Working Principle of the Fecal Tank in Mobile Toilets
The working principle of the fecal tank in mobile toilets varies based on the design type, mainly falling into three categories: fecal-tank-equipped, septic-tank, and modern fecal-treatment technologies. The core of all these types revolves around the collection, treatment, and transfer of excreta.
Fecal-Tank-Equipped Mobile Toilets
In this type of toilet, the fecal tank is an independent, sealed container. Excreta falls directly into the tank through the toilet bowl. Degrading agents or deodorizers are pre-placed inside the tank to decompose solid waste and neutralize odors through chemical or biological actions, reducing gases produced by decay. Some models are equipped with a simple flushing system that uses a small amount of water or environmentally friendly cleaning solution to flush the toilet bowl and keep its surface clean. When the fecal tank approaches its capacity limit, professionals replace it with a new tank using specialized equipment, and the waste is transported to designated treatment sites for harmless treatment (such as composting, incineration, or landfilling). This design is suitable for temporary events, construction sites, etc., with advantages including simple structure and convenient cleaning and transportation. However, regular maintenance is required to prevent odor leakage.
Septic-Tank Mobile Toilets
The septic-tank type adopts a fecal storage tank structure. After excreta enters the tank through the fecal inlet, solid-liquid separation is achieved through natural sedimentation: solids settle to the bottom to form a sludge layer, while liquids float to the top as a clear liquid layer. Microorganisms (such as anaerobic bacteria) inside the tank decompose organic matter, producing gases like carbon dioxide and methane, which are vented through an exhaust system to prevent pressure buildup. Some designs add biological enzymes or chemical agents (such as oxidants) to accelerate decomposition and shorten the fermentation cycle. During regular cleaning, the bottom sludge needs to be pumped out and the upper liquid treated to prevent solid buildup from clogging the pipes. This design is suitable for long-term use scenarios but requires sufficient space and good ventilation.
Modern Fecal-Treatment Technologies in Mobile Toilets
Modern technologies integrate a "dry-wet separation + biological degradation + vacuum transfer" system:
- Structural Design: The fecal storage tank below the toilet bowl is isolated from the outside, and sewage and solids are quickly separated through pipes to reduce mixed pollution.
- Solid Treatment: Physical dehydration (such as centrifugal force or mechanical squeezing) is used to remove moisture, or microbial inoculants are added to accelerate biological degradation, converting solids into harmless residues.
- Transfer System: When the container is full, excreta is pneumatically transferred to municipal sewers or transfer stations through high-pressure pumps or vacuum sewage trucks, avoiding the long residence time of traditional fermentation and improving cleaning and transportation efficiency. This technology is suitable for high-traffic public places, featuring environmental protection, high efficiency, and low maintenance, but with relatively high initial investment costs.
The anaerobic fermentation principle of traditional septic tanks (such as primary and secondary compartment designs) is less commonly applied in mobile toilets due to space limitations and the need for immediate cleaning and transportation.
