Dynamics of nitrate degradation along an alternative latrine improved by a sawdust permeable reactive barrier (PRB) installed in an irregular settlement in the municipality of Sao Paulo (Brazil)

Autor(es)

Suhogusoff, Alexandra Vieira ^[1] ; Hirata, Ricardo ^[1] ; Aravena, Ramon ^[2] ; Robertson, William D. ^[2] ; Ferrari, Luiz Carlos K. M. ^[1] ; Stimson, Jesse ^[2] ; Blowes, David W. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, CEPAS USP Ctr Pesquisa Aguas Subterraneas, Inst Geociencias, BR-05508080 Sao Paulo, SP - Brazil

^[2] Univ Waterloo, Dept Earth & Environm Sci, Waterloo, ON N2L 3G1 - Canada

• Tipo de documento: Artigo Científico
• Fonte: ECOLOGICAL ENGINEERING; v. 138, p. 310-322, NOV 2019.
• Citações Web of Science: 0

Resumo

Nutrients, like nitrate and phosphate, and pathogens are the primary contaminants released into groundwater by on-site sanitation systems, which are an effluent disposal outcome for regions not covered by sanitation infrastructure, as periurban communities in developing countries. As appropriate setback distances between pit latrines and supply wells often cannot be met to avoid groundwater contamination, especially in a densely-populated situation, efficient, low-cost and accessible technologies are extremely necessary to protect water resources and surpass critical and persistent public health problems. This paper presents 1-year field-testing of an alternative latrine (AL) that incorporates two waste materials as permeable reactive barriers (PRB) in an irregular settlement at the municipality of Sao Paulo (Brazil). Basic oxygen furnace (BOF) slag in contact with wastewater effluent increases its pH level, which causes pathogens inactivation and phosphate adsorption. Sawdust under water saturation creates reducing conditions that encourage the growth of denitrifying bacteria that remove nitrate. A control latrine (CL) was constructed 90 m apart from AL with similar hydraulic characteristics and nonreactive materials for hydrochemical comparison. It was evident for AL the formation of well-defined nitrification and denitrification reaction zones, whereas CL overall presented nitrogen in its ammoniacal form, with incipient nitrate production at CL bottom, indicating that nitrification is probably boosted below that. BOF slag had attenuated microorganisms and phosphate almost completely, but nitrate removal average efficiency was 42%. The high pH effluent generated in BOF media may have also affected in the short-term the denitrifying bacteria in sawdust barrier 1 m below. The inverted position of the reactive barriers, i.e., sawdust PRB overlying BOF slag PRB, should be a more suitable design to achieve nitrate and pathogens removal. This kind of sanitation solution employing cheap and accessible waste materials have never been applied in the design proposed in this paper and also was a novelty for Brazilian context, proving to be a suitable technology to meet local needs. (AU)

• Processo FAPESP: 05/00315-5 - MINISIS: um método para avaliação e redução de impactos nos recursos hídricos causados por sistemas de saneamento in situ
• Beneficiário: Ricardo César Aoki Hirata
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 04/03484-0 - Minimização de impactos nos recursos hídricos causados por sistemas de saneamento in situ: estudo piloto em Parelheiros - São Paulo (SP)
• Beneficiário: Alexandra Vieira Suhogusoff
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 06/06562-7 - Implantacao de barreiras permeaveis reativas com capacidade de degradacao de microorganismos em aguas subterraneas.
• Beneficiário: Marcus Sangiorge Ucci
• Modalidade de apoio: Bolsas no Brasil - Iniciação Científica