"Why is phosphorus elimination an important contribution to water protection?"

Q: "Why is phosphorus elimination an important contribution to water protection?"

"An excess of nutrients (phosphorus, nitrogen) in water bodies (lakes, rivers, seas) leads to an increased and rapid growth of algae. Since algae also need sunlight for growth (photosynthesis), algae mainly stay in the exposed part of the water. The high density of algae then leads to less light penetrating to the plants growing further down. As a result, the entire biodiversity of the water body is disturbed or negatively affected. Some plants will gradually die off and be replaced by less sensitive species. When the excessively proliferating algae die off in large quantities and sink to the bottom of the water body, this biomass is broken down by bacteria using up oxygen. The strong oxygen consumption is then another negative effect, so that living organisms such as mussels and fish may die.\r\nThis whole process is called eutrophication and eutrophication is a worldwide problem. The cause of eutrophication is the excessive input of nutrients into water bodies. Input via untreated or insufficiently treated wastewater is one of several input pathways. Other input pathways are agriculture and industry.\r\nIn order to minimise nutrient inputs through wastewater, the concentration of phosphorus and nitrogen in treated wastewater must be as low as possible."

Phosphorus Elimination

Sustainable Use of our Waters

Municipal wastewater contains between 5 and 15 mg/l phosphorus. If phosphorus is not adequately removed during wastewater treatment, it ends up in the receiving waters. In lakes and rivers, phosphorus acts as a nutrient that generally promotes and accelerates plant growth, especially algae growth, which has a negative impact on water quality and thus on the biotic communities in the water body.

Reducing phosphorus inputs from municipal wastewater treatment plants is therefore a very important contribution to maintaining or achieving a good ecological status in flowing waters.

Three different processes are available for the elimination or reduction of phosphorus at municipal wastewater treatment plants, which are used either individually or in combination:

Biological phosphorus elimination
Chemical-physical processes
Flocculation filtration

HUBER Pile Cloth Media Filter RotaFilt® in operation

Phosphorous elimination by means of flocculation filtration

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Three Ways to Filter Phosphor

Biological phosphorus elimination

The Bio-P process, i.e. the increased biological phosphorus elimination, is based on a special process management in biological wastewater treatment. Through the targeted alternation between anaerobic and aerobic conditions, an increased uptake of phosphorus by certain bacteria is achieved.

Chemical-physical processes

Here, a precipitant (iron or aluminium salts) is added to the wastewater, which precipitates the phosphorus so that it can be separated with the sewage sludge.

Flocculation filtration

In addition to the aforementioned phosphorus elimination processes, a filter unit is installed in the outlet of the secondary clarifier. With the addition of precipitation and flocculation aids, very extensive phosphorus elimination can be achieved.

Flocculation

Flocculation Filtration

HUBER offers reliable and proven process technology for flocculation filtration, which ensures that the relevant phosphorus limits can be safely met.

Flocculation filtration with sand filter

The sand filter used is the HUBER Sandfilter CONTIFLOW®, which is a deep-bed type upflow filter that provides filter bed cleaning without interrupting the filtration process. The precipitant (e.g. FeCl₃ solution) is added into the feed line to the filter. Due to the fast reaction time of the precipitant with the ortho-phosphate, the filter bed of the sand filter can be used directly as reaction volume. The precipitated ortho-phosphate is then separated together with other solids in the sand filter and phosphorus concentrations of < 0.2 mg/l can be maintained in the outlet of the sand filter.

Flocculation filtration with cloth filter

The HUBER Pile Cloth Media Filter RotaFilt®, which consists of several rotatably arranged disc-shaped filter elements, is used as cloth filter. The wastewater with the added precipitant is passed through the filter system and the precipitated phosphate compounds, together with other solid particles still present, are reliably separated by the filter discs. Phosphorus concentrations of < 0.2 mg/l can be maintained in the outlet of the cloth filter.

img-application-phosphorus-elimination-sketches-01 — Flocculation filtration with sand filter or pile cloth media filter

Case Studies

HUBER Solutions in Operation

Phosphorus reduction with the HUBER RoDisc® Rotary Mesh Screen

A disc filter screen is a simple yet efficient solution which can be used to meet various specific requirements of phosphorus reduction.

Downloads

Customer Information and Documents

Brochure: Solutions for advanced wastewater treatment

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FAQ

Frequently Asked Questions

An excess of nutrients (phosphorus, nitrogen) in water bodies (lakes, rivers, seas) leads to an increased and rapid growth of algae. Since algae also need sunlight for growth (photosynthesis), algae mainly stay in the exposed part of the water. The high density of algae then leads to less light penetrating to the plants growing further down. As a result, the entire biodiversity of the water body is disturbed or negatively affected. Some plants will gradually die off and be replaced by less sensitive species. When the excessively proliferating algae die off in large quantities and sink to the bottom of the water body, this biomass is broken down by bacteria using up oxygen. The strong oxygen consumption is then another negative effect, so that living organisms such as mussels and fish may die.

This whole process is called eutrophication and eutrophication is a worldwide problem. The cause of eutrophication is the excessive input of nutrients into water bodies. Input via untreated or insufficiently treated wastewater is one of several input pathways. Other input pathways are agriculture and industry.

In order to minimise nutrient inputs through wastewater, the concentration of phosphorus and nitrogen in treated wastewater must be as low as possible.