Upgrading from batch to continuous flow process for the pyrolysis of sugarcane bagasse: Structural characterization of the biochars produced.

The waste from agriculture can be used for biochar production by the pyrolysis process. The present work aimed was to produce sugarcane bagasse biochars using different temperatures and processes (batch and pilot-scale continuous flow). The samples were characterized by FTIR, functional group pKa, elemental analysis, zeta potential, Raman spectroscopy, EPR, and SEM. The FTIR spectra showed bands around 1400-1650 cm-1 corresponded to vibrations of CC bonds and pKa revealed the presence of carboxylic acids (pKa ≤5) and lactones (pKa ~5-9). The elemental analyses (H/C ~ 0.31) and Raman spectra (ID/IG ~ 0.55) confirmed greater carbonization and less structural disorder of the material produced using the continuous flow process. SEM images showed that the biochar morphologies were similar to that of the precursor biomass, with the formation of pores. The continuous flow process is a promising technique for the production of biochars with high carbon contents and aromatic structures, as well as lower defect degrees, compared to biochars produced using a batch process.

Toxicity of the sawdust used for phosphorus recovery in a eutrophic reservoir: experiments with Lactuca sativa and Allium cepa.

Eutrophication is one of the environmental problems arising from the increase of essential nutrient concentrations, mainly phosphorus and nitrogen. In contrast to excess phosphorus, the depletion of phosphate rock deposits used for the production of fertilizers compromises the food supply. Therefore, the development of technologies that propose the recovery of the phosphorus contained in eutrophic environments for its later use for agricultural fertilization purposes is very important to ensure global food security. This work aimed to evaluate the toxic potential of the sawdust (biosorbent previously used for phosphorus adsorption) in order to enable its application in agriculture. For this, toxicity experiments with Lactuca sativa (lettuce) and Allium cepa (onion) seeds were performed. The phytotoxic potential was assessed by means of the seed germination index and physiological parameters such as radicle and hypocotyl growth. Cytotoxicity, genotoxicity, and mutagenicity tests were also performed on onion seeds. From statistical tests, it was possible to affirm that the sawdust did not promote inhibition of seed germination and radicle and hypocotyl growth. No genotoxicity, cytotoxicity and, mutagenicity were observed, which allowed to state that the sawdust is not toxic to the onion species, which reinforces the possibility of application of the biosorbent for soil fertilization purposes. Therefore, the use of sawdust for phosphorus biosorption with the subsequent agricultural application is promising and quite important from a global food security point of view.

Remediation of Eutrophic Aquatic Ecosystems: Evaluation of Phosphorus Adsorption by Sawdust.

A wide range of anthropogenic activities have caused various problems to the aquatic environment, leading to economic, social, and environmental losses. The use of materials for the recovery of water quality is very important due to the water scarcity scenario present in different parts of the world. The use of sawdust as an organic adsorbent for P removal in eutrophic environments attempts to address both water quality preservation and possible application of the organic adsorbent as fertilizer for agricultural practices. This use will result in important contributions to the water and food security. In this work, we performed laboratory experiments to study P adsorption and to evaluate possible adsorption of metals and emerging contaminants by sawdust. The experiments were carried out in 36 microcosms (glass jars), using 50% of the flasks as treatments (containing bags with sawdust) and the rest of the flasks as control (water and sediment without sawdust). For future application of sawdust as a fertilizer it is important to be aware of the presence of possible pathogenic microorganisms, thus the presence of helminth eggs was determined in the sawdust. The results showed the tendency of P adsorption by the biosorbent; maximum adsorption occurred at 214 d (41 µg P g-1 ), after the P desorption occurred. No helminth eggs or emerging contaminants and toxic metal were detected in the sawdust after its use as biosorbent, providing an important subsidy regarding the use of the biosorbent as soil fertilizer. Integr Environ Assess Manag 2019;00:1-12. © 2019 SETAC.

Multivariate analyses of the effect of an urban wastewater treatment plant on spatial and temporal variation of water quality and nutrient distribution of a tropical mid-order river.

Freshwater resources are increasingly scarce due to human activities, and the understanding of water quality variations at different spatial and temporal scales is necessary for adequate management. Here, we analyze the hypotheses that (1) the presence of a wastewater treatment plant (WWTP) and (2) a polluted tributary that drains downstream from the WWTP change the spatial patterns of physicochemical variables (pH, turbidity, dissolved oxygen, and electrical conductivity) and nutrient concentrations (reactive soluble phosphorus, total phosphorus, nitrogen series, total nitrogen, and total dissolved carbon) along a mid-order river in SE Brazil and that these effects depend on rainfall regime. Six study sites were sampled along almost 4 years to evaluate the impacts of human activities, including sites upstream (1-3) and downstream (5-6) from the WWTP. The impacts were observed presenting an increasing trend from the source (site 1) towards Água Quente stream (site 4, the polluted tributary), with signs of attenuation at site 5 (downstream from both WWTP and site 4) and the river mouth (site 6). Input of nutrients by rural and urban runoff was observed mainly at sites 2 and 3, respectively. At sites 4 and 5, the inputs of both untreated and treated wastewaters increased nutrient concentrations and changed physicochemical variables, with significant impacts to Monjolinho River. Seasonal variations in the measured values were also observed, in agreement with the pluviometric indexes of the region. Univariate analyses suggested no effect of the WWTP for most variables, with continued impacts at sites downstream, but non-parametric multivariate analysis indicated that these sites were recovering to chemical characteristics similar to upstream sites, apparently due to autodepuration. Therefore, multivariate methods that allow rigorous tests of multifactor hypotheses can greatly contribute to determine effects of both point and non-point sources in river systems, thus contributing to freshwater monitoring and management.

Biosorbent, a promising material for remediation of eutrophic environments: studies in microcosm.

Eutrophication is considered a global environmental problem that causes economic and biodiversity loss. Together with excess phosphorus in some aquatic environments, there is the depletion of phosphate rock deposits, which can directly affect fertilizer production and therefore global food security. Thus, the present work aimed to study a new remediation technique for eutrophic environments that enables the recovery of these environments through phosphorus adsorption in sawdust, creating the possibility to apply the phosphorus-enriched material as an agricultural fertilizer. The study was conducted in 36 microcosm flasks with water and sediment samples from a eutrophic reservoir in Ibirité/MG. The experiment was carried out using 18 control flasks and 18 others as treatment, consisting of water and eutrophic environment sediment and, additionally, two bags, containing 10 g of sawdust in each bag. The phosphorus adsorption on sawdust was more intense after 49 days of immersion in the microcosm, and reductions of 90% in the concentration of reactive soluble phosphorus were observed in the water column of the microcosm treatment at 159 days of the experiment. Based on the results, it can be concluded that, although the phosphorus concentration adsorbed on sawdust (16.2 µg g-1) is considered low, the use of the biosorbent is a particularly promising technique for remediation of eutrophic environments, as well as the possible reuse of the adsorbed phosphorus as a fertilizer in agriculture.

Off-line TMAH-GC/MS and NMR characterization of humic substances extracted from river sediments of northwestern São Paulo under different soil uses.

Humic substances (HS) vary according to the physical and chemical factors present in the environment. Thus, the characterization of HS is very important because it improves the understanding of the groups that comprise the chemical structure. Sediment HS were extracted from four locations representative of sugar cane cultivation, pasture, urban area and the impoundment of the Água Vermelha Hydroelectric Power Plant. Characterization using nuclear magnetic resonance (NMR) allowed us to infer that the HS from an area predominantly characterized by sugar cane cultivation (41.9%) and a typical rural area (35.0%) showed the highest aromaticity percentage. Using the off-line TMAH-thermochemolysis-GC-MS, we inferred that the HS of a typical rural area had a structure rich in plant waxes, plant biopolyester and a large amount of fatty acid methyl ester, which are related to the large amount of humic acid in the structure. The HS samples from the sugar cane cultivation area and the impoundment receiving all of the pollution load from the Turvo/Grande Hydrographic Basin (Bacia Hidrográfica do Turvo/Grande-BHTG) contained contributions from compounds rich in lipids and fatty acid methyl esters, highlighting the presence of the breakdown of petroleum-derived hydrocarbons in the area receiving the entire pollution load. We conclude that the HS extracted from the sediments of the Preto, Turvo and Grande rivers showed well-defined characteristics that varied depending on soil use and occupation, especially the HS extracted from sediments sampled in areas typically planted with sugar cane and rural areas, whose structures contained more aromatic groups.