Nitrogen transformation in shallow tertiary lagoons: nitrogen fractions identification in sedimented solids (sludge) and suspended solids present in lagoons

• Grant number: 13/24297-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2013
• End date: August 31, 2014
• Field of knowledge: Engineering - Sanitary Engineering - Environmental Sanitation
• Agreement: SABESP
• Principal Investigator: Adolpho José Melfi
• Grantee: José Roberto Scalfi Junior
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Company: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALQ)

Abstract

Stabilization ponds are natural systems that require little or no mechanization for treating residuary water. Conventional facultative ponds present a major deficiency in the removal of ammoniac nitrogen, serving this nitrogen form as nutrient for the growth of algae and macrophytes. The uncontrolled growth of these organisms will cause the eutrophication of rivers and lakes with undesired environmental impact, and, depending on the use of the water from the recipient bodies, may lead to public health issues. The current residuary water treatment technologies, such as the activated sludge to remove nutrients, are too costly for the developing regions and the ponds are known for their capacity to achieve a significant organic and pathogenic pollutant removal rate. However, nitrogen removal has not been thoroughly studied yet. The stabilization ponds are not considered an alternative technique to remove nitrogen. However, recent studies intended to assess the effect of depth in tertiary ponds show have shown that nitrogen can be reduced to concentration levels below 5 mg/L by using 50-cm deep tertiary ponds and 10-day hydraulic detention periods. Some authors argue that organic nitrogen sedimentation is the prevailing nitrogen removal mechanism in facultative ponds. There are disagreements regarding the way nitrogen is removed, though. There is a removal model, with good correlation to the experimental data, which is based on the assumption that volatilization is the main nitrogen removal mechanism. Some authors report that quantifying and knowing the nitrogen transformation routes is important for the correct dimensioning of ponds. (AU)