Treatment Of Pulp Mill Wastewater Research Articles

An integrated approach to explore UASB reactors for energy recycling in pulp and paper industry: a case study in Brazil

Brazil is currently focused on its energy matrix transition in favor of increasing of the share of renewable energy carriers for both enhanced energy security and mitigation of greenhouse gas emissions. In this context, the country`s pulp and paper industry whose different wastes teams are not generally exploited, could play a critical role. Accordingly, the main objective of this work is to develop a conceptual ‘systemic’ biorefinery framework integrating the treatment of pulp and paper mill wastewater using upflow anaerobic sludge blanket (UASB) reactor with energy recovery through biogas production and its conversion into heat and power in stationary engines and boilers, respectively. Based on the results obtained through the present case study, it was revealed that the adoption of UASB reactors by the paper mill industry could properly addresses the environmental concerns faced while could contribute to the national agenda favoring an increasing share of renewable energies in the country`s energy matrix. The financial analysis showed that the investment required for the implementation of UASB reactors within a biorefinery platform would be minor vs. the investment in the whole mill and would be returned in 6.4 yr with a high return on investment even when operated at half of operational capacity. Moreover, through the developed UASB reactor-based biorefinery, the Brazilian pulp and paper industry as a whole could avoid 1.06 ×105 CO2eq tons, effectively contributing to the decarbonization of the country`s economy.

Extensive studies on the treatment of pulp mill wastewater using aerobic granular sludge (AGS) technology

Aerobic granular sludge (AGS) offers the potential to degrade tannin/lignin found in pulp and paper wastewater (PPW). In this study, aerobic granules were cultivated in a sequencing batch reactor (SBR) with tannin/lignin present in the range of 50–200 mg/L. The mature granules were transferred to a real PPW wastewater system containing tannin/lignin concentration up to 500 mg/L. Biodegradation and biosorption were observed to be the two pathways for the removal tannin/lignin. Biosorption was a primary form of removal at lower concentrations, achieving 74% removal at 50 mg/L. The biosorption ability reduced to 58% removal at 200 mg/L. This reveals that biodegradation prevails at these higher concentrations. The Haldane kinetic parameters were: Vmax = 0.93 (g tannin/lignin/g VSS·day), Ks = 1910 mg/L, and Ki = 27 mg/L. Various adsorption kinetic models and isotherms were fitted to the system. The Langmuir isotherm coefficients were: (x/m) max = 21.5 (mg tannin/lignin/g SS), b = 0.00386 L/mg. The Freundlich isotherm had coefficients of n = 1.172, K = 0.1174. The study also delves into applying the technology towards real wastewater, achieving a COD removal of 79% and a tannin/lignin removal of 56%. Furthermore, experimental runs in warmer and more humid temperature conditions revealed higher removal efficiencies, achieving about 80% tannin/lignin degradation at a concentration of 130 mg/L. Results from this study will help ascertain an appropriate design protocol for full-scale industrial applications.

Study of the impacts of process changes of a pulp and paper mill on aerated stabilization basin (ASB) performance

A laboratory scale (LS) and a field-based pilot plant (PP), designed to simulate aerobic stabilization basin (ASB) operation, were utilized to assess the potential impacts of changes in pulp and paper (P&P) mill operations on full-scale (FS) ASB performance. Two stages of investigation were conducted. The first was undertaken to determine the potential of pre-alum treatment of pulp mill wastewaters on ASB performance. The second investigation was conducted to assess ASB performance where wastewaters transitioned from being coagulated pulp and paper mill wastewaters to paper mill wastewaters only. Simulation ASB performance was assessed based on removals of BOD5, colour, UV@254 nm and nutrients [total phosphorus (TP) and nitrogen compounds (TN)]. Pre-alum treatment of pulp mill wastewaters with subsequent ASB treatment following mixing with paper mill wastewaters showed high percentage removals of BOD5. Despite low TP concentrations (≤0.05 mg/L) and low nutrient to BOD5 ratios of wastewaters in the LS-ASB trial, the high % BOD5 removal indicated recycling of nutrients from sludge [sourced from the FS-ASB]. Despite coagulation of pulp mill wastewater being performed using a very high alum dose (∼2000 mg/L) to remove colour and its precursors, colour formation remained high throughout the simulated ASB trials. Simulation of discontinuation of pulping indicated that colour would reduce rapidly to low levels in ASB wastewaters, but that TP and TN concentrations would persist for longer periods of time and decline slowly. Survey data of water qualities of the FS-ASB system obtained before, during and 2 years after discontinuation of pulping are presented.

Influence of Organic Loading Rates (OLR) in Treatment of Pulp and Paper Mill Wastewater with Hybrid Upflow Anaerobic Sludge Blanket Reactor (HUASBR) with Hexagonal Polypropylene Inert Material

Abstract The present work illustrates the effective treatment of raw pulp and paper mill effluent using a model hybrid upflow anaerobic sludge blanket reactor (HUASBR). The physico-chemical and biological characteristics of wastewater were observed to be critical from the pollution potential aspect. The design features of model HUASBR had a respective total and effective working capacity of 7.5 and 6.5l, together with 25 cm depth of packing by polypropylene hexagonal inert material at the top of the reactor. Start-up of the reactor was carried out using an inoculum mixture containing rumen liquid of goat and cow dung slurry at an appropriate ratio of 3 : 1(v/v). Also, the reactor was effectively started up at the end of 36 days. Based on the performance of model HUASBR, under the respective variations of organic loading rates (OLRs) of 1, 2 and 4 kg COD m−3 d−1, the stepwise COD removals were found to be about 41, 69 and 87%. However, a hydraulic loading rate (HRT) of 20 h was appropriately maintained throughout the studies.

Application of response surface methodology as a new PID tuning method in an electrocoagulation process control case.

In this work the application of response surface methodology (RSM) to proportional-integral-derivative (PID) controller parameter tuning for electrocoagulation (EC) treatment of pulp and paper mill wastewater was researched. Dynamic data for two controlled variables (pH and electrical conductivity) were obtained under pseudo random binary sequence (PRBS) input signals applied to manipulated variables (acid and supporting electrolyte flow rates). Third order plus time delay model parameters were evaluated through System Identification Toolbox™ in MATLAB®. Four level full factorial design was applied to form a design matrix for three controller tuning parameters as factors and to evaluate statistical analysis of the system in terms of integral of square error (ISE), integral of absolute error (IAE), integral of time square error (ITSE) and integral of time absolute error (ITAE) performance criteria as response. Numerical values of the responses for the runs in the design matrices were determined using closed-loop PID control system simulations designed in Simulink®. Optimum proportional gain, integral action and derivative action values for electrical conductivity control were found to be 1,500 s, 0 s and 16.4636 s respectively. Accordingly, the same optimization scheme was followed for pH control and optimum controller parameters were found to be -8.6970 s, 0.0211 s and 50 s, respectively. Theoretically optimized controller parameters were applied to batch experimental studies. Chemical oxygen demand (COD) removal efficiency and energy consumption of pulp and paper mill wastewater treatment by EC under controlled action of pH at 5.5 and electrical conductivity at 2.72 mS/cm was found to be 85% and 3.87 kWh/m3 respectively. Results showed that multi input-multi output (MIMO) control action increased removal efficiency of COD by 15.41% and reduced energy consumption by 6.52% in comparison with treatment under uncontrolled conditions.

Effect of process control on optimization of pulp and paper mill wastewater treatment by electrocoagulation

Abstract The objective of this study was to determine the effect of electrical conductivity, pH and temperature which were kept constant during treatment via an advanced control strategy on chemical oxygen demand, color, turbidity and total suspended solids removal and energy consumption. Central Composite Design matrices were formed for aluminum and iron electrode systems separately with different combinations of 5 independent variables (electrical conductivity, pH, temperature, current intensity and electrolysis time). Obtained results revealed that aluminum electrode system was found to be more effective than iron electrode system under controlled conditions. Comparison of uncontrolled and controlled studies at optimum values of aluminum electrode system showed an increase by 31.67% in chemical oxygen demand removal and a decrease by 48.30% in energy consumption under controlled case. Results indicated that constant electrical conductivity, pH and temperature during electrocoagulation process of pulp and paper mill wastewater by means of a controller enhanced treatment efficiency.

Separation of pollutants from pulp mill wastewater by electrocoagulation

The paper and pulp mill industry is facing major problems in the disposal of wastewater generated from bleaching and pulping processes. Hence, effective treatment of pulp and paper mill wastewater is still a challenging task. In view of these factors, a research study was undertaken to investigate the feasibility of electrocoagulation process for the treatment of paper mill wastewater. The studies were conducted in an EC reactor of 1.50 L capacity with aluminium electrodes. The effects of operating parameters such as pH, current density, electrolysis duration and applied voltage on turbidity, TOC and COD removal efficiency have been investigated. The maximum COD, turbidity and total organic carbon (TOC) removal efficiencies of 89%, 96% and 72% respectively were obtained at pH 7 when the applied voltage was 12 V at electrolysis duration of 40 minutes. The specific energy consumption for the electrochemical treatment of a paper and pulpmill wastewater was estimated.

Separation of pollutants from pulp mill wastewater by electrocoagulation

The paper and pulp mill industry is facing major problems in the disposal of wastewater generated from bleaching and pulping processes. Hence, effective treatment of pulp and paper mill wastewater is still a challenging task. In view of these factors, a research study was undertaken to investigate the feasibility of electrocoagulation process for the treatment of paper mill wastewater. The studies were conducted in an EC reactor of 1.50 L capacity with aluminium electrodes. The effects of operating parameters such as pH, current density, electrolysis duration and applied voltage on turbidity, TOC and COD removal efficiency have been investigated. The maximum COD, turbidity and total organic carbon (TOC) removal efficiencies of 89%, 96% and 72% respectively were obtained at pH 7 when the applied voltage was 12 V at electrolysis duration of 40 minutes. The specific energy consumption for the electrochemical treatment of a paper and pulpmill wastewater was estimated.

BIOCONVERSION OF CELLULOSE INTO HYDROGEN, BIOGAS AND ORGANIC ACIDS USING MICROBIAL CONSORTIUM FROM A PULP AND PAPER MILL WASTEWATER TREATMENT PLANT

This study evaluated the potential of a microbial consortium collected from a pulp and paper mill wastewater treatment plant (WWTP) for converting cellulose to hydrogen, biogas and organic acids. Fermentation tests were conducted in batch reactors fed with different concentrations of cellulose as substrate: (C1) 2.0 g L -1; (C2) 5.0 g L -1 and (C3) 10.0 g L -1. The parameters investigated were hydrogen, biogas, organic acids, carbohydrates and pH. The maximum hydrogen production was 14.77, 39.25 and 22.53 mmol L -1, and the maximum methane was 4.40, 3.72 and 9.56 mmol L -1, for C1, C2 and C3, respectively. Butyric acid was the main metabolite generated, with maximum concentrations of 2.2, 1.8 and 2.2 g L -1 for C1, C2 and C3, respectively. The decrease in hydrogen production was accompanied by the production of methane, acetic acid and hydrogen sulfide in the three tests, probably related to hydrogenotrophic methanogenesis, homoacetogenesis and sulfidogenesis, respectively. The phylogenetic characterization of the bacterial community was performed by cloning and sequencing analysis. The microorganisms identified in the consortium were similar (> 95%) to Clostridium sp., Klebsiella sp., Routella sp. and Desulfovibrio sp. These genera were associated with hydrogen production, degradation of cellulosic substrates, and/or hydrogen-consuming microorganisms.

MIMO control application for pulp and paper mill wastewater treatment by electrocoagulation

MIMO control application for pulp and paper mill wastewater treatment by electrocoagulation

Enhanced Methane Yields in High-Solids Anaerobic Digestion Through Inoculation with Pulp and Paper Mill Sludge

High-solids anaerobic digestion (HS-AD) is used to recover energy and nutrients from the organic fraction of municipal solid waste. However, the low degradability of lignocellulosic wastes, such as yard wastes, limits the rate and extent of methane production from this process. This study investigated the potential to enhance methane yields from lignocellulosic waste during HS-AD through inoculation with granular anaerobic digester sludge from pulp and paper mill wastewater treatment systems (P&P sludge). P&P sludge contains microbial populations that are acclimated to a lignin-rich waste stream and has been shown to enhance methane production from agricultural residues. In this study, side-by-side bench-scale HS-AD experiments were carried out with yard waste inoculated with P&P sludge and domestic wastewater anaerobic digester (WW-AD) sludge. Average methane yield with the P&P inoculation strategy reached 100.2 ± 2.4 L CH4/kg volatile solids (VS), a 72.7% enhancement compared with WW-AD sludge (58.1 ± 1.2 L CH4/kg VS) over 106 days of batch digestion under mesophilic conditions. Trends in evolution of leachate volatile fatty acid and total ammonia nitrogen concentrations suggested that hydrolysis was accelerated in the P&P-inoculated digesters, causing methanogenesis to become rate limiting. Additional experiments were carried out to determine if the enhancement could be sustained through inoculation of fresh yard waste with digestate from the initial digesters, resulting in a 68.5% enhancement of methane yield. Although observed improvements are comparable to certain pretreatment methods, inoculation with sludge from the pulp and paper industry could be a low cost and less resource-intensive alternative to pretreatment and improve the overall sustainability of HS-AD processes.

Efficiency evaluation of the membrane/AOPs for paper mill wastewater treatment

ABSTRACTThe treatment of pulp and paper mill wastewater by combining an ultrafiltration (UF) membrane and advanced oxidation processes (AOPs) was investigated at a bench scale. In the present study, the effects of impressive parameters on membrane fouling such as CaCl2 (mg/L), pH, and temperature (°C) were studied using response surface methodology (RSM). According to the results yielded, at the temperature of 45°C, pH of 10 and CaCl2 concentration of 400 mg/L, the fouling reached its minimum (32%). Therefore, scanning electron microscopy (SEM) analyses showed that the average thickness of cake layer on the UF surface decreased from approximately 75.37 µm to 11.38 µm by optimizing the operating conditions. The results showed the UF permeate quality is not sufficient. Thus, AOPs applied for permeate. In this way, the performance of sulfate and hydroxyl radicals, generated by the activation of oxidants, such as persulfate () and H2O2, by Fe(II) for removal efficiencies was examined. Accordingly, under the optimum conditions of Filtration/Fenton ([H2O2] = 15 mM, [Fe(II)] = 6 mM, pH = 3), the removal efficiency of chemical oxygen demand (COD), UV254, and UV280 was 95.02%, 86.74%, and 87.08%, respectively. This is while, in the optimum conditions of Filtration//Fe(II) ([] = 7 mM, [Fe(II)] = 2 mM and pH = 6), the removal efficiency of COD, UV254, and UV280 reached 94.96%, 92.04%, and 90.16%, respectively. This is indicative of the fact that the process of Filtration//Fe(II), with a lower oxidant and catalyst concentration and pH close to the neutral range is more efficient than that of Filtration/Fenton.

Adding Growth-Promoting Ingredients in Activated Sludge Process as a Troubleshooting Strategy for Pulp and Paper Mill Wastewater Treatment

The activated sludge process is a well-established technology in the secondary treatment of pulp and paper mill wastewater. Maintaining the activities of microorganisms and allowing them to thrive, metabolize, and grow robustly is essential for efficient biological reactions. To this end, a scientific formulation of growth-promoting ingredients (containing stimulants, buffers, micronutrients, etc) provides a useful strategy for addressing the impact of fluctuations in process conditions involved in the pulp and paper production. Lots of potential exists in terms of the use of these “smart” ingredients to meet stricter discharge limits.

Application of modified bentonite granulated electrodes for advanced treatment of pulp and paper mill wastewater in three-dimensional electrode system

Two types of granular electrodes (cetyl trimethyl ammonium bromide modified bentonite (CTAB-bent) and hydroxy-aluminum pillared organic bentonite (OH-Al-CTAB-bent)) were prepared and form a three-dimensional (3-D) electrode system with general electrode plates to dispose the pulp and paper secondary wastewater deeply of paper mills. Then XRD, FTIR and SEM spectroscopy analysis were applied to characterize the feature of the electrodes. The removal efficiency of the chemical oxygen demand (COD) and color of the effluent after treatment was investigated. It was found that the removal efficiency of COD and color depended on the reaction time, current density, amount of granular electrode, the airflow and the run times. The results proved that the 3-D electrode system exhibited high efficiency in the removal of COD and color. Under the optimum conditions, the COD could be degraded from initial 256mg/L to 40mg/L, that was, 84.3% of COD were removed. And the removal efficiency of color could reach 93%. So the secondary wastewater treated advanced could meet the discharge standard (GB3544-2008). Finally, the possible reaction mechanism of organic pollutants degradation in 3-D electrode system was expatiated.

Chitin: a potential new alternative nitrogen source for the tertiary, algal-based treatment of pulp and paper mill wastewater

Every day, pulp and paper mills in the USA discharge millions of liters of wastewater. Primary and secondary treatment of this wastewater often enriches it with phosphorus, resulting in uncontrolled eutrophication of receiving water bodies. A new method of tertiary wastewater treatment uses controlled growth of algae in a photobioreactor to sequester phosphorus into algal biomass, which is then harvested. This typically requires addition of a nitrogen fertilizer (nitrate, ammonium, or urea) to the water. We show on the laboratory scale that chitin can be used as an alternative source of nitrogen for the tertiary treatment of pulp mill wastewater using algae. We demonstrate that phosphorus can be efficiently removed from pulp wastewater using algae and chitin. Furthermore, phosphorus removal with chitin did not result in an increase in dissolved nitrogen in the wastewater because it is insoluble, unlike conventional nitrogen fertilizers. Despite its insolubility, it has recently been found that many diverse algae and cyanobacteria can use it as a source of nitrogen. Chitin has many advantages over conventional nitrogen fertilizers for use in wastewater treatment technologies. It is the second-most abundant natural polymer and is a waste product of the shellfish industry. Chitin is sustainable, inexpensive, and carbon neutral. Thus, chitin improves the sustainability and carbon footprints associated with water treatment, while the production of commercially attractive algal biomass helps to offset costs associated with the water treatment system itself.

Continuous electrocoagulation treatment of pulp and paper mill wastewater: operating cost and sludge study

Schematic view of continuous electrocoagulation set up.

Effects of black liquor shocks on activated sludge treatment of bleached kraft pulp mill wastewater

Kraft pulp mills use activated sludge systems to remove organic matter from effluents. Process streams may appear as toxic spills in treatment plant effluents, such as black liquor, which is toxic to microorganisms of the activated sludge. The present study evaluates the effects of black liquor shocks in activated sludge systems. Four black liquor shocks from 883 to 3,225 mg chemical oxygen demand−COD L−1 were applied during 24 hours in a continuously operating lab−scale activated sludge system. Removal efficiencies of COD, color and specific compounds were determined. Moreover, specific oxygen uptake rate (SOUR), sludge volumetric index (SVI) and indicator microorganisms were evaluated. Results show that the addition of black liquor caused an increase in COD removal (76−67%) immediately post shock; followed two days later by a decrease (−19−50%). On the other hand, SOUR ranged between 0.152 and 0.336 mgO2 g−1 volatile suspended solids−VSS• min−1 during shocks, but the initial value was reestablished at hour 24. When the COD concentration of the shock was higher than 1,014 mg/L, the abundance of stalked ciliates and rotifers dropped. Finally, no changes in SVI were observed, with values remaining in the range 65.8−40.2 mL g−1 total suspended solids−TSS during the entire operating process. Based on the results, the principal conclusion is that the activated sludge system with the biomass adapted to the kraft pulp effluent could resist a black liquor shock with 3,225 mgCOD L−1 of concentration during 24 h, under this study's conditions.

Biodegradation of Kraft Lignin by a Bacterial Strain <i>Sphingobacterium</i> sp. HY-H

A lignin-degrading bacterium was isolated on mineral salt medium amended by lignosulfonate (L-MSM) agar from the activated sludge of a pulp and paper mill wastewater treatment plant and identified as Sphingobacterium sp. HY-H by biochemical tests and 16S rRNA gene sequencing. The maximum kraft lignin (KL) degradation capability of strain HY-H was determined to be 28.2% on a COD basis under the optimal conditions of pH 7.0, temperature 30°C, and KL to nitrogen (as NH4Cl) ratio of 2 by mass. Moreover, growth kinetic studies showed the KL tolerance of strain HY-H was relatively high and the analysis of KL degradation products by GC-MS revealed the formation of low-molecular-weight aromatic compounds (LMWACs), such as guaiacol, vanillin and vanillyl alcohol, indicating that the strain HY-H can oxidize guaiacyl (G) units and syringyl (S) units in lignin structure. In addition, some low molecular ketone compounds such as 4-hydroxy-2-butanone and methyl vinyl ketone were detected in the inoculated sample after 48h, further validating the partial but possible degradation of KL by strain HY-H.

Treatment of pulp mill wastewater by Cryptococcus podzolicus and solar photo-Fenton: A case study

Abstract This study evaluated a combination of biological and physical–chemical processes for pulp mill wastewater (PMW) treatment. Biological tests were performed with various yeasts to find out their capacity for growth at different temperatures in the effluent under study. Of the 8 yeast isolates, Cryptococcus podzolicus (AGG 691) proved to be the most appropriate for the aims pursued. After 32 h of incubation, the AGG 691 monoculture had removed 68% of the chemical oxygen demand (COD) and 27% of total polyphenols (TP). This was followed by evaluation of a physical–chemical polishing step. First, coagulation/flocculation was evaluated. Since this was found to be ineffective, two Advanced Oxidation Processes (AOPs), dark-Fenton and solar photo-Fenton, were then studied. Solar photo-Fenton experiments were performed with 10, 20 and 50 mg/L concentrations of Fe2+. Although all the solar photo-Fenton experiments showed over 90% dissolved organic carbon (DOC) removal, the experiment with 10 mg Fe2+/L was selected as the best treatment option considering the lowest consume of iron and H2O2. Treatment with Cr. podzolicus (AGG 691) yeast followed by solar photo-Fenton was able to ensure that pulp mill wastewater discharged into natural waters met legal requirements.

Experimental design of wastewater treatment with electro-coagulation

Purpose – The purpose of this paper is to investigate the batch treatment of pulp and paper mill wastewater using electro-coagulation (EC). Design/methodology/approach – Statistical experimental design was used to investigate the effect of initial pH, current density and temperature. Experiments were planned to obtain the maximum amount of information in the fewest number of runs. Minimum-maximum values of current density, initial pH, temperature of medium were selected as 9-25 mA/cm2, 5-9, 25-50°C, respectively. A total number of 20 experiments including eight factorial points, six axial points and six replicates in centre points were carried out and experimental data were collected. Optimum operating parameters were determined by evaluating experimental results in MATLAB 7.9®. Findings – According to the results, the optimum values of current density, initial pH and temperature of medium are determined as 14.12 mA/cm2, 8.22 and 34.21°C, respectively. Practical implications – Many researches about different techniques including physical, chemical and biological methods have been done on the subject of pulp and paper wastewater treatment. In physical and chemical processes low molecular weight compounds are not removed efficiently, also these methods are quite expensive. Electrochemical degradation has an advantage of removing even the smallest colloidal particles compared with traditional flocculation and coagulation. Originality/value – Complete removal of pollutants, less sludge generation, simple process design and easy operation are standard features of the EC and it comes forward as one of the promising techniques.