Integrated Treatment of Cork Processing Wastewaters for Potencial Reuse

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Organizational Unit

Publications

Redução da toxicidade e aumento da biodegradabilidade dos efluentes do cozimento da cortiça através da integração de tecnologias de membrana e ozonização

Publication . Santos, Diana Cardoso Marques dos; Gomes, Arlindo Caniço

A operação de cozimento da cortiça, destinada à purificação da matéria-prima, requer elevados consumos específicos de água e origina um efluente com cor escura intensa, composição complexa e elevada carga orgânica. Porém, a rentabilidade da produção e transformação da cortiça podem ser beneficiadas se a indústria reduzir o consumo de água e as emissões poluentes. Esta investigação iniciou-se com a recolha e caraterização de uma amostra de efluente, a qual confirmou uma carga poluente elevada, carência química de oxigénio (CQO) de 1 536 mg L-1 e de fenóis totais (FT) de 110 mg ácido tânico L-1, e valores de carência bioquímica de oxigénio após 5 e 20 dias de incubação de 407 mg O2 L-1 e a 554 mg O2 L-1, respetivamente, ou seja com razões CBO5/CQO e CBO20/CQO de 0.26 e 0.36, respetivamente; as quais limitam a possibilidade de concretizar a depuração através de processos biológicos. A utilização sequencial de membranas de ultrafiltração (UF) com coeficiente de exclusão molecular (CEM) de 100, 50, 20 e 10 kDa permitiu obter o fracionamento dos compostos orgânicos em função da sua dimensão molecular, obtendo-se no final das operações em descontínuo 5 frações contendo os poluentes superiores a 100 kDa, entre 50-100 kDa, 20-50 kDa e 10-20 kDa e inferiores a 10 kDa. A caraterização das frações permitiu obter a distribuição mássica da CQO, FT e cor, a qual determinou que os compostos com dimensão superior a 50 kDa são responsáveis por 72% da CQO, 81% dos FT e 83% da cor do efluente. Concluiu-se que a biodegradabilidade, toxicidade (Microtox), e os valores de CQO, FT e cor podem ser correlacionados com a dimensão e com os CEM das membranas. Os resultados da oxidação química das frações com ozono, limitado a razões Ozonoaplicado/CQOinicial entre 0.15 e 0.60, permitiram remoções da CQO, FT e cor entre 16.6 e 69.4%, 67.7 e 95.7% e entre 10 e 96.5%, respetivamente; e o aumento a biodegradabilidade, a qual é primariamente limitada pela dimensão. O recurso à cromatografia de alta resolução (HPLC) com detetores de diodo array (DAD) e de espetrometria de massa permitiu quantificar 7 poluentes específicos e confirmar que a natureza e composição complexa do efluente e das frações permitem a ocorrência de reações de clivagem, degradação e associação, algumas favorecidas pelo ozono, que resultaram em razões de recuperação (todas as frações incluídas) expressas em percentagem, entre 0 e 415%. Os resultados obtidos permitem suportar a viabilidade técnica e económica da integração da UF, oxidação química e tratamento biológico nos sistemas de depuração do efluente do cozimento da cortiça, contribuindo assim para a redução do consumo de água através da possibilidade de reutilização dos permeados.

2013-05Master thesis

Open access

Toxicity reduction and biodegradability enhancement of cork processing wastewaters by ozonation

Publication . Gomes, A.C.; Silva, Lúcia; Simões, Rogério; Canto, N.; Albuquerque, Antonio

Biodegradability enhancement and detoxification of cork boiling wastewater (CBW) are required for the successful implementation of biological treatment options. We studied the possibility of achieving these goals through ozonation pre-treatment by experimenting on the effect of ozone dose and pH. The CBW used had a pH of 5.81, a chemical oxygen demand (COD) of 1,865 mg L-1, a biochemical oxygen demand (BOD5) of 498 mg L-1 and total phenol (TP) and tannin compounds concentrations of 523 and 399 mg L-1, respectively. The ozone doses ranged from 0.27 to 2.63 for the O-3(applied)/COD0 ratios with samples at natural pH and set to 3.33 and 9.96. Ozonation allowed the BOD20/COD ratio (biodegradability index) to increase from 0.37 to 0.63 and a toxicity reduction from 3.08 to 1.24 TU (Microtox). The corresponding removals obtained were 15.2-62.0%, 38.4-83.2% and 56.7-92.1% for COD, TP and colour, respectively. The best outcome of ozonation pre-treatment requires O-3(applied)/COD0 ratios over 1.5 and an acid pH. The increase of TP removals with ozone dose at acid pH led to biodegradability enhancement and CBW detoxification. However, for similar conditions the highest COD removals were obtained at alkaline pH due to the hydroxyl radicals' high oxidation ability but lack of selectivity.

2013-10Journal article

Open access

Investigation of lab-scale horizontal subsurface flow constructed wetlands treating industrial cork boiling wastewater

Publication . Gomes, Arlindo; Silva, Lúcia; Albuquerque, Antonio; Simões, Rogério; Stefanakis, Alexandros

The feasibility and treatment efficiency of horizontal subsurface flow constructed wetlands (HSFCW) was assessed for the first time for cork boiling wastewater (CBW) through laboratory experiments. CBW is known for its high content of phenolic compounds, complex composition of biorecalcitrant and toxic nature. Two lab-scale units, one planted with Phragmites australis (CWP) and one unplanted (CWC), were used to evaluate the removals of COD, BOD, total phenolic compounds (TPh) and decolourization over a 2.5-years monitoring period under Mediterranean climatic conditions. Seven organic and hydraulic loading rates ranging from 2.6 to 11.5 g COD/m2/d and 5.7e9.1 L/m2/d were tested under average hydraulic retention time (HRT) of 5 ± 1 days required due to the CWB limited biodegradability (i.e., BOD5/ COD of 0.19). Average removals of the CWP exceeded those of the CWC and reached 74.6%, 91.7% and 69.1% for COD, BOD5 and TPh, respectively, with respective mass removals rates up to 7.0, 1.7 and 0.5 (in g/m2/d). Decolourization was limited to 35%, since it mainly depends on physical processes rather than biodegradation. CBW concentration of nine phenolic compounds ranged from 1.2 to 38.4 mg/L (for the syringic and ellagic acids, respectively) in the raw CBW, with respective removals in the CWP unit ranging from 41.8 to 76.3%, higher than those in the control unit. Despite CBWhigh concentration of TPhs (average of 116.3 mg/L), the HSFCW reached organic load removals higher than those of conventional biological treatment methods.

2018Journal article

Embargoed access

Biodegradability enhancement and detoxification of cork processing wastewater molecular size fractions by ozone

Publication . Santos, Diana C.; Silva, Lúcia; Albuquerque, Antonio; Simões, Rogério; Gomes, A.C.

Cork boiling wastewater pollutants were fractionated by sequential use of four ultrafiltration membranes and five fractions were obtained: four retentates (>100, 50-100, 20-50 and 10-20 kDa) and one permeate (<10 kDa); which were used to study the correlation of molecular size with biodegradability and toxicity before and after ozonation. The results show that molecular size is correlated with organic load and restrains biodegradability. The fraction with >100 kDa corresponds to 56% of the organic load and the one with <10 kDa only 8%. The biodegradability of fractions increased 182% with fractions molecular size reduction from >100 to < 10 kDa and the chemical oxygen demand (COD) was from 3436 to 386 mg L-1. For biodegradability enhancement the best outcome of ozonation was obtained with compounds having molecular size >20 kDa and range from 5% up to 175% for applied ozone doses to COD ratios between 0.15 and 0.38.

2013-11Journal article

Open access

Cork Boiling Wastewater Treatment in Pilot Constructed Wetlands

Publication . Gomes, A.C.; Stefanakis, Alexandros; Albuquerque, António; Simões, Rogério

most studies published on the topic of cork boiling wastewater (CBW) treatment or valorization used physico-chemical treatment options rather than biological processes. However, the related costs are high and above those of the biological treatment alternative for wastewaters with similar organic loads but from different sources. Thus, con- structed wetland systems (CWs) can be an alternative to conventional biological treatment systems, namely to activated sludge systems, with the prominent virtues of low construction and operation costs. Until today, there is no study or research published for the treatment of CBW using CW systems. Thus, this investigation is a novelty and included the monitoring over a period of four years of the operation of a horizontal subsurface flow constructed wetland (HSF CW) microcosm-scale system planted with common reeds (Phragmites australis) and filled with light expanded clay aggregates (LECA), as support media for the plants and for biofilm development. The contribution of plants to the treatment was assessed by the comparison with an identical wetland unit without plantation (control bed). After this extended period of operation intended to maximize biomass development and acclimatization, which included stepwise increase of the organic load rate (OLR) up to 8.9 g COD/m2/d, the assessment of the treatment capacity of the system was done by doubling the OLR to 16.4 g COD/m2/d during 200 days.

2018Book part

Open access