In this study, removal of organic matter and nitrogen from a cattle slaughterhouse wastewater was investigated in a two‐stage anoxic–aerobic biological system, followed by UV‐C disinfection. Ecotoxicity of the raw, biotreated, and disinfected wastewater against the microalgae Scenedesmus sp. was evaluated in short‐term tests, while the potential of the microalgae as a nutrient removal step was addressed in long‐term experiments. Throughout 5 operational phases, the biological system was subjected to gradual reduction of the hydraulic retention time (8–1.5 day), increasing the organic (0.21–1.11 kgCOD·m−3·day−1) and nitrogen (0.05–0.28 kgN·m−3· day−1) loading rates. COD and total ammoniacal nitrogen (TAN) removal ranged within 83%–97% and 83%–99%, respectively. While providing alkalinity source, effluent TAN concentrations were below 5 mg·L‐1. Nitrate was the main nitrification product, while nitrite levels remained low (<1 mgN·L‐1). Upon supplementation of external COD as ethanol, total nitrogen removal reached up to 90% at the highest load (0.28 kgN·m−3·day−1). After UV‐C treatment, 3‐log reduction of total coliforms was attained. The 96‐hr ecotoxicity tests showed that all non‐diluted samples tested (raw, biologically treated and UV‐C irradiated wastewater) were toxic to microalgae. Nevertheless, these organisms were able to acclimate and grow under the imposed conditions, allowing to achieve nitrogen and phosphorous removal up to 99.1% and 43.0%, respectively.
Practitioner points
The treatment of a slaughterhouse wastewater in an anoxic–aerobic biological system followed by a UV‐C disinfection step was assessed.
The pre‐denitrification system showed efficient simultaneous removal of organic matter and nitrogen from the wastewater under increasing applied loads.
UV‐C disinfection worked effectively in reducing coliforms from the biotreated effluent, boosting the performance of microalgae on nutrients removal.
Despite the toxicity to microalgae, they were capable to acclimate to the aqueous matrices tested, reducing efficiently the nutrients content.
The combined stages of treatment presented great capacity for depleting up to 97% COD, 99% nitrogen, and 43% phosphorous.
Humic substances are the main constituents of natural organic matter, found in both aquatic and terrestrial environments. Humic substances are a complex, dispersed, and heterogeneous mixture of various organic compounds synthesized from organic matter residues, decomposed by microorganisms. Most scientists indicate that humic substances are as a supramolecular association of small heterogeneous molecules stabilized by weak intermolecular bonds. When these substances are presented in water intended for drinking or industrial use, it can have a significant impact on the treatability of this water and on the success of chemical disinfection processes, due to possible formation of organic compounds harmful to human health. Moreover, the humic substances can be used of several ways such as fertilizer to help in the development of plants, to improve soil erosion and to removal of organic compounds and metals from soils and waters. In addition, humic substances suggest an important role in mitigating areas degraded by the phytoremediation technique. The purpose of chapter is to provide an overview of humic substances and to discuss their concepts, chemical characteristics, ecological effects and technological applications for soils and aquatic systems.
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A conversão de áreas de floresta em áreas de pastagem levanta discussões sobre as possíveis mudanças que esse ato pode provocar no clima, tanto regional, quanto global. Dessa forma, o presente estudo buscou analisar os componentes do balanço de energia nos quatro períodos do ano de 2010 em uma área de pastagem localizada no sudoeste da Amazônia. Os dados foram coletados por instrumentos instalados em uma torre meteorológica do Programa LBA e calculados a partir do método de covariância de vórtices turbulentos. Para os períodos úmido, úmido-seco, seco e seco-úmido a média em
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