Mobile Toilet Urine Evaporation and Recycling

The urine in mobile toilets can achieve water recovery and resource utilization through evaporation and condensation cycles, with some technologies achieving low energy consumption operation.

Principle of Evaporation and Condensation Cycle Technology

The core technology adopted by Beijing's environmentally friendly mobile toilets is the urine evaporation and condensation cycle. The process is as follows:

1. Urine Heating and Evaporation: The water in the urine is converted into steam through a heating device. This process requires precise control of temperature and time to avoid excessive decomposition of organic matter or excessive energy consumption.
2. Steam Condensation and Recovery: The steam is cooled by a condensation device and converted into reusable reclaimed water. This reclaimed water must meet non-potable water standards such as for toilet flushing to ensure hygiene and safety.
3. Energy Consumption Control: The electricity consumption per use does not exceed 0.3 kilowatt-hours. Low energy consumption operation is achieved by optimizing heating efficiency and condensation paths, making it suitable for the energy supply conditions in mobile scenarios.

Separation and Treatment of Liquids and Solids

Some mobile toilets in Beijing further optimize the treatment process:

• Solid-Liquid Separation: Separate urine from flushing water (liquid) and feces and toilet paper (solids) to reduce the subsequent treatment load.
• Liquid Biological Treatment: The separated liquid enters a multi-layer biofilm reactor, where microorganisms metabolize and decompose organic matter (such as urea and ammonia nitrogen). After treatment, the water quality meets reclaimed water standards and can be reused for toilet flushing, forming a closed-loop cycle.

Urine Resource Utilization Technologies in Other Countries

Gotland Island in Sweden adopts the drying-fertilizer production technology:

1. Urine Drying into Blocks: Most of the water in the urine is removed through high-temperature drying to form block-shaped solids.
2. Crushing and Pressing: The blocks are hammered into powder and then pressed into fertilizer pellets for use in agriculture or gardening. It should be noted: This technology does not involve evaporation cycles but focuses on the solid-state resource utilization of urine, which is different from the reclaimed water recovery goal in Beijing.

Technology Comparison and Applicability

• Evaporation and Condensation Cycle: Suitable for water-scarce areas, reducing toilet flushing water consumption through reclaimed water reuse, but requiring solutions for heating energy consumption and equipment maintenance issues.
• Biological Treatment + Reclaimed Water Reuse: Relies on microbial activity and requires regular water quality monitoring, suitable for scenarios with high hygiene requirements.
• Drying-Fertilizer Production Technology: Suitable for agricultural areas, converting urine into fertilizer, but requiring additional treatment equipment and transportation costs.

In conclusion, the urine treatment technology for mobile toilets should be selected according to scenario requirements (such as water resources, energy, and hygiene standards). The evaporation and condensation cycle is currently one of the feasible solutions that balance water conservation and low energy consumption.