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Studies to Avoid Decreased Efficiency in Multiple Stage Biological Wastewater Treatment Plants: Concerning Forests Industry Effluents
Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [sv]

Målet med den här studien är att förhindra effektivitetssänkningar i moderna biologiska reningsanläggningar för skogsindustriella avloppsvatten. Biologiska processer är vanligtvis effektiva när det gäller att reducera lättnedbrytbart organiskt material. Eftersom den utgörs av levande mikroorganismer (MO) är tekniken känslig. Toxiska ämnen kan döda en kultur av MO. Innan de har ökat i antal igen kommer reduktionseffektiviteten att vara påverkad för en ansenlig tid framöver. I ett pappers- och massabruk finns många typer av vätskor som oavsiktligt kan hamna i reningsanläggningen. I den här studien har svartluts inverkan på reduktionsgraden studerats.

Biologiska reningsverk har använts under en lång tid. De har utvecklats från att vara generella reningsverk till att bli konceptanläggningar i flera steg, där varje steg har designats för sitt eget syfte med specifika MO. I det här arbetet har ett MultiBio-koncept vid Gruvön Bruk studerats. En anläggning i laboratorieskala har byggts för svartlutsförsöken. Resultatet har jämförts mot simulerade värden och värden från bruket.

När ett spill av svartlut passerar genom en MultiBio späds det ut mellan varje steg. Halten av svartlut är hög i de första stegen vilka påverkas kraftigt. I de första stegen lever snabbväxande organismer som återhämtar sig på ett par dagar. De mer känsliga aktivslamstegen finns längre bak i reningsverket och är skyddade från toxiska koncentrationer av svartlut. Endast vid försök med 24-timmarstillsatser blev koncentrationen av svartlut så hög att den påverkade MO negativt.

Den biologiska processen i ett reningsverk kan störas om MO förnekas något essentiellt behov. En biologisk process har ett flertal behov, bland annat behöver aeroba MO löst syre. Eftersom syresättning av vattnet är energikrävande och kostsamt är det inte problemfritt att skapa en omgivning som ger hög effektivitet samtidigt som man strävar efter att sänka energiförbrukningen. I avhandlingen beskrivs ett tillvägagångssätt för att studera energieffektiv syresättning.

Abstract [en]

The aim of this study is to prevent efficiency reduction in modern wastewater treatment plants for forest industry effluents. Biological processes are usually efficient in reducing biodegradable organic material. Since the technique depends on living microorganisms (MO) it is sensitive. Toxic substances can kill the population. It takes considerable time for the MOs to grow in number and the treatment efficiency will be affected accordingly. In a pulp and paper mill, a number of liquors are handled that can reach the treatment plant by accident. In this study the impact of black liquor spills on treatment efficiency has been studied.

Biological treatment methods have been used for a long time. They have developed from general treatment plants to multiple stage concepts, where each stage is designed for its own purpose with specific MO cultures. In this thesis, a plant with the MultiBio concept, located at Gruvön Mill in Sweden has been studied. A laboratory scale MultiBio plant has been constructed for the trials in which efficiency during black liquor exposure has been measured. The measured laboratory results were evaluated by comparing them with simulated values and a mill case.

When a shock of toxic black liquor passing through a MultiBio concept, the black liquor is diluted between the compartments. The first compartments that are exposed to high concentrations of black liquor are affected negatively. The MOs in the first compartment are fast growing and recover in a few days. The more sensitive activated sludge compartments are located further on in the plant. A toxic concentration is found in the activated sludge compartments only when the duration of the spill is 24 hours or more.

Denying the MOs their needs can disturb biological treatments. Among many things, a biological process needs dissolved oxygen. Since aeration is energy consuming and expensive, there is a conflict between gaining high efficiency and, at the same time, decreasing the energy consumption. In this study, an approach to saving energy for aeration is initiated.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2008. , p. 40
Series
Karlstad University Studies, ISSN 1403-8099 ; 2008:1
Keywords [en]
Wastewater treatment, Forest industry, Black liquor, MultiBio, Toxic effluents
National Category
Other Environmental Engineering
Research subject
Environmental and Energy Systems
Identifiers
URN: urn:nbn:se:kau:diva-1416ISBN: 978-91-7063-158-0 (print)OAI: oai:DiVA.org:kau-1416DiVA, id: diva2:5298
Presentation
2008-02-07, 203, 9C, 10:00
Opponent
Supervisors
Available from: 2008-02-11 Created: 2008-02-11 Last updated: 2011-12-21
List of papers
1. Black Liquor and Alkaline Shocks in a Multiple Stage Biological Treatment Plant
Open this publication in new window or tab >>Black Liquor and Alkaline Shocks in a Multiple Stage Biological Treatment Plant
2008 (English)In: Journal of Environmental Engineering and Science, ISSN 1496-2551, E-ISSN 1496-256X, Vol. 7, no 4, p. 335-344Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Energy Systems
Research subject
Energy Technology
Identifiers
urn:nbn:se:kau:diva-1985 (URN)10.1139/S08-007 (DOI)
Available from: 2008-02-11 Created: 2008-02-11 Last updated: 2017-12-07Bibliographically approved
2. Mill Case, Simulation and Laboratory Plant Study of Black Liquor Spill Effects on a Multiple Stage Biological Treatment Plant
Open this publication in new window or tab >>Mill Case, Simulation and Laboratory Plant Study of Black Liquor Spill Effects on a Multiple Stage Biological Treatment Plant
2009 (English)In: Canadian journal of civil engineering (Print), ISSN 0315-1468, E-ISSN 1208-6029, Vol. 36, no 5, p. 839-849Article in journal (Refereed) Published
Abstract [en]

In this study, the impact of black liquor shocks on multiple stage biological treatment plant was studied. The tests were carried out in a lab scale plant and using a mathematical simulation model. The results showed good relation to a parallel situation at the Gruvön Mill. The MultiBio concept is persistent to short-term black liquor spills due to the design where the black liquor is diluted between every compartment. According to the lab scale trials, short-term shocks (5 and 10 h) of black liquor addition reduce bio activity in the first part of the MultiBio plant. Oxygen uptake rate and chemical oxygen demand (COD) degradation decreased during high concentrations of black liquor and increased when the black liquor concentration declined. Protozoas disappeared from compartments exposed to high concentrations of black liquor. A long-term trial encompassing 24 h of black liquor addition inhibited the COD reduction in the whole plant for several weeks.

National Category
Energy Systems
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-1986 (URN)10.1139/S08-056 (DOI)
Available from: 2008-02-11 Created: 2008-02-11 Last updated: 2017-12-07Bibliographically approved

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