Skip to content

Recovery of phosphorus

Current situation

By 2029 at the latest the legal requirements will require that sewage sludge no longer can be used as fertilizer. The contained phosphorus has to be recovered. Various methods already exist for the recovery of phosphorus.

The process for phosphorus recovery newly developed by PH2 can be integrated both –  in the sewage treatment plant and in the sewage sludge recycling. It is particularly characterized by a high recovery performance before energetic/ thermal use. In this way the subsequent process can be energetically optimized without losses in recovery.

PH2 module for phosphorus recovery

The innovative PH2 process is able to convert electrochemically and organically bound phosphorus into phosphate in the same step without dissolving heavy metals.

The precipitated product has significantly lower problem substance loads than actually mined phosphorus.

IMG_6682.freigestellt (5)-min

The recovered phosphorus is very readily available to plants and is not soluble in water.

The recovery rate from the wet sewage sludge is approximately 90%. In a ressource-saving cycle process for phosphorus recovery the used additives can be removed and recycled.
There are no harmful waste water or exhaust air streams that could pollute the environment.

The combination of sewage sludge drying and phosphorus separation not only increases the efficiency of both parts of the plant but also significantly increases the calorific value of the dried sludge.

Your questions about  RECOVERY OF PHOSPHORUS

Why phosphorus recovery?

Phosphorus is needed by all plants for growth. That is why phosphorus is an indispensable fertilizer in agriculture. More than 90% of the phosphorus mined worldwide comes from deposits in Morocco, China and the USA. Morocco contains almost 75% of the known phosphorus. In Germany phosphorus must therefore be obtained from the available sources. This is mainly sewage sludge from the sewage treatment plants and the digestate from the biogas plants. See also: Commodity Management Profiles – Phosphate (2014) (

How does phosphorus get into the sewage sludge?

Because of its reactivity phosphorus is only present in nature as a compound with substances as phosphate or phosphoric acid. Phosphorus is needed by plants as a nutrient for growth and is absorbed by humans and animals when ingesting plant food. Phosphorus enters the sewage sludge as part of the faeces. Until a few years ago phosphates were still present in detergents and dishwashing detergents. Since 2017 this has only been permitted for commercial means.

Why should phosphorus be recovered from sewage sludge?

The globally available deposits of phosphorus from opencast mining / mining sources will last for about 100 years and the mining regions are partly in politically unstable or not reliable regions. Therefore it makes sense to recover the already here existing phosphorus e.g. in sewage sludge. Phosphorus is also contained as phosphoric acid in seawater in a concentration of about 50 μg/l. From this it can already be seen that we should conserve the resource phosphorus for future generations and make a contribution to the sustainable management of our planet by recovering it. The PH2 plant for phosphorus recovery is an environmentally friendly and energy-saving contribution to phosphorus recovery. The plant can separate 90% of the phosphorus from the sewage sludge without using environmentally harmful substances.

What happens to the pollutants produced during the combustion of sewage sludge?

During the combustion of sewage sludge different pollutants are produced depending on the combustion temperature. The pollutants are collected and reduced with filters located in the exhaust system or the residues are disposed in a landfill. However it makes more sense to process the sewage sludge with a plant from PH2 Technology GmbH and to extract new raw materials from the sewage sludge.

Phosphorus recycling: what needs to be considered?

If the phosphorus content of a sewage sludge is higher than 2% of the dry residue then phosphorus recovery must take place from 2029 (sewage treatment plants from 100,000 PE) or 2032 (sewage treatment plants from 50,000 PE) depending on the size of the sewage treatment plant. From 2023 sewage treatment plants are forced to develop a concept for phosphorus recovery.

What is the legal basis for phosphorus recovery?

The obligation to recover phosphorus is laid down in the Sewage Sludge Ordinance.