Composition, fate, and transformation of extracellular polymers in wastewater and sludge treatment processes

Extracellular polymers are produced by microorganisms for protection and attachment. They can be loosely-bound (slime) or firmly attached (capsule) to the cell wall. In wastewater and sludge treatment, biopolymers have important roles in flocculation, sludge dewatering, metals removal, and reuse of treated wastewater. The characterization of biopolymers in treatment processes is incomplete, with most data coming from activated sludge. This research was designed to provide a comprehensive knowledge of the composition and fate of biopolymers in wastewater and sludge treatment processes. Three sets of samples were collected in nine locations at a full-scale wastewater treatment plant during a three month period. Capsule was extracted using a cation exchange resin, while slime were separated by centrifugation. Biopolymers were analyzed for carbohydrate, protein, RNA, DNA, humic acids, total organic carbon, trace metals, and molecular weight. Protein, carbohydrate, RNA, DNA, and humic acids were all constituents of biopolymers. Protein was the major compound in both capsule and slime. The inorganic fraction comprised 10 % to 20 % of the biopolymers’ weight. Molecules with sizes greater than 2.0 x 10⁶ were present in biopolymers. The capsule content of volatile suspended solids in digested sludge was 65 % of the capsule content of VSS in activated sludge. Statistical analysis suggested that the quantity of capsular biopolymer changed in different locations, but the composition remained the same. The hypothesis that the biopolymer contents of volatile suspended solids in digested sludge, primary, and secondary effluents were the same was not rejected. The equality hypothesis for biopolymer contents between activated sludge and secondary effluent VSS was rejected. Statistical analysis suggested that the quantity of capsular biopolymer changed in different locations, but the composition remained the same. The hypothesis that the biopolymer contents of volatile suspended solids in digested sludge, primary, and secondary effluents were the same was not rejected. The equality hypothesis for biopolymer contents between activated sludge and secondary effluent VSS was rejected. These results, together with the observation that digested sludge VSS contained less biopolymer than activated sludge VSS, suggest that particles from anaerobic digester were significantly present in effluents, or there was a preferential settling of particles holding more biopolymers in the sedimentation tanks. Mass balances showed production of capsular biopolymer constituents in the activated sludge process, and destruction during anaerobic digestion. Production and destruction varied in the ranges of 25 % to 40 %, and 60 % to 70 %, respectively. The contents of trace metals in capsular biopolymer from wastewater were higher than the metal contents at other locations in the plant. Trace metals associated with capsule represented less than 10 % of the metals measured in samples; in samples with low SS concentration, trace metals associated with slime reached 45 % of the metal contents in samples

The influence of cell detention time and endogenous decay on the stoichiometry reactions of biological processes in wastewater treatment : I - Chemoheterotrophic growth

No metabolismo quimioheterotrófico, um mesmo substrato orgânico é utilizado como fonte de energia e síntese celular. Este artigo apresenta uma metodologia que pode ser usada para calcular a estequiometria do metabolismo quimioheterotrófico considerando o tempo de detenção celular e o decaimento endógeno. O método se baseia em princípios da bioenergética e é útil para o desenvolvimento de balanços de massa em processos biológicos de tratamento de águas residuárias. Também serve para se estimar as necessidades de nutrientes, alcalinidade e aceptores de elétrons para as reações desejadas, assim como a biomassa formada e gases produzidos.In chemohetrotrophic metabolism, an organic substrate is used as energy and cell synthesis sources. This article presents a methodology that can be used to calculate the stoichiometry of chemoheterotrophic metabolism, considering solids detention time and endogenous decay. The method is based on bioenergetic principles, and is useful for mass balance calculations for biological processes used in wastewater treatment. It is also applied to estimate nutrients, alkalinity and electron acceptor requirements for the intended reactions, as well as biomass and gas production

Phosphorus removal in domestic wastewater treatment plant by calcined eggshell

Recovery of phosphorus (P) from wastewater is a topic of great interest. Besides being a non-renewable resource, P discharge in receiving waters can trigger algae blooms. The present study aimed to quantify the removal of P from two sites at a wastewater treatment plant using calcined eggshell (CES) as adsorbent. CES was prepared from raw shells calcined at 600 °C (CES600) and 800 °C (CES800). CES at 800 °C proved to be an efficient material for P removal. Efficiencies greater than 70% were achieved using CES800 concentrations of 0.1 g L 1 for synthetic sample, 0.3 g L 1 for preliminary treated wastewater and 20 g L 1 for supernatant from sludge anaerobic digester. The adsorption process was fast, occurring mostly in the first 30 min. Both Langmuir and Freundlich isotherms fitted the experimental data on adsorption. In kinetic experiments, a pseudo-second-order model fitted P adsorption from synthetic, preliminary effluent and digester supernatant. Thermogravimetric analysis showed a 54% eggshell mass loss at 800 °C. Calcination increased calcium and reduced carbon fractions in the eggshells, while increasing the surface area

Monitoring of pesticides in water supply systems : a comparative analysis between Ordinance no. 888/2021 and international directives

A presença de agrotóxicos na água para consumo humano é uma preocupação crescente no Brasil e no mundo. Procedimentos de vigilância e controle são necessários para garantir a água potável livre de traços de agrotóxicos. Os países desenvolvidos, em sua maioria, controlam regularmente os principais agrotóxicos. As diretivas internacionais planejam o monitoramento avaliando se já houve detecção na água, qual o comportamento ambiental dos ingredientes ativos e quais os riscos associados à saúde humana e ao meio ambiente. A frequência adotada em função destes critérios não é uniforme para os diferentes compostos. No Brasil, a Portaria n.º 888/2021 define uma periodicidade semestral para 40 agrotóxicos aplicada a todos os sistemas de abastecimento de água. O atendimento desta demanda é complexo considerando a logística precária e a falta de recursos em algumas regiões brasileiras. Cabe à vigilância sanitária dos municípios avaliar os planos de monitoramento dos operadores, que podem ser prejudicados pela falta de infraestrutura e carência de pessoal capacitado. Tendo em vista as questões abordadas, este artigo compara as exigências das práticas internacionais com as da Portaria nº 888/21 para o monitoramento de agrotóxicos, e destaca a necessidade de estabelecer procedimentos que otimizem as ações necessárias na elaboração de planos de monitoramento.The presence of pesticides in water for human consumption is a growing concern in Brazil and worldwide. Surveillance and control procedures are necessary to guarantee drinking water free of traces of pesticides. Most developed countries regularly control the main pesticides. International guidelines design monitoring plans by assessing whether the pesticides were already detected in water, what is the environmental behavior of the active ingredients, and what are the risks associated with human health and the environment. The frequency adopted according to these criteria is not uniform for the different compounds. In Brazil, Ordinance No. 888/2021 defines a six-monthly frequency for 40 pesticides applied to all water supply systems. Meeting this demand is complex considering the precarious logistics and lack of resources in some Brazilian regions. It is up to the health surveillance of the municipalities to evaluate the operators' monitoring plans, which can be hampered by the lack of infrastructure and of trained personnel. In view of the issues addressed, this article compares the requirements of international practices with those of Ordinance No. 888/21 for the monitoring of pesticides, highlighting the need to establish procedures that optimize the necessary actions in the preparation of monitoring plans

Removal of the odoriferous compounds geosmin and 2-methylisoborneol from drinking water by the processes of cascade aeration, air stripping and nanofiltration

Atividades humanas aceleram o processo natural de eutrofização das águas, favorecendo a floração de algas e cianobactérias. Estes organismos emitem os compostos 2-metilisoborneol (MIB) e geosmina, que conferem gosto e odor de mofo e terra à água. A presença destes compostos se estende à água potável uma vez que os processos convencionais de tratamento são insuficientes para removê-los. Esta pesquisa foi realizada com o objetivo de avaliar alternativas de processos de tratamento para a remoção de MIB e geosmina da água. Os processos estudados foram aeração em cascata, dessorção por ar e nanofiltração. Os resultados sugerem a possibilidade de remoção quase total de MIB e geosmina da água através do sistema de nanofiltração, enquanto que os processos baseados em aeração e dessorção foram relativamente ineficientes.Human activities accelerate the natural process of eutrophication, favouring the occurrence of algae and cyanobacterial blooms. These organisms emit the compounds 2-methylisoborneol (MIB) and geosmin, which confer earthy and moldy taste and odor to water. The presence of MIB and geosmin is extended to drinking water inasmuch they are not completely removed by the processes used in conventional treatment. This research was conducted to evaluate the capability of alternative treatment processes to remove MIB and geosmin from water. The processes studied were cascade aeration, air stripping, and nanofiltration. The results suggested that MIB and geosmin can be almost completely removed by nanofiltration, while the processes based on aeration and stripping were relatively inefficient

Characterization of dissolved organic matter in drinking water treatment processes using rapid fractionation

Matéria orgânica natural (MON) é uma complexa matriz de compostos orgânicos originados de fontes naturais que estão presentes em corpos hídricos. A MON é comprovada precursora de subprodutos da desinfecção (SPD), além de afetar processos de tratamento de água, tais como a coagulação, a desinfecção, a oxidação, a adsorção em carvão ativado e a filtração em membranas. Por essas razões, a redução da MON no tratamento de água para consumo humano é importante. Vários métodos são usados para caracterizar e quantificar a MON, tais como adsorção em resinas e parâmetros de massa. Carbono orgânico total (COT), carbono orgânico dissolvido (COD), absorção na região do ultravioleta (UV254) e absorbância específica de luz ultravioleta (AEUV) são usualmente utilizados como parâmetros de massa. O fracionamento rápido é uma técnica que usa diferentes resinas para separar frações da MON. Nesse contexto, este trabalho teve como objetivo geral caracterizar a matéria orgânica dissolvida (MOD) em processos de tratamento de água para consumo humano usando o método do fracionamento rápido e os parâmetros COD, UV254 e AEUV. Também foram analisados as variáveis turbidez, cor, pH e alcalinidade. Foram avaliados os efeitos dos processos de coagulação, sedimentação, filtração e adsorção em carvão ativado nas frações que formam a MON. Ácidos muito hidrofóbicos (AMH) constituíram a principal fração da MOD na água estudada, havendo redução de 89% entre a água bruta e o efluente do filtro de carvão ativado granular (CAG). A segunda fração predominante foi de ácidos levemente hidrofóbicos (ALH), reduzidos em 83% ao longo do tratamento. Na água bruta, as frações de matérias hidrofílicas carregadas (MHC) e de neutras (MHN) apresentaram concentrações de 0,11 mg L-1 e 0,04 mg L-1, não sendo removidas pelo tratamento.Natural organic matter (NOM) is a complex matrix of organic compounds originated from natural sources that are present in water bodies. NOM is a known precursor of disinfection by-products (DBP) and affects drinking water treatment processes such as coagulation, disinfection, oxidation, activated carbon adsorption, and membrane filtration. For these reasons, the reduction of NOM in water treatment is important. Several methods are used to characterize and quantify NOM, such as resin adsorption and mass parameters. The latter include total organic carbon (TOC), dissolved organic carbon (DOC), ultraviolet absorption at 254 nm (UV254), and specific UV absorption (SUVA). Rapid fractionation is a technique that uses different resins to separate NOM fractions. The objective of this study was to characterize dissolved organic matter (DOM) in drinking water treatment processes using rapid fractionation and the parameters DOC, UV254, and SUVA. Turbidity, color, pH, and alkalinity were also analyzed. The effects of coagulation, sedimentation, filtration, and adsorption processes on the fractions forming the NOM were evaluated. Very hydrophobic acids (VHA) constituted the main fraction of DOM in the studied water, with a reduction of 89% between raw water and granular activated carbon filter (GAC) respect to raw water. The second predominant fraction consisted of slightly hydrophobic acids (SHA), reduced by 83% throughout the treatment processes. In raw water, the hydrophilic charged (MHC) and neutral (MHN) fractions showed concentrations of 0.11 and 0.04 mg L-1, which were not removed during treatment

Removal of dissolved organic carbon in filtered water complemented with treatment by pre-oxidation with ozone and adsorption on activated carbon

Este trabalho teve como objetivo avaliar as remoções de carbono orgânico dissolvido presente em águas filtradas de estação de tratamento de água com tratamento complementar por pré-oxidação com ozônio e adsorção em carvão ativado granular. Para o estudo de adsorção foi utilizado o método de ensaio rápido em coluna de escala reduzida, com carvão ativado produzido de cascas de coco. Realizou-se a comparação entre as curvas de ruptura para os ensaios com e sem aplicação de ozônio. Os resultados mostraram reduções nas concentrações de carbono orgânico dissolvido no início dos ensaios e após a passagem da água com e sem pré-ozonização pelas colunas ensaio rápido em coluna de escala reduzida seguida de incrementos progressivos das concentrações à medida que se aumentou o volume de leitos tratados. Na fase final dos ensaios, os aumentos de volume de leitos tratados não causaram mudanças significativas nas concentrações efluentes de carbono orgânico dissolvido. O mesmo comportamento foi observado com relação à absorção em radiação ultravioleta a 254 nm. O uso de ozônio previamente à adsorção em carvão ativado granular, usando o método ensaio rápido em coluna de escala reduzida, resultou em maiores reduções na absorbância da luz ultravioleta em 254 nm do que nas concentrações de carbono orgânico dissolvido. As absorbâncias específicas à radiação ultravioleta das amostras ozonizadas foram menores do que as que não receberam ozônio.The objective of this study was to evaluate the removal of dissolved organic carbon in filtered water followed by pre-oxidation with ozone and adsorption on granular activated carbon. The rapid small-scale column test was used for the adsorption essays with activated carbon produced from coconut shells. A comparison was made between the breakthrough curves for tests performed with and without pre-oxidation with ozone. The results showed reductions in dissolved organic carbon concentrations after initial passage of water with and without ozone through the rapid small-scale column test column, followed by progressive increases in concentrations along with the number of the bed volumes. In the final phase of the tests, increases in bed volumes did not cause significative changes in effluent dissolved organic carbon concentrations. The same behavior was also observed with respect to ultra-violet absorbance at 254 nm. The use of ozone prior to adsorption on GAC, using the ERCER method, caused greater reductions on UV254 absorbance than in concentrations of dissolved organic carbon. The specific ultraviolet absorbance values of samples that received ozone were lower than those that were not ozonized

Application of bioenergetic principles to the stoichiometry of biological reactions in wastewater treatment processes

O tratamento biológico de águas residuárias é realizado por microrganismos que utilizam determinado substrato para obtenção de energia e crescimento celular através de reações de oxidação-redução e fermentação. Esses mecanismos podem ser expressos por meio de reações estequiométricas desenvolvidas a partir de princípios da termodinâmica. As reações são dependentes dos compostos doadores e aceptores de elétrons. As equações balanceadas resultantes permitem estimar as necessidades de nutrientes, a variação de pH/alcalinidade, a produção de biomassa e gases e o coeficiente de produção celular associados aos sistemas biológicos de tratamento. Esta nota técnica descreveu a metodologia para cálculo estequiométrico de reações bioquímicas usando princípios de bioenergética, apresentando exemplos para diferentes substratos e aceptores de elétrons.Biological wastewater treatment is performed by microorganisms by means of oxidation-reduction and fermentation reactions that release energy for growth and maintenance. These processes can be represented by stoichiometric reactions developed based on thermodynamic principles. Reactions are dependent on the compounds used as electron donor and acceptor. The overall stoichiometric reactions allow estimations of nutrient requirements, alkalinity/pH changes, biomass and gas production, and yield coefficient. This article described a methodology for stoichiometry calculations using bioenergetic principles, presenting examples with different substrates and electron acceptors

Uso de indicadores para avaliação de usinas hidrelétricas em bacias hidrográficas com múltiplos aproveitamentos

Este artigo apresenta uma metodologia que foi utilizada para fazer-se uma avaliação preliminar de usinas hidrelétricas em uma bacia hidrográfica com múltiplos aproveitamentos. A metodologia baseia-se no uso de cinco indicadores que requerem informações relativamente fáceis de se obter. Os indicadores utilizados foram: (a) tendência de estratificação térmica, (b) cargas de poluentes contribuintes aos reservatórios, (c) cargas de poluentes por unidade de volume de reservatório, (d) cargas admissíveis de nutrientes e (e) relação entre potência gerada e potencial de eutrofização. O método foi aplicado a 30 reservatórios de usinas hidrelétricas de pequeno e médio porte planejadas para a bacia hidrográfica dos rios Taquari-Antas, Brasil. O método pode ser utilizado na fase de inventário, precedendo uma avaliação integrada de toda a bacia através da simulação hidrológica.This paper presents a methodology that was used to make a preliminary assessment of multiple hydroelectric power plants planned to be built in a basin. The methodology uses five indicators that require data that are relatively easily to acquire. The indicators are: (a) thermal stratification, (b) pollutant loading to reservoirs, (c) pollutant loading per unit volume of reservoir, (d) nutrient allowable loadings, and (e) rate between power and eutrophication potential. The methodology was applied to 30 reservoirs of small and medium size hydroelectric power plants that are being planned for the Taquari-Antas river basin, Brazil. The methodology can be applied at the inventory phase, preceding the basin integrated assessment through hydrologic simulation