How PAUL works
Drinking water through gravity.
PAUL stands for Portable Aqua Unit for Lifesaving and is a gravity-driven water treatment system. Inside, a membrane module retains turbidity, particles, as well as bacteria and viruses from untreated water.
Filtration with very low pressure
The principle is simple: raw water is poured in at the top and passes through the membrane module solely by gravity, using very low pressure. During this process, PAUL retains turbidity, particles, and pathogens. Clean water is collected inside and can be tapped via the outlet hose.
PAUL operates using ultrafiltration at very low pressure. This pressure is generated solely by the weight of the water inside PAUL, up to a maximum of approximately 0.08 bar. As a result, the system requires no electricity, pumps, or chemical additives.
1
Raw water is poured in
2
Gravity creates pressure
3
Membrane retains particles and pathogens
4
Filtered water can be tapped and collected
How the membrane module works
At the core of PAUL is a membrane module with 50 membrane sheets and a total of 100 membranes. Each sheet carries two membranes. The filtered water is collected inside and directed into a collection channel.
The membrane has a typical pore size of 35 to 100 nanometers. Pores of this size are extremely fine—100 nanometers correspond to roughly one thousandth of the diameter of a human hair.
During filtration, suspended solids, particles, as well as bacteria and viruses are retained on the membrane. Over time, a filtration layer forms, which further enhances the filtration process.
PAUL is not suitable for saltwater or chemically contaminated water.
Suitable
Surface water such as rivers, streams, lakes
Well water
Rainwater
Not suitable
Saltwater
Chemically contaminated water
Technical facts at a glance
Pressure principle
Gravity-driven, max. approx. 0.08 bar
Filtration
Ultrafiltration with flat-sheet membranes
Membrane module
50 membrane sheets
Pore size
35–100 nm
Membrane area
Approx. 10 m²
Capacity
Minimum 1,200 liters per day
In practice: 2,000 to 6,000 liters per day have been reported
Lifetime
10+ years
Pathogen reduction
Over 99.99%* of viruses and bacteria
Spare parts
No spare parts required
*As tested by Fresenius Institute and German Federal Environmental Agency
Robust in Operation
PAUL is designed for simple and robust use. The system operates with minimal technology, requires no electricity, and does not need chemical additives. Ongoing effort is also minimal: the membrane is designed for a service life of more than ten years, and no spare parts are required.
A technical advantage lies in the system design: deposits are carried downward by gravity. This helps keep the membrane functional and prevents clogging.
Developed at the University of Kassel
PAUL was developed at the Department of Urban Water Management at the University of Kassel and has been scientifically tested. The technology is based on the work of Prof. Dr.-Ing. Franz-Bernd Frechen and combines technical robustness with deliberately simple application in the field.
Learn more about PAUL
Want to know if PAUL is suitable for your project?
We are happy to advise you on water sources, operating conditions, and the right product variant.