Long-term changes in the effluent loads from pulp and paper mills, the introduction of BAT technology, and their effects on extractable organic halogens concentrations in sediment in part of the Bothnian Bay.

The Bothnian Bay at Kemi, which is the northernmost basin of the Gulf of Bothnia in the Baltic Sea, is affected by effluents from point sources such as pulp and paper mills and municipal sewage plant. During the period 1988-2008, the accumulated values of effluent volume, BOD7, CODCr, Tot-P, Tot-N, TSS and AOX from these point sources fell considerably as follows: 1) effluent volume by 24%, BOD7 by 92%, CODCr by 74%, Tot-P by 79%, Tot-N by 38%, TSS by 76% and AOX by 93%. The decrease in the effluent loadings is due to the introduction of Best Available Techniques (BAT) for the production processes and wastewater treatment at the pulp and paper mills. According to the long-term monitoring program that has been carried out every third year between 1997-2009, the decreasing trend in EOX-concentrations in the top 2 cm of the bottom sediment reflects the decrease in organochlorine discharges (AOX) from the mills. In 1997, the EOX concentrations in bottom sediment varied between 3-70 µg of Cl g(-1) (dry weight), and in 2009 between 1.2-31 µg of Cl g(-1) (dry weight).

Chemical and physical properties of cyclone fly ash from the grate-fired boiler incinerating forest residues at a small municipal district heating plant (6MW).

In Finland, the new limit values for maximal allowable heavy metal concentrations for materials used as an earth construction agent came into force in July 2006. These limit values are applied if ash is utilized, e.g. in roads, cycling paths, pavements, car parks, sport fields, etc. In this study we have determined the most important chemical and physical properties of the cyclone fly ash originating from the grate-fired boiler incinerating forest residues (i.e. wood chips, sawdust and bark) at a small municipal district heating plant (6 MW), Northern Finland. This study clearly shows that elements are enriched in cyclone fly ash, since the total element concentrations in the cyclone fly ash were within 0.2-10 times higher than those in the bottom ash. The total concentrations of Cd (25 mg kg(-1); d.w.), Zn (3630 mg kg(-1); d.w.), Ba (4260 mg kg(-1); d.w.) and Hg (1.7 mg kg(-1); d.w.) exceeded the limit values, and therefore the cyclone fly ash cannot be used as an earth construction agent. According to the leached amounts of Cr (38 mg kg(-1); d.w.), Zn (51 mg kg(-1); d.w.) and sulphate (50,000 mg kg(-1); d.w.), the cyclone fly ash is classified as a hazardous waste, and it has to be deposited in a hazardous waste landfill.

EOX concentrations in sediment in the part of the Bothnian Bay affected by effluents from the pulp and paper mills at Kemi, Northern Finland.

The Bothnian Bay, which is the northernmost part of the Gulf of Bothnia in Northern Finland, is affected by effluents discharged from point sources such as the pulp and paper mills of Stora Enso Oyj Veitsiluoto Mill and Oy Metsä-Botnia Ab Kemi Mill at Kemi, and the Kemi municipal sewage plant, as well as the River Kemijoki. In this paper we discuss, how modernisation of the wastewater treatment plant at the mills, and process investments in the Best Available Techniques (BAT) for effluent treatment, have decreased the effluent discharges of biological oxygen demand (BOD), chemical oxygen demand (COD), total phosphorus (Tot-P), total nitrogen (TOT-N), total suspended solids (TSS) and adsorbable organically bound halogens (AOX) from the mills since 1988. One specific aim of the study was to determine the EOX (Extractable Organically Bound Halogens) concentrations in bottom sediment of the Bothnian Bay in order to assess whether the EOX concentrations reflect the reduction in discharges of chlorinated compounds. According to the monitoring program carried out every third year between 1997-2006, the decreasing trend in EOX concentrations in the top 2 cm of the bottom sediment reflect the decrease in organochlorine discharges (AOX) from the mills. In 1997 the EOX concentrations in bottom sediment varied between 3-70 microg of Cl g(-1) (dry weight), and in 2006 between 3.3-32 microg of Cl g(-1) (dry weight).

Environmental risk assessment of heavy metal extractability in a biosludge from the biological wastewater treatment plant of a pulp and paper mill.

A five-stage sequential extraction procedure was used to fractionate heavy metals (Cd, Cu, Pb, Cr, Zn, Fe, Mn, Ni, Co, As, V and Ba) in a biosludge from the biological wastewater treatment plant of Stora Enso Oyj Veitsiluoto Mills at Kemi, Northern Finland, into the following fractions: (1) water-soluble fraction, (2) exchangeable fraction, (3) easily reduced fraction, (4) oxidizable fraction, and (5) residual fraction. The biosludge investigated in this study is a combination of sludge from the primary and secondary clarifiers at the biological wastewater treatment plant. Extraction stages (2)-(4) follow the protocol proposed by the Measurements and Testing Program (formerly BCR Programme) of the European Commission, which is based on acetic acid extraction (stage 2), hydroxylamine hydrochloride extraction (stage 3), and hydrogen peroxide digestion following the ammonium acetate extraction (stage 4). The residual fraction (stage 5) was based on digestion of the residue from stage 4 in a mixture of HF + HNO3 + HCl. Although metals were extractable in all fractions, the highest concentrations of most of the metals occurred in the residual fraction. From the environmental point of view, it was notable that the total heavy metal concentrations in the biosludge did not exceed the maximal allowable heavy metal concentrations for sewage sludge used in agriculture, set on the basis of environmental protection of soil by European Union Directive 86/278/EEC, and by the Finnish legislation. The Ca (98.6 g kg(-1); dry weight) and Mg (2.2 g kg(-1); dry weight) concentrations in the biosludge were 62 and 11 times higher than the typical values of 1.6 and of 0.2 g kg(-1) (dry weight), respectively, in arable land in Central Finland. The biosludge had a slightly alkaline pH ( approximately 8.30), a high loss-on-ignition value ( approximately 78%) and a liming effect of 10.3% expressed as Ca equivalents (dry weight). This indicates its potential as a soil conditioner and improvement agent, as well as a pH buffer.