Influence of the characteristics of paper mill sludges on their anaerobic digestion

The objective of this study was to characterise the anaerobic degradation of three paper mill waste water treatment residues in the shape of sludges and to correlate this anaerobic digestion to the physico-chemical characteristics of the paper sludges. After a deep characterisation of each paper sludge in their initial stage, several parameters were analysed on each paper sludge in mesophilic conditions for 40–50 days: pH, conductivity, chemical oxygen demand, total organic acids and organic fibres degradation. A special care was taken to identify and quantify the volatile fatty acids (VFAs) produced by the digestion using gas chromatography coupled with a mass spectrometer. The results showed that in paper sludges, cellulose mainly degrades over time while the degradation of the other fibres (hemicellulose and lignin) is limited. Consequently, the greater the cellulose content in a paper sludge, the greater the digestion and formation of VFAs. However, not all the cellulose degrades because of a shielding effect of lignin on cellulose, and a pH buffering effect of the calcium carbonate present in the paper sludges limits the hydrolysis-acidogenesis step of the anaerobic digestion. Finally, the gas chromatography–mass spectrometry (GC-MS) investigations showed that acetic acid is the main VFA produced by the anaerobic digestion of paper sludges. This work helps predicting paper mill sludge evolution in the purpose of using them in circular economy.

Partial Replacement of Cement with Waste Paper Sludge Ash

Cement production is one of the sources that emit carbon dioxide, in addition to deforestation and combustion of fossil fuels also leads to ill effects on environment. The global cement industry accounts for 7% of earth’s greenhouse gas emission. To enhance the environmental effects associated with cement manufacturing and to constantly deplore natural resources, we need to develop other binders to make the concrete industry sustainable. This work offers the option to use waste paper sludge ash as a partial replacement of cement for new concrete. In this study cement in partially replaced as 5%, 10%, 15% and 20% by waste paper sludge ash in concrete for M25 mix and tested for compressive strength, tensile strength, water absorption and dry density up to the age of 28days and compared it with conventional concrete, based on the results obtained, it is found that waste paper ash may be used as a cement replacement up to 5% by weight and the particle size is less the 90µm to prevent reduction in workability. Keywords: slump test, Compressive strength, split tensile strength, water absorption test, Waste Paper Sludge Ash Concrete, Workability.

Synthesis of Zeolitic Material with High Cation Exchange Capacity from Paper Sludge Ash Using EDTA

Paper sludge ash (PSA) typically has a low Si abundance and significant Ca content because of the presence of calcite fillers, which interfere with the zeolitic conversion of PSA. Ca-masking with ethylenediaminetetraacetic acid (EDTA) was used to reduce Ca interference during zeolite synthesis so that a zeolitic product with a high cation exchange capacity (CEC) could be synthesized. Hydroxysodalite, zeolite-P, hydroxycancrinite, tobermorite, and zeolite-A can be synthesized from PSA by an alkali reaction with EDTA. With the addition of EDTA, calcium ions in the solution were trapped by chelation, and the number of zeolitic crystals with low Si/Al (Si/Al = 1), zeolite-A, increased owing to the promotion of the synthesis reaction. A product with a high CEC that has a high zeolite-A content was obtained. The chelating agent can inhibit Ca interference for zeolite synthesis by Ca-masking, and a product with a high zeolite-A content can be obtained from PSA using EDTA.