Anaerobic treatment of cellulose bleach plant wastewater: chlorinated organics and genotoxicity removal

Abstract

-This study assessed the removal efficiency of organic matter and how it relates to the decrease of toxic and mutagenic effects when an anaerobic reactor is used to treat the bleaching effluent from two kraft pulp mills. Parameters such as COD (chemical oxygen demand), DOC (dissolved organic carbon), AOX (adsorbable organic halogen), ASL (acid soluble lignin), color, chlorides, total phenols and absorbance values in the UV-VIS spectral region were measured. The acute and chronic toxicity and genetic toxicity assessments were performed with Daphnia similis, Ceriodaphnia sp. and Allium cepa L, respectively. The removal efficiency of organic matter measured as COD, ranged from 45% to 55%, while AOX removal ranged from 40% to 45%. The acute toxic and chronic effects, as well as the cytotoxic, genotoxic and mutagenic effects, decrease as the biodegradable fraction of the organics is removed. These results, together with the organic load measurement of the effluents of the anaerobic treatment, indicate that these effluents are recalcitrant but not toxic. As expected, color increased when the anaerobic treatment was applied. However, the colored compounds are of microbial origin and do not cause an increase in genotoxic effects. To discharge the wastewater, it is necessary to apply a physico-chemical or aerobic biological post-treatment to the effluents of the anaerobic reactor.

Anaerobic digestion of alkaline bleaching wastewater from a kraft pulp and paper mill using UASB technique

“…[19,20] Despite the varying results, the above studies indicate that the presence of AOX lowers the COD reduction and methane production. The relatively high AOX-removal efficiencies given for wastewaters with an AOX content of 2.5-42 mg L −1 [19,20,33] made us to expect a high removal in our reactors (AOX levels of 3.5-6.6 mg L −1 ). One reason for our low AOX removal might be the low HRT of 7-14 h compared with 25 h, [20] 40 h [19] and 20 days.…”

“…Buzzini et al [19] treated a synthetic wastewater, simulating the composite effluent from a mill producing bleached and unbleached eucalyptus pulp, in two UASBs with chemical oxygen demand (COD) removals of 76 ± 5% vs. 81 ± 2%. Eucalyptus was also the raw material used in a study by Chaparro and Pires [20] evaluating the biodegradability for a mixture of alkaline and acid bleaching wastewaters in a horizontally packed-bed anaerobic reactor. The AD in this case resulted in a COD removal of 52-55%.…”

Anaerobic Digestion of Wastewaters from Pulp and Paper Mills : A Substantial Source for Biomethane Production in Sweden

“…High-rate AD processes for kraft ECF bleaching wastewaters, have shown a potential to degrade 46-76% of the incoming COD (UASB, Buzzini et al, 2005; anaerobic filter, Vidal et al, 2007; horizontal anaerobic immobilized bioreactor, Chaparro and Pires, 2011; packed bed AD column, Lin et al, 2013). Buzzini et al (2005) evaluated a synthetic wastewater of diluted black liquor with the addition of chlorinated compounds, whereas the others investigated the total bleaching wastewater, including both wastewater from the acidic steps with ClO2 and the alkaline extraction steps.…”

“…Buzzini et al (2005) evaluated a synthetic wastewater of diluted black liquor with the addition of chlorinated compounds, whereas the others investigated the total bleaching wastewater, including both wastewater from the acidic steps with ClO2 and the alkaline extraction steps. Much of the reported research is performed in South America, why eucalyptus (Chaparro and Pires, 2011;Buzzini et al, 2005) or pine (Vidal et al, 2007) are the raw materials mainly used for the pulp production. However, Lin et al (2013) sampled wastewater from the production of a mixed HW pulp (>60% oak, sweet gum and hickory).…”

“…and so far the scientific literature presents varying results for high-rate AD of these kinds of wastewaters (e.g. 46-76% COD reduction; Vidal et al, 2007;Buzzini et al, 2005;Chaparro and Pires, 2011;Lin et al, 2013). Therefore, this type of wastewater needs further attention to facilitate a stable and continuous process.…”