Due to their defined pore size (<0.1μm), the membranes used for wastewater treatment physically separate the smallest particles up to colloids from liquids. Membranes retains substances without physically or chemically changing. This prevents hazardous substances from being formed in the first place. Flat membranes made of organic polymers which, in combination with sophisticated filter design, effectively prevent filter from being clogged by hair, fibers or other unhygienic coarse substances.