Biogas generation: turning waste into three valuable products
In the vicinity of Lake Lucerne, the largest biogas plant in Switzerland has been converting slurry, manure and green waste into biogas since 2008. Even the digestate waste is valuable and after it has been treated is used as fertiliser and industrial water.
Waste management of a different kind
The SwissFarmerPower Inwil AG plant generates up to 1.9 million m³ of biogas a year. This renewable energy source is so appealing because it even puts waste to good use. What is left over is known as "biogas slurry", which is first separated into its solid and liquid parts with a flocculant. The solids are used as fertiliser and the liquid is further cleaned: first, ultrafiltration removes the fine suspended matter, then a reverse osmosis system treats the water. In preparation for this step, sulfuric acid is used to regulate the pH and antiscalant keeps the reverse osmosis membrane permeable. The treated water can now be fed into the clarification plant or be used immediately as industrial or washing water. The system for digestate treatment was supplied by the Gelsenkirchen company A3 Water Solutions GmbH – in which ProMinent technology is used.
- Biogas plant in Inwil, Switzerland: generation of around 2 million m³ biogas per year from green waste and biomass from agriculture
- Treatment of digestate with flocculants, filtrations and reverse osmosis
- Polymer preparation station: production of flocculant for the separation of liquid and solid components
- Solenoid diaphragm metering pump gamma/ L: metering of antiscalant prevents salt crystals forming on the reverse osmosis membrane
- Motor driven metering pump Vario C: metering of 78% sulfuric acid for pH regulation
From digestate slurry to clean water
Because the expert collaboration between A3 Water Solutions and ProMinent, and its reliable results were already known from previous projects, the choice was not a hard one to make. The flocculant comes from a fully automatic ProMinent polymer preparation station. This system needs only minimum maintenance and can be adapted to various changes in concentration. Before reverse osmosis, the user-friendly solenoid driven metering pump gamma/ L dispenses an antiscalant which protects the membrane of the reverse osmosis system against deposits. To reduce the pH value, the motor driven metering pump Vario C adds 78% sulfuric acid to the liquid. The chosen ProMinent products are easy and cost-effective to operate and offer rugged, chemical-resistant construction and precision metering.
Convenient project development, reliable result
- Safe separation of solids, reliable water treatment
- Fully automatic addition of polymers
- Reliable protection of the reverse osmosis system
- User- and maintenance-friendly system, cost-effective operation
- Quick on-site support