Recovery at the toilet

Phosphate can be recovered from the waste water by collecting urine separately in the toilet bowl. This method is known as decentralised sanitation. Special toilets have been designed for this purpose that separate urine from solid matter, which means that the urine is as undiluted as possible. The phosphates can be recovered by means of crystallisation.

Benefit

Decentralised sanitation has benefits that extend beyond the recovery of phosphate. Separate collection of urine also makes it easier to remove ammonia (nitrogen) from waste water. Approximately 85% of the nitrogen in waste water comes from urine. This process costs Dutch Water Boards a great deal of money. A large amount of energy is used at the sewage water treatment plants in order to separate ammonia from the waste water. When collecting urine separately the treatment plants will even produce a little more energy than they consume. In addition, a great deal of urine contains traces of medicines. Separate collection means that these traces are removed from the waste water immediately.

Disadvantage

A disadvantage of this method is that there are just as many sources as households. The construction of separate toilets and organisation of a special infrastructure costs a great deal of money. These objections can be refuted to a certain degree. For example, consider the collection of urine in places where large quantities are produced, such as in theatres, stadiums and hospitals. The urine is then transported to special purification installations. With this approach a large portion of the phosphate is still lost. Another objection is the resistance to separate waste collection. In the case of decentralised sanitation men must also urinate while seated. In addition, urine contains only half of what enters the sewer system. Solid matter also contains a large quantity of phosphate.