Academic journal article Journal of Environmental Engineering and Science

Black Liquor and Alkaline Shocks in a Multiple Stage Biological Treatment Plant

Academic journal article Journal of Environmental Engineering and Science

Black Liquor and Alkaline Shocks in a Multiple Stage Biological Treatment Plant

Article excerpt

Abstract: To find the impact that alkaline and black liquor spills have on multiple stage biological treatment plants, trials were made in a MultiBio lab-scale treatment plant. It was shown that the concentration of black liquor was diluted between the multiple stages. The initial bacterial stages were inhibited by high concentration of black liquor but recovered when the concentration decreased. Low pH in the feed contaminated with black liquor gave less inhibition than high pH. In a MultiBio treatment plant the active sludge stages, which are sensitive to toxic spills, are placed after the fast growing bacterial stages and are therefore protected. During normal conditions the activated sludge stages receive low concentrations of biodegradable COD. During the trials extra COD in the form of diluted black liquor induced the COD reduction. To evaluate the results, measured concentrations were compared with a computer model.

Key words: industrial wastewater treatment, toxic effluents, black liquor, MultiBio, computer simulation.

Resume : Des essais ont ete realises dans une usine de traitement Multibio a l'echelle du laboratoire afin de trouver l'impact des deversements alcalins et de liqueur noire sur les usines de traitement biologique a plusieurs etapes. Il a ete montre que la concentration en liqueur noire a ete diluee entre les multiples etapes. Les etapes bacteriennes initiales ont ete inhibees par une forte concentration de liqueur noire mais elles ont recupere lorsque la concentration a ete diminuee. Un faible pH dans l'alimentation contaminee par de la liqueur noire a genere moins d'inhibition qu'un pH eleve. Dans une usine de traitement MultiBio, les etapes de boues activees, qui sont sensibles aux deversements toxiques, sont placees apres les etapes de croissance rapide des bacteries et elles sont donc protegees. Sous des conditions normales, les etapes de boues activees recoivent de faibles concentrations de DCO biodegradable. Durant les essais, une DCO supplementaire sous forme de liqueur noire diluee a cause la reduction de DCO. Pour evaluer les resultats, les concentrations mesurees ont ete comparees a un modele informatise.

Mots-cles : traitement des eaux usees industrielles, effluents toxiques, liqueur noire, MultiBio, simulation par ordinateur.

[Traduit par la Redaction]

Introduction

At Gruvon Mill outside of Karlstad, Sweden, Billerud AB, a new multi stage biological treatment plant, MultiBio, started up during spring 2006. Since biological treatment plants are sensitive to toxic spills it is important to know how much a plant can receive before the cleaning efficiency decreases or in the worst case senario of the microculture dying. If the microculture die it can take months before full efficiency is restored. To learn more about the plant, Gruvon Mill, Kemira Ojy, and VA-ingenjorerna AB jointly finance a research project at Karlstad University. This paper presents some of the results of this project.

At Gruvon Mill, bleached Kraft pulp is produced from both soft and hard wood. The pulp is bleached with chlorine dioxide and used for production of "Kraft paper" at the five paper machines. At Gruvon Mill, neutral sulfite semi chemical (NSSC)-pulp is also produced to be used as fluting at the sixth paper machine.

The MultiBio process

The new treatment plant at Gruvon Mill is a MultiBio plant. MultiBio is a treatment concept where multiple bioreactors are combined to accomplish efficient reduction of organic matter, measured as chemical oxygen demand (COD), chlorate reduction and, at the same time, a low sludge production (Ullman and Martensson 2002). Several Swedish pulp mills use the process (Asplind 2002; Lindh and Martensson 2005; Rodden 2005).

In the MultiBio process, the biological treatment has been divided into three main stages with a total of six compartments. The fast growing biomass formatting bacteria are located in the first stage, the bacteria stage, which consists of two compartments. …

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