Combined chemical biological treatment of bleached eucalypt kraft pulp mill effluent.

Effectiveness of ozonation before and after biological treatment for removal of recalcitrant organic matter in bleached kraft pulp effluents was compared. Two industrial ECF bleached eucalypt kraft pulp effluents (E1 and E2) were pretreated with 100 mg O3/L. Raw and pretreated effluents were treated biologically in bench-scale sequencing batch reactors, under constant conditions. Following biological treatment, effluents were post-treated with 100 and 200 mg O3/L. Effluent pretreatment increased effluent biodegradability by 10% in E1 and 24% in E2. Combined O3-biological treated led to small but significant increases in COD, BOD and lignin removal over biological treatment alone, but pretreatment had no significant effect on effluent colour and carbohydrate removal. Ozone pretreatment did not affect biological activity during treatment of effluent E1 but resulted in a 38% lower specific oxygen uptake rate in effluent E2. At an equivalent dose of 100 mg/L, pre-ozonation produced better quality effluent than post-ozonation, especially with regard to COD and colour. Likewise, when an equivalent dose of 200 mg/L was applied, splitting the dose equally between pre- and post-treatments was more efficient than applying the entire dose in the post-treatment. The potential for combined chemical-biological treatment to improve effluent quality has been confirmed in this study.     

Multi-component kinetics of activated sludge treatment of bleached kraft mill effluent.

This study investigated the discrepancies between the BOD removal rates measured during short term assays and those measured during continuous activated sludge treatment of bleached kraft mill effluent (BKME). A combination of batch tests and fed batch tests with oxygen uptake rate (OUR), chemical oxygen demand (COD), biochemical oxygen demand (BOD), and mixed liquor volatile suspended solids (MLVSS) measurements were used to characterize the degradation rates for the activated sludge treatment of BKME and to divide the soluble readily biodegradable substrate into two to five separate fractions based on biodegradation rates. The removal rates varied by over an order of magnitude between the most readily degradable substrates (1 x 10(-3) mg COD/mg MLVSS minute), and the more slowly degradable substrates (2 x 10(-5) mg COD/mg MLVSS minute). If the readily biodegradable fraction of BKME was modeled as one substrate, initial rate kinetic measurements from batch tests were heavily influenced by the fractions with the greatest degradation rates, while any remaining BOD in the treated effluent was predominantly from the slowly degradable fraction, giving inconsistent results. Taking the multi-component nature of the wastewater into account, batch test results can be used to predict fed-batch and continuous activated sludge reactor performance.     

A comparison of conventional activated sludge and low sludge production strategies for advanced treatment of kraft pulp mill effluent.

Parallel laboratory investigations were conducted to examine aspects of two distinct but related bioprocess strategies for low sludge production in the treatment of the same TCF kraft pulp mill effluent. The purpose of this article has been to compare the performance results from these two bench-scale trials with respect to nutrient demands, nutrient discharge, COD removal, and waste sludge characteristics. The LSP (Low Sludge Production) process can be used to significantly reduce sludge yield with excellent sludge characteristics. These sludge characteristics seemed to be related to elevated protozoan grazing pressures. The BAS (Biofilm-Activated Sludge) process achieves similar reduced sludge yields and sludge characteristics while at the same time significantly reducing the nutrient demands and discharge levels. For both LSP and BAS process optimization, the selector nutrient loading is critical to the overall process performance. Selector nutrient requirements are distinct from the overall process nutrient requirements.     

Removal of colour from a kraft pulp and paper mill effluent in Kenya using a combination of electrochemical method and phosphate rock.

A study was undertaken to remove colour from a kraft mill's treated effluent in Kenya and determine the suitability of phosphate rock to replace wood ash during the electrochemical process. The electrochemical method alone, electrochemical combined with alum (ELCAL), wood ash leachate (ELCAS) and phosphate rock (ELPHOS) solutions at a rate of 165 to 1000 g/m3 were tested. Effluent characteristics were determined after complete removal of colour. Same reduction rates of TS (85%) and TSS (89%) were recorded by ELCAS and ELPHOS. However, ELPHOS removed more COD (86 to 91%) and more BOD (85 to 92%) than ELCAS. Furthermore, the pH of ELPHOS treated solution was 9.3, within the Kenya Local Government's allowable limit. Power reduction with ELCAS and ELPHOS varied between 53 to 73% and 49 to 69% respectively but the difference was not statistically significant. Overnight aeration further improved the quality of ELCAS and ELPHOS treated effluent, reducing BOD and COD values to 0 mg/l. ELPHOS cost ($0.29/m3) was nevertheless three times higher than that of ELCAS ($0.10/m3), mainly because of free wood ash. ELPHOS did not also increase effluent phosphorus. It was therefore recommended that various ways be explored in making ELPHOS more economical to replace ELCAS.     

Multivariate statistical analysis of a high rate biofilm process treating kraft mill bleach plant effluent.

This study reports on a multivariate analysis of the moving bed biofilm reactor (MBBR) wastewater treatment system at a Canadian pulp mill. The modelling approach involved a data overview by principal component analysis (PCA) followed by partial least squares (PLS) modelling with the objective of explaining and predicting changes in the BOD output of the reactor. Over two years of data with 87 process measurements were used to build the models. Variables were collected from the MBBR control scheme as well as upstream in the bleach plant and in digestion. To account for process dynamics, a variable lagging approach was used for variables with significant temporal correlations. It was found that wood type pulped at the mill was a significant variable governing reactor performance. Other important variables included flow parameters, faults in the temperature or pH control of the reactor, and some potential indirect indicators of biomass activity (residual nitrogen and pH out). The most predictive model was found to have an RMSEP value of 606 kgBOD/d, representing a 14.5% average error. This was a good fit, given the measurement error of the BOD test. Overall, the statistical approach was effective in describing and predicting MBBR treatment performance.     

Application of statistical experimental design to the treatment of bleaching kraft mill effluent using a mediated free radical system.

The aim of this work was to evaluate the effect of chelator mediated-Fenton reaction (CMFR) on the chemical oxygen demand (COD) removal from bleaching kraft mill effluent. Effluent treatments were carried out to study the effect of the chelator 3, 4-dihydroxyphenylacetic acid (DOPAC), Fe3+ and H2O2 concentrations on COD removal. For optimization of COD removal, the methodology of statistical experimental design was employed. The estimated second-order polynomial multiple regression model predicts a maximum COD removal of 75.5% (COD/COD0 = 0.245) at the confidence level of 95%. Analysis of variance (ANOVA) showed a good coefficient of determination (R2) value of 0.90, thus ensuring a satisfactory adjustment of the second-order regression model with the experimental data. Indeed, CMFR proved to be a potential process to treat industrial effluents characterized by its high COD.     

Organic matter balance in ECF kraft mill fiberline.

Organic matter balances of an ECF kraft mill fiberline were studied in three different operational conditions of the oxygen delignification stage by implementing mill measurements, collecting routine mill data and combining them in a modified PROCELL steady state model. Dissolved volatile solids was the basic measurement for organic matter in liquid streams. Normal operation of the O2D0E(O)D1E(OP)D2 fiberline was described successfully. It was also possible to describe exceptional operating situations in the oxygen delignification stage and their effects on other parts of the production process reasonably well in order to focus studies on aspects requiring further attention. The existence of organic matter lost through complete degradation and volatile organic compounds in unit processes as well as its sensitivity to yield and operational situations is shown. The different perspectives of pulp production and wastewater treatment can be brought closer to each other using the approach in this study. The variation in the fractions discharged to wastewater treatment, although a relatively small share of the overall organic matter balance, will continue to become more important also for pulp production when effluent streams are increasingly turned back to the production line through further closure. Studies like the one presented here, can contribute to the evaluation of this development.     

The impact of cleaner processing on nutrient availability in the bleached kraft industry.

The pulp and paper industry has invested heavily over recent years in cleaner processing, to reduce losses and minimise its impact on the environment. Over the past fifteen years, a New Zealand integrated bleached kraft mill has undergone a comprehensive programme of upgrades to increase production, reduce water consumption and streamline its biological treatment process. Whilst the overall discharge of contaminants from the site decreased, the treatment system performance did not show a concurrent improvement as may have been expected. Reduced BOD removal, low dissolved oxygen levels, and poor solids settlability were symptomatic of phosphorus limitation in the aerated lagoon treatment system. The wastewater entering the system was found to be phosphorus limited at a BOD:P ratio of 100:0.2. Mono-ammonium-phosphate was supplemented, at approximately 30 kg P/d, to raise the phosphorus levels to a BOD:P ratio of 100:0.3. Treatment efficiencies improved very quickly after phosphorus dosage, with a 50% reduction in BOD and TSS discharge, a significant increase in dissolved oxygen levels, and improved BOD removal (85% to 93%). This case study demonstrates that whilst more closed operation can result in reduced discharge of organic loads, there may be negative impacts on the availability of nutrients for balanced biological growth.     

A filtrate phase perspective to organic matter balance in ECF bleached kraft fiberline.

In the process of making high quality pulp from wood chips, much water will continuously be needed. The fate of the used water with the organic and inorganic impurities remains optional. Mills with zero liquid effluent have been mentioned as the target in environmental loading minimization of pulp and paper mills with hardly any debate. To avoid inappropriate solutions when approaching this target, thorough knowledge of loading element behavior in liquid streams of production processes should be available before decisions are made for development alternatives. Based on empirical measurements of dissolved organic matter (DOM) in liquid streams of fiberline and utilizing them together with routine mill data in process simulation, this study aims at mapping DOM and its fate in elemental chlorine free (ECF) softwood kraft pulp production. The results of this study act as a demonstration for determining the essential fates and their quantities in the ECF fiberline.     

Advanced treatment by anaerobic process followed by aerobic membrane bioreactor for effluent reuse in paper mill industry.

The operation of an activated sludge process at a paper mill (AIPM) in Hedera, Israel, was often characterized by disturbances. As part of a research and development project, a study on new biological treatment was initiated. The study included the operation of three pilot units: a. anaerobic treatment by upflow anaerobic sludge blanket (UASB); b. aerobic treatment by two pilot units including activated sludge and membrane bioreactor (MBR), which have been operated in parallel for comparison reasons. The pilot plant working on anaerobic treatment performed COD reduction from 2,365 to 755 mg/L, expressed as average values. Based on the pilot study, a full scale anaerobic treatment system has been erected. During a period of 100 days, after achieving steady state, the MBR system provided steady operation performance, while the activated sludge produced effluent characterized by oscillatory qualities. The following results, based on average values, indicate much lower suspended solids concentrations in the MBR effluent, 2.5 mg/L, as compared to 25 mg/L in the activated sludge. The ability to develop and maintain a concentration of over 11,000 mg/L of mixed liquor volatile suspended solids in the MBR enabled an intensive bioprocess at relatively high cell residence time. This study demonstrates that the anaerobic process, followed by aerobic MBR can provide effluent of high quality which can be considered for economic reuse in the paper mill industry.     

Modelling carbon oxidation in pulp mill activated sludge systems: calibration of Activated Sludge Model No 3.

Activated Sludge Model No 3 (ASM3) was chosen to model an activated sludge system treating effluents from a mechanical pulp and paper mill. The high COD concentration and the high content of readily biodegradable substrates of the wastewater make this model appropriate for this system. ASM3 was calibrated based on batch respirometric tests using fresh wastewater and sludge from the treatment plant, and on analytical measurements of COD, TSS and VSS. The model, developed for municipal wastewater, was found suitable for fitting a variety of respirometric batch tests, performed at different temperatures and food to microorganism ratios (F/M). Therefore, a set of calibrated parameters, as well as the wastewater COD fractions, was estimated for this industrial wastewater. The majority of the calibrated parameters were in the range of those found in the literature.     

Use of electrochemical oxidation process as post-treatment for the effluents of a UASB reactor treating cellulose pulp mill wastewater.

The main purpose of this study was to evaluate the performance of the electrochemical oxidation process as a post-treatment for the effluents of a bench-scale UASB reactor treating simulated wastewater from an unbleached pulp plant. The oxidation process was performed using a single compartment cell with two plates as electrodes. The anode was made of Ti/Ru0.3Ti0.7O2 and the cathode of stainless steel. The following variables were evaluated: current density (75, 150 and 225 mA cm(-2)) and recirculation flow rate in the electrochemical cell (0.22, 0.45 and 0.90 L h(-1)). The increase in current density from 75 to 225 mA cm(-2) did not increased the color removal efficiency for the tested flow rates, 0.22, 0.45 and 0.90 L h(-1), however the energy consumption increased significantly. The results indicated the technical feasibility of the electrochemical treatment as post-treatment for UASB reactors treating wastewaters from pulp and paper plants.     

Anaerobic degradation of palm oil mill effluent (POME)

The biodegradation characteristics of palm oil mill effluent (POME) and the related microbial community were studied in both actual sequential anaerobic ponds in Malaysia and enrichment cultures. The significant degradation of the POME was observed in the second pond, in which the temperature was 35-37 °C. In this pond, biodegradation of major long chain fatty acids (LCFA), such as palmitic acid (C16:0) and oleic acid (C18:1), was also confirmed. The enrichment culture experiment was conducted with different feeding substrates, i.e. POME, C16:0 and C18:1, at 35 °C. Good recovery of methane indicated biodegradation of feeds in the POME and C16:0 enrichments. The methane production rate of the C18:1 enrichment was slower than other substrates and inhibition of methanogenesis was frequently observed. Denaturing gradient gel electrophoresis (DGGE) analyses indicated the existence of LCFA-degrading bacteria, such as the genus Syntrophus and Syntorophomonas, in all enrichment cultures operated at 35 °C. Anaerobic degradation of the POME under mesophilic conditions was stably processed as compared with thermophilic conditions.     

Anaerobic treatment of pulp and paper mill effluents--status quo and new developments.

Since the early 1980s, anaerobic treatment of industrial effluents has found widespread application in the pulp and paper industry. Over 200 installations are treating a large variety of different pulp and paper mill effluents. Amongst various anaerobic systems the UASB and IC are the most applied anaerobic reactor systems. Anaerobic treatment is well feasible for effluents originated from recycle paper mills, mechanical pulping (peroxide bleached), semi-chemical pulping and sulphite and kraft evaporator condensates. The advantages of anaerobic pre-treatment are (1) net production of renewable energy (biogas), (2) minimized bio-solids production, (3) minimal footprint and (4) reduced emission of greenhouse gases. Via in-line application of anaerobic treatment in closed circuits (paper kidney technology) further savings on cost of fresh water intake and effluent discharge levies are generated.     

Evaluation of total phosphorus and total nitrogen methods in pulp mill effluents.

Under the Clean Water Action Plan, the US Environmental Protection Agency is requiring states to establish numeric criteria for phosphorus and nitrogen. In preparation for the development of nutrient criteria NCASI undertook a research project to conduct a comparative study of methods for the determination of total phosphorus and total nitrogen in pulp and paper mill matrices. This paper presents results of a single laboratory method evaluation and comparative study of digestion techniques and analytical methods for the determination of total phosphorus (TP) and total nitrogen (TN) in pulp and paper mill secondary treated effluents. Analytical methods included EPA Methods 365.2 and 365.4 for TP. TN and total kjeldahl nitrogen (TKN) methods included EPA Methods 351.2, 351.4, and 353.2. Examinations of sample preservation and storage stability were conducted. Substitution of mercuric sulfate with copper sulfate during block digestion resulted in higher blank levels and method detection limits. TP measurements using EPA Method 365.4 (autoanalyzer) were found to be accurate with a positive bias as determined using matrix spike experiments. Sample digestion by acidic persulfate oxidation or mercuric sulfate block digestion in conjunction with EPA Method 365.4 yielded low blank levels (averages of 0.01 and 0.02 mg/L, respectively), precision of 2.1 and 2.4% relative standard deviations, respectively, and accuracy expressed as an average recovery (%R) of 117% for both. EPA Method 351.2 (autoanalyzer) was more precise than EPA Method 351.4 (ammonia probe). Accuracy (%R) for EPA Method 351.2 ranged from 81 to 95%, depending on the digestion technique applied, and was 55% when EPA Method 351.4 was utilized. Investigation of a method utilizing basic to acidic persulfate oxidation for the simultaneous determination of TN and TP using only two analytical techniques was found to be effective at concentrations above 1 mg/L in pulp mill effluents.     

Disinfection and oxidation of sewage effluent water using ozone and UV technologies.

This study was aimed at exploring the reclamation of sewage treatment plant effluent water (SEW) as an alternative water resource. For the oxidation of SEW, an ozone-UV system, based on the results of the combined ozone/UV process performed in our previous study, was set up under practical conditions, including a series type, continuous mode, semi-pilot scale operation (1.5 m3/d). As a result, the serial contact of the ozone and UV reactors showed lower CODCr and TOC removal efficiencies. However, these were greatly enhanced by recycling the water flow of the ozone-UV system at 40Q, as a result of the improvements in the transferred ozone dose in the ozone reactor and the contact efficiency between photons and ozone in the UV reactor, which approached that achieved in the combined ozone/UV process. For the disinfection of SEW, carried out in a syringe-type batch reactor, the increase of instantaneous ozone demand (ozone ID) led to a higher inactivation efficiency, an increased UV transmittance due to ozonation, and an enhanced inactivation rate of E. coli in the UV reactor. Additionally, it was concluded that the ozone/UV process could overcome the limitations of the ozone alone and UV alone processes for the reclamation of sewage effluent water.     

Semi-continuous treatment of recalcitrant anaerobic effluent from pulp and paper industry using hybrid pellets of Trametes versicolor.

The objective of this work was to evaluate the semi-continuous post-treatment of anaerobically-pre-treated weak black liquor (anaerobic effluent, AnE) by aerobic post-treatment using hybrid pellets of Trametes versicolor. The latter consisted of fungus immobilized onto holm oak sawdust (mixed or double pellets) or a mixture of holm oak sawdust and powdered activated carbon (triple pellets). First, a semicontinuous experiment was run to compare the effectiveness of triple and mixed pellets in agitated flasks for 15 cycles of 7 days each. A second extended batch test was implemented with 500 mL AnE and triple pellets to give 400 mg fungal biomass; some units were spiked with protease inhibitor. In the first experiment, triple pellets displayed consistently higher removal efficiencies of pollutant parameters than double pellets (10 to 15% higher), although overall averages were moderate and no statistical significance to the difference could be set because of the noise of fluctuations. Periodic fluctuations of removal were characterized by three periods of approximately six cycles each with maximum removals occurring at cycles 3-4, 7-9, 13, and 14. Evaluating pooled removals of the latter cycles showed that triple pellets were significantly more effective than double pellets, with removal efficiencies as high as 47% of COD, colour, and absorbance at 254 nm (A254). In general, protease activity seemed to increase in the third period (last six cycles), whereas activities of MnP, LiP and Lac significantly decreased. In the second experiment, pollutant removals and enzymatic activities of triple pellets with protease inhibitor were significantly higher than those of units without added protease inhibitor. These results indicate that protease could be the main cause of periodic falls of pollutant removal efficiencies found in the first experiment.     

Treatment of paper mill effluent using an anaerobic/aerobic hybrid side-stream membrane bioreactor

This paper presents the design and operational performance data of an anaerobic/aerobic hybrid side-stream Membrane Bioreactor (MBR) process for treating paper mill effluent operated over a 6 month period. The paper mill effluent stream was characterized by a chemical oxygen demand (COD) range of between 1,600 and 4,400 mg/L and an average BOD of 2,400 mg/L. Despite large fluctuations in COD feed concentration, stable process performance was achieved. The anaerobic Expanded Granular Sludge Bed (EGSB) pre-treatment step effectively lowered the organic loading by 65 to 85%, thus lowering the MBR COD feed concentration to consistently below 750 mg/L. The overall MBR COD removal was consistent at an average of 96%, regardless of the effluent COD or changes in the hydraulic retention time (HRT) and organic loading rate (OLR). Combining a high-rate anaerobic pre-treatment EGSB with a Modified Ludzack-Ettinger (MLE) MBR process configuration produced a high quality permeate. Preliminary NF and RO results indicated an overall COD removal of around 97 and 98%, respectively.     

Performance of cellulose acetate - polyethersulphone blend membrane prepared using microwave heating for palm oil mill effluent treatment.

The objective of this research is to investigate the performance of blend cellulose acetate (CA)-polyethersulphone (PES) membranes prepared using microwave heating (MWH) techniques and then compare it with blend CA-PES membranes prepared using conventional heating (CH) methods using bovine serum albumin solution. The superior membranes were then used in the treatment of palm oil mill effluent (POME). Various blends of CA-PES have been blended with PES in the range of 1-5 wt%. This distinctive series of dope formulations of blend CA/PES and pure CA was prepared using N, N-dimethylformamide (DMF) as solvent. The dope solution was prepared by MW heating for 5 min at a high pulse and the membranes were prepared by phase inversion method. The performances of these membranes were evaluated in terms of pure water and permeate flux, percentage removal of total suspended solids (TSS), chemical oxygen demand (COD) and biochemical oxygen demand (BOD). The results indicate that blend membranes prepared using the microwave technique is far more superior compared to that prepared using CH. Blend membranes with 19% CA, 1-3% PES and 80% of DMF solvent were found to be the best membrane formulation.     

Treatment of an ECF effluent by combined use of activated sludge and advanced oxidation process.

The combined biological and chemical treatments of the cellulose effluents have been studied aiming to promote a more significant degradation of their recalcitrant compounds and to reduce their toxicity, as compared with the isolated treatments. In this work the effluent from acid stages of the ECF bleaching of Eucalyptus urograndis pulp was treated by using separately activated sludge and UV radiation and its combination. The treatment efficiency was evaluated by colour, total phenol, COD, BOD, UV spectroscopy, molar weight distribution and toxicity. The untreated effluent presented 587 +/- 18 CU, 19.3 +/- 0.6 mg.L(-1) of total phenol, 2246 +/- 137 mgO2.L(-1) of COD and 904 +/- 48 mgO2.L(-1) of BOD. It did not show acute toxicity to Escherichia coli, but presented chronic toxicity to Selenastrum capricornutum (EC50 = 25%). The sludge treatment resulted in a colour increasing of 42% and decreasing of total phenol, COD and BOD of 33%, 64% and 92%, respectively. The UV radiation treatment for 120 min resulted in a decrease of colour, total phenol, BOD and COD of 70%, 43%, 62% and 43%, respectively. The combined treatment promoted an expressive decrease for colour and total phenol. The UV absorption indicated a degradation of the aromatic compounds. The biological treatment did not remove chronic toxicity and after UV radiation treatment, a 10 times improving toxicity was noticed.