Chemical and leaching properties of paper mill sludge

Abstract

Paper mills produce large amounts of paper mill sludge in the treatment of process water. According to overburden studies, the hydraulic conductivity of the paper mill sludge originating from a paper mill in Northern Finland at a pressure of 30 kPa was 4.4610 À 10 m s À 1 , and 1.7610 À 10 m s À 1 at a pressure of 100 kPa. These values well meet the generally required values of between 1.0610 À 7 m s À 1 and 1.0610 À 9 m s À 1 for a geological barrier in landfill base and sides at landfills in the European Union. Paper mill sludge can also be used in the artificially constructed geological barrier layer of landfill cover structures. The angle of internal friction of the paper mill sludge was 34.8 and the cohesion of interparticle adhesion 23 kPa, which are important measures for assessing the shear strength of paper mill sludge and thus the stability of the landfill layer in which it is used. During a 28-day period, the biodegradability of the paper mill sludge in soil was ca 0.4% and in ground water under 1%, whereas according to the OECD 301F standard concentrations (BOD 28 ), it was ca 8%. For the determination of total element concentrations in the paper mill sludge, the dried sample was digested using USEPA method 3052. A five-stage sequential leaching procedure was also used to fractionate trace elements in the paper mill sludge between the water-soluble (H 2 O), exchangeable (CH 3 COOH), easily reduced (HONH 3 Cl), oxidizable (H 2 O 2 þ CH 3 COONH 4 ), and (5) the residual (HF þ HNO 3 þ HCl) fractions. This paper covers also examples of case studies how paper mill sludge is utilized in Finland.

Hydrothermal carbonization of lignocellulosic biomass: Effect of process conditions on hydrochar properties

“…The resulting hydrochar contained significant quantities of non-soluble ash (Fig. 2a), most likely in the form of calcium carbonate, kaolinite and quartz which are typically found from sludge residues within the pulp and paper industry [37,38]. Assuming CaO was present as calcium carbonate (CaCO 3 ), Al 2 O 3 as kaolinite (Al 2 Si 2 O 5 (OH) 4 ) and the remaining SiO 2 as quartz (SiO 2 ), the respective mineral phases constituted 46%, 15% and 8% of the original feed ash.…”

Pretreatment of recycled paper sludge with a novel high-velocity pilot cyclone: Effect of process parameters on convective drying efficiency

“…Within the pulp and paper industry, the quantities and chemical composition of sludge streams depend on the paper grade being produced, specific fresh water consumption, applied wastewater treatment technique and the types of raw materials used in production [1,5]. Wastewater treatment processes generally consist of mechanical primary treatment by, e.g., gravity settling followed by secondary treatment using chemical or biological methods [1,4,6].…”

Pulp and Paper Mill Fly Ash: A Review

“…The environmental protection agency recommends regularly testing the environmental compatibility of fly ash when it is used as a geomaterial in real-life applications such as construction and geotechnical projects. In the past, several studies have been carried out to evaluate the leachate characteristics of a wide variety of fly ashes from different sources [15,23,39,[55][56][57][58][59][60]].…”