteristics:

Pre-treatment reducing suspended solids (SS) and hardness minimises scaling and heat transfer efficiency degradation, potentially lowering electricity consumption by 5%–15%.

Operational Control:

PLC triple closed-loop control of temperature, vacuum level, and liquid level, combined with heat pump waste heat recovery, can maintain electricity consumption at the lower end of the range