Kraft Pulp Mill Wastewater Research Articles

Hybrid solar drying of sludge from kraft pulp mills

Abstract Sludge generated from kraft pulp mill wastewater treatment plants (WWTPs) is typically non-inert solid waste and is commonly disposed of in landfills. In this study, a novel approach for repurposing WWTP sludge from a kraft pulp mill in Brazil for energy generation was assessed. With the global cellulose market projected to reach $ 61 billion by 2033, there is a growing need for sustainable energy solutions and disposal of associated industrial byproducts. This study investigated the performance of a hybrid active solar dryer for reducing the moisture content of sludge to enhance the feasibility of sludge burning in a biomass boiler. Through rigorous experimentation and design of experiments (DOE) planning, optimal parameters for the hybrid dryer were determined, specifically, a volumetric airflow rate of 1.1 m/s and an entrance temperature of approximately 51 °C. This innovative approach not only addresses the environmental concerns associated with sludge disposal, but also contributes to the broader goal of advancing sustainable technologies in the midst of global energy challenges.

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.

Simultaneous precipitation of phosphorus in a kraft pulp mill wastewater treatment plant

Simultaneous precipitation (SP) using iron sulfates in the secondary treatment of elemental chlorine-free (ECF) kraft pulp mill wastewater was studied. In short-term pilot plant studies phosphorus reduction was improved from 58% up to 81% by adding 10 mg(Fe)/L ferrous sulfate in the activated sludge (AS) process. The phosphorus reduction in full-scale experiment was about 80% when less than 10 mg(Fe)/L was fed in with the influent of the AS plant. The reduction of phosphorus decreased with the dose of iron during the three month experiment. No notable change in either chemical oxygen demand (COD) or adsorbable organic halogen (AOX) reduction nor in the properties of sludge settling were observed during this SP experiment. Furthermore, no problems in sludge treatment due to increased iron concentrations in the waste sludge were reported. SP offers a simple way to decrease phosphorus discharges from AS plants instead of reliance on more expensive tertiary treatments.

Advanced oxidation process H2 O2 /UV combined with anaerobic digestion to remove chlorinated organics from bleached kraft pulp mill wastewater

This study investigated the application of an advanced oxidation process combining hydrogen peroxide with ultraviolet radiation (H2 O2 /UV) to remove recalcitrant compounds from Kraft bleaching effluent. Anaerobic pre-treatment was performed to remove easily degraded organics using a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. Bleaching plant effluent was treated in the HAIB reactor processed over 19 h of hydraulic retention time (HRT), reaching the expected removal efficiencies for COD (61 ± 3%), TOC (69 ± 9%), BOD5 (90 ± 5%) and AOX (55 ± 14%). However, the anaerobic treatment did not achieve acceptable removal of UV254 compounds. Furthermore, there was an increase of lignin, measured as total phenols. The H2 O2 /UV post-treatment provided a wide range of removal efficiencies depending on the dosage of hydrogen peroxide and UV irradiation: COD ranged from 0 to 11%, UV254 from16 to 35%, lignin from 0 to 29% and AOX from 23 to 54%. All peroxide dosages applied in this work promoted an increase in the BOD5 /COD ratio of the wastewater. The experiments demonstrate the technical feasibility of using H2 O2 /UV for posttreatment of bleaching effluents submitted to anaerobic pre-treatment.

Reduced Sulfur Compound Emissions from Kraft Pulp and Paper Mill Wastewater Treatment Plants

Reduced Sulfur Compound Emissions from Kraft Pulp and Paper Mill Wastewater Treatment Plants

Size fractionation of wood extractives, lignin and trace elements in pulp and paper mill wastewater before and after biological treatment

Integrated kraft pulp and paper mill wastewater was characterized before (influent) and after (effluent) the activated sludge process by microfiltration (8, 3, 0.45 and 0.22 μm) and ultrafiltration (100, 50, 30 and 3 kDa) into different size fractions. Wood extractives, lignin, suspended solids and certain trace elements were determined in each fraction. Forty four percent of the resin and fatty acids in the influent (12.8 mg/L) occurred in particles (>0.45 μm), 20% as colloids (0.45 μm–3 kDa) and 36% in the <3 kDa fraction. The corresponding values for sterols (1.5 mg/L) were 5, 46 and 49%. In the effluent, resin and fatty acids (1.45 mg/L) and sterols (0.26 mg/L) were mainly present in the <3 kDa fraction, as well as a small proportion in particles. β-sitosterol was present in particles in the effluent (88 ± 50 μg/L). Lignin in the influent was mainly in the colloidal and <3 kDa fractions, whereas in the effluent it was mainly in the <3 kDa fraction. Thus the decrease of lignin in the biological treatment was concentrated on the colloidal fraction. In the influent, Mn, Zn and Si were mainly present in the <3 kDa fraction, whereas a significant proportion of Fe and Al were found also in the particle and colloidal fractions. In the effluent, Fe and Al were mainly present in the colloidal fraction; in contrast, Mn, Zn and Si were mainly in the <3 kDa fraction. The results indicated that the release of certain compounds and elements into the environment could be significantly decreased or even prevented simply by employing microfiltration as a final treatment step or by enhancing particle removal in the secondary clarifier.

Reduced Sulfur Compound and Methane Emissions from Kraft Pulp and Paper Mill Wastewater Treatment Plants

Reduced Sulfur Compound and Methane Emissions from Kraft Pulp and Paper Mill Wastewater Treatment Plants

Biodegradation of Dibenzofuran and Dioxins by Pseudomonas Aeruginosa and Xanthomonas Maltophilia

This study was aimed at finding microorganisms capable of biodegrading dioxins efficiently to develop a biotechnological treatment for decomposition of dioxins. Dibenzofuran (DBF) was used as a test substance to cultivate and to screen microbes active in degrading dioxins. Two microbial species (Pseudomonas aeruginosa and Xanthomonas maltophilia) which could degrade DBF were isolated from the sludge of a Kraft pulp mill wastewater treatment plant. The optimal conditions for biodegrading DBF were 30 and pH 7. Ps. aeruginosa, which had a high growth rate with DBF as carbon source showed high growth rates in the presence of such dioxins as dibenzo-p-dioxin, medium growth with 1-chlorodibenzo-p-dioxin, 2-chlorodibenzo-p-dioxin and 2,8-dichlorodibenzofuran, low growth with 2,6-dichlorodibenzo-p-dioxin and 1,2,3,4-tetrachlorodibenzo-p-dioxin and no growth with octachlorodibenzofuran. These results suggested that the growth rate of Ps. aeruginosa using dioxins as carbon source decreased with the increase in the degree of chlorine substitution. Activity of Ps. aeruginosa biodegrading dioxins was high for DBF, dibenzo-p-dioxin and 1-chlorodibenzo-p-dioxin and low for 2,8-dichlorodibenzofuran, 3,6-dichlorodibenzofuran, 2-chlorodibenzo-p-dioxin and 2,6-dichlorodibenzo-p-dioxin. These results suggested that there is a correlation between growth and the ability to biodegrade dioxins. On the other hand, the efficiency in the biodegradation of 1,2,3,4-tetrachlorodibenzo-p-dioxin was comparatively high although the growth rate on this dioxin was low. Hydroxydibenzofuran, 2-hydroxy-3-allyl-benzofuran and 2-carboxyvinyloxy phenyl acetic acid were identified by gas chromatograph-mass spectrometry (GC/MS) as products of DBF biodegradation by Ps. aeruginosa, suggesting a possible biodegradation pathway for dioxins.

Nitrification, denitrification, and dechlorination in bleached kraft pulp mill wastewater

This study deals with combining the biologi cal removal of organic halogens with the removal of nitrogen from bleached kraft pulp mill wastewater in fluidized-bed reactors under nitrifying and denitrifying conditions. Untreated and biotreated bleached kraft pulp mill wastewaters had no detrimental effect on nitrification or denitrification. The nitrifying biofilm reactor, pregrown on synthetic inorganic feed with ammonia, removed without a lag phase adsorbable organic halogens [7.2 mg Cl (g biomass volatile solids)−1day−1] from bleached kraft pulp mill wastewater and selected chlorophenols from synthetic wastewater. Electron microscopical examination of the biofilm showed that bacteria, morphologically similar to the nitrifying species Nitrosomonas or Nitrobacter, and Nitrosospira were dominant. The denitrifying fluidized-bed reactor, pregrown on nitrate and methanol, denitrified without a lag phase bleached kraft pulp mill wastewater. Under denitrifying conditions, 35% of the total organic carbon content of untreated bleached kraft pulp mill waste water was removed. The reducing power delivered by untreated bleached kraft pulp mill wastewater for denitrification was 2 mmol electrons/mmol carbon mineralized. Dechlorination under denitrifying conditions was negligible.

PACTTM process for treatment of kraft mill effluent

The PACTTM process (powdered activated carbon addition to the activated sludge process) was evaluated for the treatment of Kraft pulp mill wastewater in a series of bench scale experiments. Possibly due to the relatively low strength wastewater, the PACTTM process with carbon doses between 0.5 and 1.0 g/L of influent only performed marginally better than the conventional activated sludge process. Chemical oxygen demand and toxicity, evaluated with the Microtox® assay, were among the parameters monitored. For the operating conditions tested the solids retention time had no impact on performance. The main improvement was increased in adsorbable organic halides (AOX) removal, the magnitude of the improvement was dependent on the wastewater batch and the carbon dose. However conventional activated sludge treatment will meet Ontario's year 2000 AOX regulations. An empirical model from the literature described the data fairly well.

PACT− process for treatment of kraft mill effluent

The PACT− process (powdered activated carbon addition to the activated sludge process) was evaluated for the treatment of Kraft pulp mill wastewater in a series of bench scale experiments. Possibly due to the relatively low strength wastewater, the PACT− process with carbon doses between 0.5 and 1.0 g/L of influent only performed marginally better than the conventional activated sludge process. Chemical oxygen demand and toxicity, evaluated with the Microtox® assay, were among the parameters monitored. For the operating conditions tested the solids retention time had no impact on performance. The main improvement was increased in adsorbable organic halides (AOX) removal, the magnitude of the improvement was dependent on the wastewater batch and the carbon dose. However conventional activated sludge treatment will meet Ontario's year 2000 AOX regulations. An empirical model from the literature described the data fairly well.

Evaluation of dioxin mobility and spoils leaching in a surface coal mine reclaimed with bleached kraft pulp and paper mill biosolids

A surface coal mine in southeastern Ohio has been reclaimed with approximately 15 to 25 cm thickness of biosolids from a bleached kraft pulp and paper mill wastewater treatment plant. Soil, vegetation, rodents, earthworms, insects, fish, frogs, sediment, and algae samples were collected and analyzed for 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran. Water samples from lakes receiving drainage from unreclaimed and biosolids reclaimed areas were collected and analyzed for various parameters, including pH and metals. The trace levels of dioxin and furan in the pulp and paper mill biosolids did not bioaccumulate in rodents, insects, or earthworms or translocate into plants living in the reclaimed area. The trace levels of dioxin and furan in biosolids did not sufficiently migrate to a drainage lake to result in significant concentrations in fish, frogs, algae, or vegetation. The biosolids reclamation resulted in dramatic decreases in spoils leaching of acid, aluminum, calcium, iron, magnesium, manganese, nickel, and zinc. This work supports the thesis that surface mine reclamation with pulp and paper mill biosolids is safe and effective.

紙・パルプ廃水の嫌気性処理 アクアルネッサンス’９０の成果

A study on anaerobic bioreactor using Kraft pulp mill wastewater was performed with UF membrane separation process. The system consisted of pretreatment equipment for oil separation, a stripping system for sulfur compounds, an anaerobic bioreactor for methane fermenation, membrane module equipment for bacterial concentration, and a gas treatment system. The bioreactor had a fixed-bed with an effective volume of 5 m3 packed with pumice stone.In continuous run with the membrane module system, the HRT was 12 hours, maximum BOD loading rate was 35 kg-BOD/m3/day, and maximum BOD removal rate was 93%. Highly efficient continuoud operation was attained with concentration of useful bacteria by the membrane.And, we have also made trial calculation of costs for methane fermentation.

Treatability of Bleached Kraft Pulp and Paper Mill Wastewaters in a New Zealand Aerated Lagoon Treatment System

The effectiveness of the two biological treatment systems operating at a New Zealand bleached kraft softwood integrated pulp and paper mill was assessed. The two systems operate in different configurations. Treatment system A, which receives general mill wastewaters and chlorination stage bleaching discharges utilises deep, aerated lagoons and has a 4.5 day retention time. Treatment system B, which receives alkali extraction bleaching wastewaters and foul condensates, uses a lagoon system with a retention time of 45 days. Detailed chemical analyses of the untreated and treated wastewaters were made. Mass balances were calculated for a range of physical parameters and for specific chlorinated and non-chlorinated organic constituents. Significant differences in the treatability of various constituents were found. In particular, while system A was able to reduce levels of AOX by 65%, no significant reduction in AOX occurred in system B. In contrast, system B reduced levels of chloroacetic acids by 84% while system A did not achieve any statistically significant removal of these compounds. The treatability of chlorophenolic compounds also differed. System A was unable to remove chlorophenols and chloroguaiacols while system B did not reduce levels of chlorocatechols. These results confirm that the treatability of bleached kraft pulp and paper mill wastewater constituents is dependent upon the characteristics of the treatment systems and the compositions of the wastewaters.

A Study of Renovation of Pulp Mill Waste Water

Pulp and paper industry is one of the major water users and discharges large quantities of highly-colored effluent, which causes an environmental pllution problem. The purpose of our study is the renovation and the reuse of its waste water. This paper is concerned with the removal of lignin from kraft pulp mill waste water by means of fly ashes. It was found that fly ashes were nearly as effective as activated carbon in the removal of lignin, and carbon and calcium contained in the fly ashes contributed to that lignin removal. The results of DTA measurements far fly ashes and lignin showed that lignin was decomposed at from 200 to 400°C and the carbon in the fly ashes burns at over 500°C. The spent fly ashes regained fairly their abliity to remove lignin when heated at from 400 to 500°C and added some calcium hydrate. When the total effluent and washing waste water of a KP mill were treated by fly ashes 20g/l, the lignin and COD were removed about 70 and 50% respectively.