Combined biological and advance oxidation processes for paper and pulp effluent treatment

A thesis submitted in fulfilment of the requirements f Master of Science in Engineering to the School of Chemical and Metallurgical Engineering, Faculty of Engineering, University of the Witwatersrand, Johannesburg, 2017Recently, the South African paper and pulp industry has become increasingly interested in the development of suitable wastewater treatment technologies able to assist in the closure of the water network and also to minimize their environmental footprint at their sites. Factors such as the rising cost of fresh water, stricter environmental legislation and socio-political pressure have forced water intensive users to become less dependent on the municipalities. The research described here addresses wastewater problems from two separate mills. Mill X (Case A) is relying on the municipality for fresh water and the treatment of their effluent. The mill wants to become less dependent on the municipality by closing the water network (zero effluent discharge). A wastewater treatment plant (WWTP) would be required to reduce the chemical oxygen demand (COD), total suspended solids (TSS) and colour before any processes water could be reused. Mill Y (Case B) is currently using their effluent for the irrigation of the local plantation. The mill would like a wastewater treatment plant able to reduce the biodegradable material prior to irrigation. Excessive amounts of biodegradable organics in the effluents can cause bacterial and fungal growth in the irrigations systems and consequently clogging problems. More advanced treatment steps would also be required to lower the bio-recalcitrant COD to environmental discharge limits (<400 mg/L). As a result, this study investigated the potential of combining biological and advanced oxidation processes (AOP) for effluent treatment at both mill effluents. An extensive literature study on the treatment of paper and pulp mill effluents was conducted to get a comprehensive understanding of the treatment technologies/combinations. The treatment of paper and pulp mill effluents can be divided into three distinct treatment stages namely: Primary treatment: For the removal of the total suspended solids (TSS) Secondary treatment: For the removal of the biochemical oxygen demand (BOD) Tertiary treatment: Mainly for the removal of bio-recalcitrant chemical oxygen demand (COD) and colour Mill X and Mill Y already contained primary clarifiers to remove the majority of the total suspended solids (TSS). Consequently, the secondary and tertiary treatment steps were evaluated. A detailed technology selection assessment was done to select the best suited secondary and tertiary treatment technologies for the purpose of this project. The work demonstrated that an aerobic MBBR could be used in combination with Fenton related treatment technologies in order to comply with the individual mill specifications. The applicability of both these biological and AOP treatment solutions was therefore extensively investigated. The results indicated that the aerobic moving bed biofilm reactor (MBBR) was able to remove the majority of the biodegradable organics from the recycle and neutral semisulfite chemical pulping mill effluents. The optimal COD removal efficiency ranged between 46% and 57% for the various effluents. The effluent from Mill X was generally found to be more readily biodegraded than the effluents from Mill Y. Experimental results indicated that certain effluents contain organics that display antimicrobial properties. The maximum substrate removal rate decreased linearly with an increase in phenols. As a result, it was therefore assumed that lignin derived alkyl phenols might have inhibited aerobic and anaerobic microbial digestion processes. The results indicate that the MBBR system was not fully acclimatized for high phenolic wastewaters. It is therefore recommended that future experimental studies consider the effects of phenolic content and employ longer acclimatization periods. A significant fraction of the paper and pulp mill effluents were considered to be bio-recalcitrant and required tertiary treatment to be removed. It was found that both the Fenton (Fe3+/H2O2) and Fenton-like (Fe3+/H2O2) oxidation processes can remove bio-recalcitrant organics from biologically treated mill effluents (BTME). However, preliminary experimental results indicated that the Fenton process had a faster oxidation rates. For the Fenton process, the optimal COD removal efficiencies ranged between 40% and 67% for the BTMEs. The experimental results also demonstrated that a combination of Fenton oxidation and slaked lime treatment can effectively remove the colour of BTMEs (97%). The COD removal rates for the neutral sulfite semi-chemical (NSSC) effluents were found to be higher than that of the recycle mill effluent (RME). The aromatic and volatile organic acid (VOA) content of the BTMEs had an important role in the oxidizing processes. The BTMEs with a higher volatile organic acid (VOA) content generally had slower oxidizing rates. The experimental results indicated that the combination of an aerobic MBBR and Fenton process can be implemented at both paper and pulp mills to assist with their individual treatment requirements. An economic study for Case A (Mill X) was also conducted. The data obtained throughout this study was linked to previous water optimization work done at the mill. The economic analysis demonstrated that the aerobic moving bed biofilm reactor (MBBR) and Fenton treatment combination could treat the recycle mill effluent for reuse in a cost-effective manner. The total capital investment cost of the treatment plant was estimated to be R28.5 million and the operational cost was found to be R12.21/m3 of wastewater. The implementation of this treatment solution on the water network could save the mill approximately R 1.25 million/year. The rising cost of fresh water and discharge might increase the economic feasibility of such a WWTP in the near future.XL201

Fibres and energy from wheat straw by simple practice

The overall purpose of this work is to evaluate the possibilities of wheat straw for fibre and energy production and address the question of whether or not it is possible to develop a cost-effective process for producing good quality pulp from wheat straw for current paper or paperboard products. In addition, in light of the green energy boom, the question of whether fibre production could give added value to energy production using wheat straw is addressed. Due to the logistics of the bulky raw material, the process should be applied on a small scale that determines the requirements for the process. The process should be simple, have low chemical consumption and be environmentally safe. The processes selected for the study were based on an initial hot water treatment. Actual defibration in the "chemical" approach was then performed using a subsequent alkaline peroxide bleaching process or in the "mechanical" approach through mechanical refining. In both approaches, energy can be produced from lower quality material such as dissolved solids or fines. In this work, one of the primary aims besides the development of the abovementioned process is to investigate the chemical storage of wheat straw which decays easily between harvesting periods and examine its effects on pulping and pulp properties. In addition, the aim of this work is to determine the market potential for non-wood pulp and evaluate non-wood pulp production. The results showed that the "chemical" approach produced fibres for printing and writing. The quality of the pulp was relatively good, but the chemical consumption at the target brightness of 75% was high, indicating that a chemical recovery would be needed unless the brightness target could be significantly reduced. The "mechanical" approach produced unbleached fibres for fluting and the energy production from fines and dissolved solids generated additional income. The results also showed that it is possible to store wheat straw chemically with formic acid-based chemicals over a year without significant changes in the chemical composition. The chemical storage can be integrated with the suggested chemical or mechanical defibration process, soda pulping process or any other process utilising non-wood fibres. In China, a clear demand for non-wood-based fibres exists due to a shortage of fibre and also because of the increasing demand for bioenergy. In Europe, the competitiveness of non-wood fibre utilisation will only be established if combined with energy production

Innovations of the forest industry in the 21st century

Forests are the most important natural resource in the Finnish society. The forest industry provides access to valuable natural resources that is part of people’s daily life. In addition, the forest industry is a significant contributor to the Finnish economy by promoting employment and well-being of society. The 21st century has been a critical period for the forest industry. While demand for traditional forest products has started to decline, the forest industry has been criticized for being a polluting sector with lack of innovativeness. In this respect, continuous development has been conducted in the industry, which has further enabled the renewal of the industry and update of image to this day. By examining innovations behind the development, the performance of the industry in the midst of major changes can be evaluated. This thesis studied the innovations enabling the development and renewal of the forest industry in the 21st century. The aim of the study was to compile the most significant process technology and product innovations from different fields and themes, as well as to study the factors driving the emergence of innovations. For this, a quality study was conducted through semi-structured interviews with experts in the field. In addition to innovations, achievements and their key performance indicators were studied, and further, experts’ perception of prospects for the industry were inquired. The results revealed that resource efficiency has been the most significant driver for equipment, technology and component developments during the 21st century. Another major driver was sustainability and related environmental issues, which have been a source of inspiration for new material and product innovations and above all, for the development of start-ups. Many innovations and innovative solutions have been able to identify in this work. It should be taken into consideration that the availability of results might have been affected by changing operating environment and intensified competition. Nevertheless, the future of the forest industry is considered as positive. Bioeconomy and sustainability challenges like climate change appeared to be the key factors driving the innovation in the forest industry

Properties affecting the rheology of alkaline cellulose solutions

Cellulose is the most abundant biopolymer on earth and it is a versatile building block for multiple purposes, for example in paper, board and textile industries, and as its derivative form, such as cellulose acetate, ethers or esters, it can be exploited for example in pharmaceuticals and packaging. However, utilization of cellulose in high performance purposes requires its dissolution, in order to enable the regeneration of the structure. Cellulose dissolution is challenging due to the semi-crystalline structure, tight hydrogen bonds within the polymer sheets and the structure with both hydrophilic and hydrophobic heads. For this reason, cellulose structure first needs to be altered through derivatization or otherwise increasing its accessibility, for example by means of enzyme treatment prior to dissolution. The aim of the study was to compare different activation mechanisms and raw materials, and examine how these factors affect the solution rheology and stability. The latter is a significant factor affecting processability of the solution in regeneration of the solution into a form of fibres or films. Literature part covers chapters of cellulose structure, different activation mechanisms and dissolution, as well as factors affecting it. Additionally, theory shortly discusses of the features affecting regeneration and rheology of solution. Experimental part consists of dissolving cellulose pulps with different pretreatments, after which, solutions are examined in means of solubility and stability. As a reference material, viscose performed as expected, exhibiting the highest level of dissolution, and gelled after around five days. Most importantly, enzyme-treated cellulose exhibited positive effect on solution stability, remaining processable longer that viscose. It was also concluded that consisted process conditions cannot be applied for different raw materials without optimizing the process for each raw material individually

Life Cycle Assessment (LCA) technique as a holistic tool for environmental impact and economic analysis of a co-pulping process

As the pressure on the chemical and process industries to improve environmental and economic performance increases, the need to move away from narrow system definitions and concepts in environmental system management is becoming more apparent. Life Cycle Assessment (LCA) has been a gaining wider acceptance as a holistic tool that enables quantification of environmental interventions and evaluation of the improvement options throughout the life cycle of process, product or activity. The stringent environmental legislation, especially in developing countries has warranted the need for intensive research in this field. Moreover, the capital cost for mitigation of emissions have put enormous pressure on the industries to reduce the overall process economic performance. This has not exempted the Pulp and Paper industry, being the producers of highly variable emissions quality and quantity are the prime candidates for the application of the technique. The application of the LCA in process selection has been necessitated by the fact that sometimes a technology intended to reduce wastes has created unanticipated impacts in other media and/or stages of the life cycle. Thus, LCA has been developed as a means to identify and deal with these impacts before they can occur. It differs from other pollution prevention techniques in that it views all the resource and energy inputs to a product (Life Cycle Inventory), as well as the associated wastes, health and ecological burdens (Impact Assessment), and evaluates opportunities to reduce environmental impacts (Improvement Analysis) from cradle to grave. LCA is often confused with other assessment tools, such as life cycle cost (LCC) or sometimes referred to as "environmental life cycle costing." This study was conducted at Mondi Packaging South African-Piet Retief Mill, a producer of linerboard, since this site has ample opportunity to minimse the environmental burden presented by operation of both Copeland Reactor and Boilers with significant emissions of SOx and NOx, and water effluent. The current mill strategy that is based on tight procurement specification of raw material is unsustainable. The environmental and economic performance analysis for this study followed from a mass balance of the pulp plant, power station, and paper machine as well as black liquor incinerating plant, and it was found that the most significant emissions come from pulp and steam generating processes. These emissions can be reduced by improving the mill energy efficiency and optimizing the Copeland scrubber absorption efficiency. The optimization of the Copeland scrubbing system will surely lead to improved environmental performance, however, the furnace stacks have to be modified to include the scrubbing system for absorption of SOx and NOx.Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2008.Chemical Engineeringunrestricte

End-of-waste criteria for waste paper: Technical proposals

This report presents proposals of end-of-waste (EoW) criteria for waste paper, defining the technical requirements that waste paper has to fulfil in order to cease to be waste in the EU. The report includes the background data and assessments used to support the proposals, including a comprehensive techno-economic analysis of waste paper recycling, and analyses of the potential economic, environmental and legal impacts when waste paper ceases to be waste. This report is a contribution to the implementation of the concept of End-of-waste in EU legislation, a mechanism introduced through Article 6 of the Waste Framework Directive (2008/98/EC). The Directive introduces the possibility that certain waste streams having undergone a recovery operation and fulfilling certain criteria – so-called End-of-waste criteria – can cease to be waste. The criteria have to ensure that the waste streams fulfil a number of conditions, including the existence of a commonly used specific applications, existence of a market or a demand, fulfilment of technical requirements for the specific applications, meeting existing legislation and standards applicable to the products the waste streams substitute; and the absence of any overall adverse environmental or human health impacts.JRC.DDG.J.6-Sustainable production and consumptio