Extraction of nitrogen and phosphorus in the form of struvite from wastewater with high nutrients concentration

Summary

The world reserves of phosphate ore total about 7000 mln tons among them 40 mln tons are used annually in fertilizer production. It is estimated that this resource will be depleted by 2090. In this connection exploring alternative renewable phosphorus sources is a critical task; therefore much attention is paid to developing economical and technically available methods of phosphorus extraction together with nitrogen from different wastewater types; one of the methods being nutrients precipitation in the form of struvite (MgNH₄PO₄·6H₂O). Studies of struvite production from wastewater and its use as a fertilizer have been carried out in many countries of the world. Process schemes of struvite extraction from municipal wastewater, steel making and tanning wastes, coking process effluents, solid waste landfill filtrate, livestock and dairy farm wastewater as well as from black wastewater in the process of its decentralized processing have been developed. Studying the use of struvite as a fertilizer has been carried out almost 20 years already. Generally the prospects of investing in the production of this product for the agricultural sector are not disputed. The practice of production and supply of struvite as a fertilizer has been fairly developed in Japan. The application of struvite does not result in the increase of heavy metal concentration in farm crops. Fast dissolving fertilizers are not efficient when used on pastures or in forests where fertilization is practiced every few years. In this context the use of slowly dissolving fertilizers including struvite is more reasonable.

Key words

wastewater , nitrogen , phosphorous , struvite , filtrate of solid waste landfills , phosphatic fertilizers

Process solutions to increase the efficiency of wastewater treatment with a low concentration of organic matter

Summary

Through the example of the Moscow wastewater treatment facilities, the ways of improving the efficiency of treatment of low-concentrated wastewater in terms of organic matter are considered: the acidification of raw sludge, addition of an external organic substrate, use of technologies independent of the concentration of organic substances. In the presence of refluxes containing nitrogen and phosphorus, the use of organic matter-independent technologies is promising to reduce the nitrogen and phosphorus load on the main biological treatment line. Process solutions that improve the efficiency of nitrogen and phosphorus removal from low-concentrated wastewater in terms of organic matter at the Liuberetsky and Kurianovsky treatment facilities are as follows: acidification of raw sludge to increase the concentration of readily available organic matter; local treatment of refluxes from the sludge treatment facilities to reduce the nitrogen and phosphorus load on the biological treatment using the Anammox process and obtaining a mineral fertilizer – struvite (magnesium ammonium phosphate). At the small-scale wastewater treatment facilities of New Moscow, the addition of yeast condensate as an additional organic matter provides for increasing the BOD₅/N_total ratio from 3.2 to 4.3, which under these conditions is sufficient for the successful denitrification and biological dephosphorization processes. This made it possible to ensure the standard level of removing nitrogen of nitrates and phosphorus of phosphates and, as a result, reduce the consumption of the chemical (ferric chloride).

Key words

wastewater treatment , removal of nitrogen and phosphorus , best available techniques , return flows , nutrients removal , struvite , Anammox technology , low concentration of organics in wastewater