Phosphorus recovery from sewage treatment plants through sorption and coagulation-flocculation

Author(s)

Camille Nunes Leite

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2022-03-09

Examining board members

Paulo Sergio Pavinato; Marcos Yassuo Kamogawa; Leônidas Carrijo Azevedo Melo

• Advisor: Paulo Sergio Pavinato

Abstract

In recent decades, a considerable advance in new technological alternatives for phosphorus (P) recovery via effluents and sewage sludge has been reached around the world, some of which are already in the stage of implementation on a full scale. However, the false idea that these sources are tailings, variations in the requirements of each country and state, as well as the high compositional variability of effluents, structure, and methodology of treatment plants (ETEs) make their adoption impossible in the absence of a punctual study. In Brazil, data is still lacking and very little is done about nutrient recovery, treatments are still inefficient, with treated water still rich in nutrients and sewage sludge still destined for landfills. Based on that, this research aimed to study two distinct mechanisms, adsorption, and coagulation-flocculation, in the improvement of water treatment at ETE Bela Vista in the city of Piracicaba/SP, regarding the recovery parameters of total P and total nitrogen (N). Therefore, in coagulation-flocculation, the use of inorganic coagulant aluminium sulfate [Al2(SO4)3] and different organic coagulants based on cationic tannins (black wattle extracts) in doses of 5 200 ppm were studied. In the adsorption process, the adsorbents obtained from impregnation and heat treatment of sugarcane bagasse with magnesium chloride and zeolite with calcium chloride (BCMg and ZCa, respectively) were produced and characterized, at mass of 0. 5 7 g L-1 of effluent were studied. Based on the results, coagulation-flocculation using doses between 25 - 150 ppm of Al2(SO4)3 and anionic polyelectrolyte were able to reduce the total P load by more than 85%, accelerating the decantation process and reducing the parameters controls such as COD (10 31%) and N-Kjeldahl (25 48%). With the use of 3 g L-1 of the BCMg adsorbent, it was possible to reach values of total P in the treated effluent in the order of 0.03 mg P L-1 and 10.6 mg N L-1 of N-Kjeldahl, which represents more of 85% and 24% removal, respectively. In the case of using 5 g L-1 of ZCa, the reductions in total P and N-Kjeldahl were greater than 65% (final concentration of 0.09 mg P L-1) and 45% (7.7 mg N L-1), respectively. As these nutrients are usually destined for sludge, the use of both processes represents enrichment of the final sludge, which can have significant effects on nutrient recycling through the use of sludge in agriculture. Therefore, the coagulation-flocculation and adsorption processes are efficiently capable of reducing total P and N-Kjeldahl, returning even cleaner water to the Piracicaba River and enriching the sludge. The feasibility and efficiency of applying these methods on a full scale, as well as the study of the effects of this sludge enrichment in recycling are still necessary. (AU)

• FAPESP's process: 20/09191-7 - Nutrient recovery in sewage treatment plants through adsorption and coagulation-flocculation
• Grantee: Camille Nunes Leite
• Support Opportunities: Scholarships in Brazil - Master