Where Does the Excrement from Mobile Toilets Go?
The destinations of excrement from mobile toilets mainly include natural treatment, septic tank treatment, regular pumping and centralized treatment, as well as various pathways after treatment by different technical types.
In terms of natural treatment, some environmentally friendly mobile public toilets are equipped with fecal tanks. The waste in these tanks is decomposed by bacteria or undergoes biological sedimentation by parasitic earthworms, which break down organic matter and achieve natural purification.
Septic tank treatment utilizes sedimentation and anaerobic fermentation techniques to remove suspended solids and colloidal floating matter from sewage. The purified water can be recycled and reused or discharged into the environment, while the treated feces are used as fertilizer in seepage pits. However, this method has certain drawbacks, such as being prone to causing groundwater pollution.
Regular pumping and centralized treatment are relatively common methods. Mobile toilets usually have sewage tanks at the bottom to collect feces and sewage. When the number of users reaches a certain level or the sewage tank is close to its capacity limit, professional cleaning personnel will regularly pump it to prevent overflow. The pumped feces and sewage are transported to specialized fecal treatment centers for harmless treatment, which may include biological degradation, chemical treatment, or physical treatment methods. Eventually, they are transformed into substances harmless to the environment and can be further converted into organic fertilizers or used for other resource recycling purposes.
Mobile toilets with different technical types also have different treatment methods. For water-flush and waterless-flush pumping types, water-flush types discharge feces into the bottom sewage tank through water tank flushing, while waterless-flush types directly receive excreta in the sewage tank, both requiring regular pumping. Recirculating water-flush types adopt biofilm technology, treating fecal sewage through aerobic and anaerobic processes and adding microbial strains to accelerate decomposition. The treated water is recycled for toilet flushing. Dry-packing types use biodegradable plastic bags to receive excreta, automatically replacing new bags after each use and transporting them to treatment plants in a centralized manner. Foam-sealing types generate foam through foaming liquid to cover the toilet bowl, blocking odors and lubricating for flushing, with extremely low water consumption. The urine is treated into reclaimed water for reuse. Microbial degradation types separate solids and liquids. The solid feces are mixed with wood chips and strains for fermentation, decomposing into carbon dioxide and water (degradation rate ≥ 99%). The urine is treated into reclaimed water through aeration and evaporation, with no pollution emissions throughout the process and organic fertilizer can be produced. Vacuum adsorption types (vehicle-mounted mobile toilets) use vacuum pumps to suck excreta into the fecal collection tank, suitable for vehicle-mounted or mobile scenarios, saving water and facilitating transportation and treatment. Resource-based zero-discharge technologies, such as converting fecal water into organic fertilizer and water vapor through closed-loop fermentation, achieve zero emissions and are suitable for rural areas or regions without pipe networks.
