Sediment accumulation of organic halogens in pristine forest lakes: Tracking of a single defined discharge of pulp bleaching wastewater.

Sediment accumulation of organic halogen was studied in two forest lakes, one pristine and one which received 30 m(3) of biologically purified bleaching wastewater from a kraft pulp mill in 1979 equivalent to ca. 2 kg of adsorbable organic halogen (AOX). Lake sediments were dated with(210)Pb,(134)Cs and(137)Cs and the annual deposition rates of organic halogens and organic matter were calculated. Organic bound halogen contents of the sediment aged 150 years was 180 microg Cl g(-1) d.w. in both lakes. The concentration of organic bound halogen at the topmost 6 cm of the sediments (less than 20-years-old) ranged from 45 to 80 microg Cl g(-1) d.w. This suggests that solvent extractable halogen had enriched in the older sediment layers. The deposition of extractable organic halogen (EOX) in the lakes in 1950's was 4 to 5 mg Cl m(-2) a(-1). Since then, the deposition of EOX doubled in both lakes. The deposition of organic matter increased concomitantly from 50 g m(-2) a(-1) to 110 g m(-2) a(-1) in Lake Mustalampi and from 35 g m(-2) a(-1) to 62 g m(-2) a(-1) in Lake Pyylampi suggesting that the increase in the deposition of organic halogen followed the increase in the deposition of organic matter. Of the 2 kg of organic halogen discharged into the lake, 5% or less was detected in the sediment in tetrahydrofuran extractable form 15 years later.

Anaerobic fluidised bed for the purification of effluents from chemical and mechanical pulping.

Anaerobic treatment has seldom been used for wastewaters from the pulp and paper industry and other branches of the chemical industry. Escape of volatile pollutants to the atmosphere, which always occurs during aerobic treatment, is avoided, and much less sludge is being produced than in an aerobic process. The greatest obstacle for using anaerobic treatment in the pulp and paper industry is the large wastewater volume, which necessitates short hydraulic detention times, because the treatment is to occur in an enclosed space. We used solid carrier particles to prevent wash-out of biomass from the reactor at high hydraulic loading, and an up-flow system in order to be able to use very small carrier particles, maximizing the surface area for biomass attachment. In this paper we describe and discuss the results obtained with this type of anaerobic reactor (fluidised bed) at bench and semitechnical scale for wastewaters from pressurized ground wood pulping and paper manufacture, sulphite pulp evaporator condensate and bleach waste. Earlier work with Kraft pulp bleaching effluent and thermomechanical pulping wastewater and evaporator condensates using anaerobic reactors is also discussed. The results obtained thus far show that there are several wastewater streams from the pulping industry, where 60 to 90% of the dissolved organic pollutants (measured as COD(Cr) or TOC) was biodegraded within 4 to 24 h. The high strength waste streams (COD(Cr) >2000 mg O(2) 1(-1)) allowed organic space load of 4 to 10 kg COD(Cr) m(-3) reactor volume d(-1). With low strength wastes the hydraulic loading was the limiting factor.