Background and Description

Nitrogen and phosphorus are the most relevant inorganic compounds to be considered when assessing and monitoring water quality. These compounds present in water bodies may come from diverse sources: synthesized fertilizers, farm wastes applied in agricultural uses, industrial effluents and more specifically, effluents coming from treating systems of waste waters.

Most of WWTP have a specific system for nitrogen removing, a system based on nitrification-denitrifying process; however, when speaking about phosphates, most of them are removed with the sludge after biological purification treatment has been applied.

One direct consequence of the pollution caused by these nutrients is its capacity to promote algal growing. The presence of nitrogen and phosphorus on water often causes water eutrophication through undesired algae proliferation. Nitrogen and phosphorus removal from waste water, or the transformation of ammonium into nitrates reduces the negative effects of spillage.

Eutrophication of water is followed by massive algal growing which inhabits rivers, lakes, estuaries and other aquatic ecosystems to which previously treated waters can be poured. This massive growing of algae can lead several species to disappear from this water bodies, due to the decrease in the oxygen rate; these species are often vital for life development in the ecosystem.

This fact creates several problems such as bad smells due to the decomposition of vegetal and animal products, colors and appearance modification in water and overall, contribution with a considerable decrease in the biological diversity which can negatively affect the development of the ecosystem.

There exists also health problems derived from the accumulation of phosphates in fresh water. The massive intake of products containing phosphates can result in health problems such as hiperphosphatemia or increase in inorganic phosphate amounts in blood, which is related to renal failure, because the kidney is in charge of phosphates removing from water.

Big amounts of phosphates and nitrates present on waste waters is one of the main causes of eutrophication which affects a wide number of natural waters, both fresh and marine (and therefore the aquatic ecosystem), thus negatively acting over human health. Therefore, it is necessary that waste water treatment fully remove phosphorus and nitrogen from waste water before these waters are transferred back into the environment.

Phosphates are present in bigger concentrations in Baltic countries. However, the European regions which have a higher presence of these compounds are France and Spain. Phosphates concentration in these countries is, in many cases, higher than 500 μg P/l. This implies a problem since critical concentrations for starting eutrophication process are situated among 100-200 μg P/l in water streams, and among 5 and 10 μg P/L in flat waters.

In view of the potential hazard for surface water, EU91/271/CEE Directive specifies a minimum 80% reduction of phosphates in WWTP. Therefore, the aim of these entities should be minimizing as much as possible the concentration of phosphates poured to water, maximizing the percentage reduction.

Most phosphates treated in WWTP come from urban and industrial effluents, mainly fertilizers, pharmaceutical industries, human and animal excretions and cleaning agents. There exists ways to remove these compounds through biological and chemical treatments. Biological treatments reduce phosphates concentration in treated water by removing sludge. Chemical treatment consists of adding compounds able to react with water, obtaining this way an easily removable precipitate from waste water. On the other hand, not all WWTP in the EU are well equipped with the appropriate technology to develop this task.

This project will enable the development of a technology easily implementable and low-cost for phosphates removal, which will enhance the efficiency in eliminating phosphates.