Composição química da matéria orgânica de lodos de esgoto

Abstract

RESUMOLodos de esgoto podem ser reciclados no solo agrícola como fonte de nutrientes para as plantas e visando o aumento no teor de matéria orgânica. O objetivo do presente trabalho foi caracterizar a fração orgânica de lodos de esgoto (teores totais, orgânicos e inorgânicos de carbono, nitrogênio e fósforo; concentrações de carbono solúvel em água, açúcares solúveis, proteína bruta, lipídeos, hemicelulose, celulose, lignina, fenóis e taninos totais), de modo a auxiliar no planejamento de seu uso na agricultura. Foram utilizados cinco tipos de lodos de esgoto com diferenças quanto às etapas posteriores de condicionamento químico e/ou tratamento complementar para desidratação, sendo três provenientes de processo anaeróbio: cal e cloreto férrico, desidratado mecanicamente (LAC); polímero sintético e desidratado mecanicamente (LAP); polímero sintético e desidratado termicamente (LAS), e dois de processo aeróbio de digestão: condicionamento com polímero sintético e secagem em leitos (LLP); LLP após processo de compostagem em pilhas aeradas em mistura com bagaço de cana-de-açúcar e restos de poda urbana, composto de lodo (CL). O condicionamento com polímero e secagem térmica conservou mais a matéria orgânica do resíduo, o que foi evidenciado pela presença de maiores teores de compostos orgânicos facilmente degradáveis, bem como de carbono (337,24 g kg -1 ), nitrogênio (39,02 g kg -1 ) e fósforo (2,93 g kg -1 ) no compartimento orgânico. Em todos os lodos houve expressiva participação do conteúdo protéico na matéria orgânica, que foi de aproximadamente 43, 42, 28 e 25 % para os lodos de esgoto LAC, LAP, LAS, LLP e CL, respectivamente. Palavras-chave: biossólidos, compostos orgânicos, fertilizante orgânicoChemical composition of sewage sludge organic matter ABSTRACT Sewage sludge can be recycled in agricultural soil as a source of plant nutrients and in order to increase the organic matter content. The objective of this study was to characterize the organic fraction of sewage sludge (contents of carbon, nitrogen and total organic and inorganic phosphorus; concentrations of protein, fat, fiber, phenol and tannin) in order to assist in planning their use in agriculture. Five types of sewage sludge with differences were used for the later stages of chemical conditioning and / or complementary treatment for dehydration, three from anaerobic process: lime and ferric chloride, mechanically dehydrated (LAC); synthetic polymer and dehydrated mechanically (LAP); synthetic polymer and thermally dehydrated (LAS), and two aerobic digestion process: etching synthetic polymers with drying beds (LLP); LLP after the composting process in aerated piles mixed with bagasse from sugar and urban pruning debris, sludge compost (CL). The conditioning polymer and heat drying the organic matter retained in the residue, which was evidenced by the presence of higher concentrations of readily degradable organic compounds and carbon (337.24 g kg -1 ), nitrogen (39.02 g kg -1 ) and phosphorus (2.93 g kg -1 ) in the organic compartment. In all sludg...

Characterization of sewage sludge generated in Rio de Janeiro, Brazil, and perspectives for agricultural recycling

“…Taking into account that sugarcane is the most cultivated agricultural crop in Rio de Janeiro, corresponding to approximately 49% of the total agricultural area cultivated in the state (EMATER, 2014); sludge reuse for fertilizing this crop can be one of the strategic alternatives for the state's agricultural sector. P contents in the sludge lots analyzed ranged from 5.22 to 17.23 g kg , values close to those observed in other studies (CARVALHO et al, 2015;CONSUEGRA et al, 2015;TRANNIN, 2015;SAMPAIO, 2010). Sludge lots from STS Ilha do Governador presented the lowest P contents whereas STS Sarapuí presented the highest contents of this nutrient.…”

“…The analyzed sludge presented K contents varying from 1.82 to 5.00 g kg Ca was found in contents ranging from 1.35 to 18.51 g kg −1 of sludge on a dry basis. In the studied STSs, liming treatment is not adopted for sludge cleaning, justifying these lower Ca contents in the sludge when compared to other studies (CARVALHO et al, 2015;CONSUEGRA et al, 2015;NASCIMENTO, 2016). Sludge from lot VI (STS Ilha do Governador), analyzed in January 2016, presented higher Ca content than the other samples, which may be the result of some punctual source of this nutrient in the drainage basin.…”

“…Carvalho et al (2015), analyzing five different sludge from STSs in São Paulo, Brazil, found similar N contents, which ranged from 17.40 to 42.63 g kg…”

“…Those of Aguilera et al (2007) who characterized the sludge from three STSs in Chile; MTSHALI et al (2014) who analyzed the sludge from seven STSs in Swaziland (Southern Africa); and Carvalho et al (2015) who analyzed five different sludge from two STSs in São Paulo State, Brazil. All of these studies and the current one reported high contents of organic matter and nutrients in sewage sludge, mainly N and P. Sampaio , P from 6 to 30 g kg…”

“…In the sewage sludge, the largest N portion is in an organic form and, therefore, it is readily available for plants only after organic matter degradation (CARVALHO et al, 2015;NASCIMENTO, 2016). This characteristic causes the N present in sewage sludge to be released slowly into the system, which may be favorable when compared to chemical fertilizers.…”