Sludge Generation Research Articles

Coagulation and electrocoagulation for co-treatment of stabilized landfill leachate and municipal wastewater

Abstract Landfill leachate and municipal wastewater at various ratios (1:20, 1:10, 1:7 and 1:5) were subjected to coagulation and electrocoagulation (EC). Alum was used in conventional coagulation at pH 6 and aluminum plate as electrode was used in EC at a current density of 386 A/m2 with 5 cm inter electrode spacing. Treatment efficiency was assessed from removal of chemical oxygen demand (COD), total suspended solids (TSS), turbidity, ammonia, nitrate and phosphate. At 1:5 ratio of landfill leachate to municipal wastewater, highest COD removal was with 3.8 g/L alum whereas highest turbidity removal was with 3.3 g/L alum during coagulation. EC exhibited almost similar removal efficiency for all the parameters at different ratios tested except for COD which was considerably higher at 1:20 ratio. Aluminum consumption from electrode was 0.7 g/L following EC as compared to 3.8 g/L alum used in coagulation. The amount of sludge produced was found to be higher with EC as compared to coagulation which could be due to the fact that the electrochemical method was performed for a longer duration than conventional coagulation. For minimal sludge generation, EC reaction time should be ∼30 min. Further studies with EC process on costing and sludge generation will help to advance the technology for wastewater treatment.

REVIEW OF ETHANOL PRODUCTION BASED ON PAPER SLUDGE: PROCESSES AND PROSPECTS

With population growth and increasing industrialization, enormous amounts of agro-industrial wastes are being produced. Without proper use, these keep piling up leading to tremendous pressure on environmental safety. There is also considerable economic interest not only in the proper utilization of these wastes, but also in developing appropriate processes for this purpose. Sludge generated in pulp and paper mills is one of such solid wastes. Although several studies have investigated its reuse, it is still disposed mostly in landfills, leading to environmental pollution. Utilization of this waste could economically benefit for the pulp and paper sector. An innovative and potentially valuable solution seems to be converting it into ethanol, on which a considerable number of reports have published diverse reviews, even though improvements in the technology are still needed. Hence, this study attempts to provide an overview of all studies carried out so far, highlighting key scientific and technological barriers for scaling up and implementing the conversion process. Some suggestions for future research are given, while perspectives and projections point out that adoption of this process could be especially interesting for regions such as Europe and Asia, where the generation of sludge is high and the ethanol production capacity is still low.

Application of a New Method in Identifying the Sludge Deposits from Refineries and Gas Plants: A Case of Laboratory-Based Study

This article reports the application of a new method in identifying the accumulated sludge deposits (e.g., oily sludge, water sludge, and filter sludge). The method is an excellent approach for identifying the inorganic materials found in sludge deposits generated in refineries and gas plants. The phase identification and quantification on inorganic material in the form of corrosion products are important to facilitate chemical cleaning and prevent the reoccurrence to stop the generation of sludges. Therefore, the authors developed a new method to separate the inorganic materials from the hydrocarbon of the as-received sludge samples from the fields. When the sample preparation was taken with great care, the results revealed that this method is fast and can accurately identify very small quantities (>0.5 wt%) of sludge deposits present in the sample. Additionally, if the color of the dichloromethane soluble part collected is changed, it indicates the presence of hydrocarbon in the sludge. Thermal gravimetric analysis results revealed that the sludge contained approximately 3 wt% of inorganic compound, 25 wt% of water, and 72 wt% of hydrocarbon. Subsequently, gas chromatography mass spectrometry analysis results revealed that the type of hydrocarbon was diesel with the C10–C27.

Application of dissolved air flotation process for industrial sludge thickening: A laboratory-scale study

Aims: Increasing population density in cities has led to an increase in industrial and municipal wastewater sludge generation volume. Dissolved air flotation (DAF) can widely be used for water and wastewater treatment. The aim of our study is to evaluate some DAF design parameters on biological sludge thickening which generated from an industrial wastewater treatment plant. Materials and Methods: This experimental research had been carried out as a laboratory-scale study on DAF process to thickening of the biological sludge. The required amount of sludge was taken once from the Amikabir industrial town wastewater treatment plant in Kashan, Iran. After determination of optimal recycling rate, pH, and coagulant dose, effects of pressure (3, 5, and 7 atm), flotation time (5 and 10 min), and coagulant addition were evaluated on DAF process efficiency. Results: According to this investigation results, the optimal pH and dose of coagulant were obtained 7.5 and 200 mg/L, respectively. Maximum process efficiency for the reduction of total dissolved solids (TDSs), total solids (TSs), and turbidity parameters was 61.01%, 84.02%, and 97%, respectively. Furthermore, the results showed that in contrast to time, coagulant addition and pressure have significant effect on DAF process. Conclusion: DAF process had suitable thickening efficiency to removal of TDS, TS, and turbidity on biological activated sludge.

Bioethanol production process rheology

The increase of bioethanol request in Mexico forces to accelerate the construction of new production plants and to implement process improvements. Locally, the main raw material in bioethanol production process is sugar cane molasses. Nevertheless, there are different problems within the process that minimize their production potential. There is a generation of sludge and its embedding at the inner wall of the first distillation column, and its mechanical cleaning causes an attrition and damage on it. This raises greater embeddings and shorter useful life of the column. In order to improve the process efficiency, becomes necessary to study the behavior of raw material and its transformations during the process, through Rheology. Molasses and its transformations are clearly affected by changes in shear rate and temperature. Incrustation, formed in the first distillation column, presented a high consistency index value (K), a strong shear thinning behavior and viscoelastic characteristics. This confirms the high content presence of dextran gum in the incrustation sample. Both results, rheological and physical, concur with the embedding real problems inside the column. Arrhenius model was used to describe the influence of temperature on fermented mash. Activation energy was obtained as well.

Recycled Paper Sludge Microbial Community as a Potential Source of Cellulase and Xylanase Enzymes

Waste disposal from paper and pulp industry is of great environmental concern. Sludge from recycled paper mills favors colonization with different microbial species due to its chemical composition. In this environment, the microbiota can express enzymes that hydrolyze celluloses and hemicelluloses, such as cellulases, β-glucosidases, and xylanases. Understanding microbiota living in such disposal may give directions to what kind of enzymes or bioproducts may be possible to obtain from this microorganism and how to deal with the waste during the process. We have accessed microbial community associated with two steps in the recycled paper sludge generation by high-throughput DNA sequencing: fibrous residue, and wastewater sludge. Bacteroidetes, Proteobacteria and Firmicutes phyla represented more than 96% of the total. From the eukaryote perspective, Vorticella was the most frequent in fibrous residue samples while Acanthamoeba was the most common on wastewater sludge samples. Among the isolates cellulase activity was detectable only from fungi isolates. Half of the bacterial isolates presented xylanase activity, and most of them in high level of activity. Both a metabarcoding and culturing approaches are valuable tools for enzymatic screening in industrial waste disposal.

Review of Sustainability Issues in Non-Traditional Machining Processes

Non-traditional machining processes (such as EDM and ECM) provide alternatives or sometimes the only alternative in generating highly complex 3-D features in very difficult-to -machine materials. This paper reviews recently published work on sustainability issues related to these processes. For example in Electrochemical machining (ECM) the effect of sludge generation and selection of dielectric in Electrodischarge machining (EDM) need to be investigated from the sustainability point of view. All processes need to be studied not only for resulting productivity and accuracy but also their environmental impact during product generation and usage. This paper addresses process mechanisms, surface integrity, sensing and control and sustainabilty issues of EDM, ECM, USM and AFM processes at macro, micro and nano-scales.

Optimization and biokinetic studies on pretreatment of sludge for enhancing biogas production

Excess sludge generation is a major problem in biological effluent treatment processes. Utilization of excess sludge for gas production is an attractive route, which could be enhanced by pretreatment methods. This study involves two sets of experiments. The first set covers mechanical pretreatment of both feed and inoculum. The second set involves alkaline and mechanical treatments of feed and only mechanical treatment of inoculum. Response surface methodology was used for experimental design, analysis and optimization. The optimized mechanical treatment volume of feed was found to be 50%. Diligent mechanical treatment of inoculum resulted in enhanced microbial activity and improved gas production. Reduction in volatile solids, proteins and carbohydrates was observed to a maximum of 63, 84 and 78.5%, respectively. Feed was subjected to alkali treatment in order to reduce mechanical energy input and to improve solubilization. Compared to mechanical treatment alone, enhanced gas production of about 15% was observed at an optimized pH of 11.8 and SRT of 21 days. A biokinetic model was formulated, simulated and validated for the degradation of organics and gas production.

Sludge disintegration model with finite disintegration rate

The activated sludge process is the most widely used biological wastewater treatment method for domestic and industrial wastewaters. One drawback of this process is the production of `sludge'. The expense for treating excess sludge accounts for 50-60% of the operating costs in a wastewater treatment plant. Traditional methods for disposing of excess sludge are increasingly regulated due to environmental concerns about the presence of potentially toxic elements in the sewage sludge. A promising method to reduce excess sludge production is to increase its biodegradability by disintegrating it within the bioreactor. We extend an earlier model by allowing the sludge disintegration reactions to occur at a finite rate. Furthermore, we include a more realistic model for the hydrolysis of particulate matter by allowing the rate of hydrolysis to saturate at high particulate concentrations. We analyze the steady-state operation of an activated sludge system incorporating a sludge disintegration unit to prevent excess sludge production. References A. Alharbi, M. I. Nelson, A. L. Worthy and H. Sidhu. Sludge formation in the activated sludge process with a sludge disintegration unit. In M. Nelson, T. Hamilton, M. Jennings and J. Bunder, Eds, Proceedings of the 11th Biennial Engineering Mathematics and Applications Conference, EMAC-2013, ANZIAM J. , 55:C348–C367, 2013. doi:10.21914/anziamj.v55i0.7803 P. S. Barker and P. L. Dold. Sludge production and oxygen demand in nutrient removal activated sludge systems. Water Sci. Technol. , 34(5–6):43–50, 1996. doi:10.1016/0273-1223(96)00627-0 A. Canales, A. Pareilleux, J. L. Rols, G. Goma and A. Huyard. Decreased sludge production strategy for domestic wastewater treatment. Water Sci. Technol. , 30(8):97–106, 1994. doi:10.1016/S0043-1354(03)00441-X C. P. Chu, W. C. Feng, B.-V. Chang, C. H. Chou, and D. J. Lee. Reduction of microbial density level in wastewater activated sludge via freezing and thawing. Water Res. , 33:3532–3535, 1999. doi:10.1645/0022-3395(2002)088[0718:EOFTEO]2.0.CO;2 E. Egemen, J. Corpening, and N. Nirmalakhandan. Evaluation of an ozonation system for reduced waste sludge generation. Water Sci. Technol. , 44(2–3):445–452, 2001. http://wst.iwaponline.com/content/44/2-3/445 M. Henze, C. P. L. Grady Jr, W. Gujer, G. V. R. Marais, and T. Matsuo. A general model for single-sludge wastewater treatment systems. Water Res. , 21(5):505–515, 1987. doi:10.1016/0043-1354(87)90058-3 M. I. Nelson and E. Balakrishnan. An analysis of an activated sludge process containing a sludge disintegration system. In F. Chan, D. Marinova, and R. S. Anderssen, Eds, 19th International Congress on Modelling and Simulation, MODSIM 2011, 331–337, 2011. http://www.mssanz.org.au/modsim2011/A3/nelson.pdf M. I. Nelson and T. C. L. Yue. A Mathematical Analysis of a Membrane Bioreactor Containing a Sludge Disintegration System . Chem. Eng. Commun. , 201(10):1384–1403, 2014. doi:10.1080/00986445.2013.809001 Y.-K. Oh, K.-R. Lee, K.-B. Ko, and I.-T. Yeom. Effects of chemical sludge disintegration on the performance of wastewater treatment by membrane bioreactor. Water Res. , 41:2665–2671, 2007. doi:10.1016/j.watres.2007.02.028 Z. Wang, L. Wang, B. Z. Wang, Y. F. Jiang, and S. Liu. Bench-scale study on zero excess activated sludge production process coupled with ozonation unit in membrane bioreactor. J. Environ. Sci. Heal. A , 43(11):1325–1332, 2008. doi:10.1080/10934520802177987 Y. Wei, R. T. Van Houten, A. R. Borger, D. H. Eikelboom, and Y. Fan. Minimization of excess sludge production for biological wastewater treatment. Water Res. , 37:4553–4467, 2003. doi:10.1016/S0043-1354(03)00441-X H. Yasui, K. Nakamura, S. Sakuma, M. Iwasaki, and Y. Sakai. A full-scale operation of a novel activated sludge process without excess sludge production. Water Sci. Technol. , 34(3–4):395–404, 1996. doi:10.1016/0273-1223(96)00604-X S.-H. Yoon. Important operational parameters of membrane bioreactor-sludge disintegration (MBR-SD) system for zero excess sludge production. Water Res. , 37:1921–1931, 2003. doi:10.1016/S0043-1354(02)00578-X S.-H. Yoon, H.-S. Kim, and S. Lee. Incorporation of ultrasonic cell disintegration into a membrane bioreactor for zero sludge production. Process Biochem. , 39(12):1923–1929, 2004. doi:10.1016/j.procbio.2003.09.023

Preparation of Fe3O4/TiO2/C Nanocomposites and Their Application in Fenton-Like Catalysis for Dye Decoloration

Fe2+-H2O2 Fenton system is widely applied in water treatment nowadays, but the acidification and sludge generation are crucial problems to be solved. Herein, we report that Fe3O4/TiO2/C nanocomposites (FTCNCs) were able to catalyze the decomposition of H2O2 at neutral pH and can be applied in dye decoloration. FTCNCs were prepared by precipitating TiO2 on Fe3O4 cores via the hydrolysis of tetrabutyl titanate followed by the hydrothermal dehydrogenization of glucose to deposit carbon on Fe3O4/TiO2. The decoloration of methylene blue (MB) in the FTCNC-H2O2 Fenton-like system was monitored to reflect the catalytic activity of FTCNC. The radical generation capability was analyzed by electron spin resonance. Our results indicated that FTCNC-H2O2 Fenton-like system was efficient in decolorizing MB, and the radicals led to the near complete oxidation of MB. The FTCNC-H2O2 Fenton-like system could be used in a wide pH range of 4–9. A greater catalyst amount, a higher H2O2 concentration, and a higher temperature accelerated the decoloration kinetics. FTCNCs showed good activity after the regeneration of 8 cycles. The implication to the practical applications of FTCNCs in water treatment is discussed.

하수처리장별 총인 시설계 슬러지의 인 흡착능 비교

하수처리장별 총인 시설계 슬러지의 인 흡착능 비교

Moringa oleifera-mediated coagulation of textile wastewater and its biodegradation using novel consortium-BBA grown on agricultural waste substratum.

Generation of secondary sludge is a major concern of textile dye removal by coagulation process. Combinatorial coagulation-biodegradation treatment system has been found efficient in degradation of coagulated textile dye sludge. Moringa oleifera seed powder (700mgL-1) was able to coagulate textile dyestuff from real textile wastewater with 98% color removal. Novel consortium-BBA was found to decolorize coagulated dye sludge. Parameters that significantly affect coagulation process were optimized using response surface methodology. The bench-scale stirred tank reactor (50-L capacity) designed with optimized parameters for coagulation process could efficiently remove 98, 89, 78, and 67% of American Dye Manufacturer's Institute (ADMI) in four repetitive cycles, respectively. Solid-state fermentation composting reactor designed to treat coagulated dye sludge showed 96% removal of dye within 10days. Coagulation of dyes from textile wastewater and degradation of coagulated dye sludge were confirmed by Fourier transform infrared spectroscopy (FTIR) analysis. Cell morphology assay, comet assay, and phytotoxicity confirmed the formation of less toxic products after coagulation and degradation mechanism.

Prediction of Methane Generation of Ozone-Treated Sludge from a Wastewater Treatment Plant

ABSTRACTPrior to anaerobic digestion of waste activated sludge (WAS), the pre-treatment of sludge including ozonation is utilized to enhance the rate of methane generation and turn it to feasible bio-resource energy. Biochemical methanogenic potential (BMP) test is a common tool to estimate the biodegradability of raw and ozonated WAS, although, it is a time consuming test requiring expensive gas analysis. The objective of this research is to recognize key parameters essential to predict biodegradability of WAS and create a valid Artificial Neural Networks (ANN) for estimating sludge biodegradability. The results reflect that ANN is an effective estimation tool.

총인 시설계 슬러지를 이용한 혐기성 소화 슬러지에서 재용출된 인의 제거

총인 시설계 슬러지를 이용한 혐기성 소화 슬러지에서 재용출된 인의 제거

Treatment of laundrette wastewater using Starbon and Fenton's reagent

ABSTRACTThe use of grey water for a variety of purposes is gaining increased popularity as a means of preserving scarce freshwater resources. In this work, catalytic oxidation over Fenton's reagent and adsorption techniques using Starbon (mesoporous material derived from polysaccharides) has been applied. These novel techniques are used as an alternative to already studied treatments of grey water such as filtration and/or biological processes. In this study, grey water, collected from a commercial laundrette, has been used. Treatment efficiency was determined by changes in the chemical oxygen demand (COD) of the grey water. Experiments using Fenton's reagent at optimum conditions of Fe3+ = 40 mg L−1; H2O2 = 400 mg L−1 and pH 3 were very successful, resulting in a 95% COD removal after 15 min. Treatment with Starbon adsorption was also effective, reaching up to 81% COD removal at pH 3 within 1 h. The combined treatment with Fenton's reagent and Starbon resulted in a 93% COD removal at a significantly reduced concentration of Fenton's reagent compared to the treatment with solo Fenton's reagent. This lower chemical dose has the advantage of reducing costs and lowering sludge generation.

Oxygen Reduction Reaction on Graphene in an Electro-Fenton System: In Situ Generation of H2 O2 for the Oxidation of Organic Compounds.

Fenton oxidation using an aqueous mixture of Fe(2+) and H2 O2 is a promising environmental remediation strategy. However, the difficulty of storage and shipment of concentrated H2 O2 and the generation of iron sludge limit its broad application. Therefore, highly efficient and cost-effective electrocatalysts are in great need. Herein, a graphene catalyst is proposed for the electro-Fenton process, in which H2 O2 is generated in situ by the two-electron reduction of the dissolved O2 on the cathode and then decomposes to generate (.) OH in acidic solution with Fe(2+) . The π bond of the oxygen is broken whereas the σ bond is generally preserved on the metal-free reduced graphene oxide owing to the high free energy change. Consequently, the oxygen is reduced to H2 O2 through a two-electron pathway. The thermally reduced graphene with a high specific surface area (308.8 m(2) g(-1) ) and a large oxygen content (10.3 at %) exhibits excellent reactivity for the two-electron oxygen reduction reaction to H2 O2 . A highly efficient peroxide yield (64.2 %) and a remarkable decolorization of methylene blue (12 mg L(-1) ) of over 97 % in 160 min are obtained. The degradation of methylene blue with hydroxyl radicals generated in situ is described by a pseudo first-order kinetics model. This provides a proof-of-concept of an environmentally friendly electro-Fenton process using graphene for the oxygen reduction reaction in an acidic solution to generate H2 O2 .

Using of Ferrous Chloride in Anaerobic Digestion of a Substrate with High Sulphur Content

Possibilities of anaerobic processing of substrates rich in sulphur were studied. High concentrations of sulphur cause problems when contained in biogas, as well as inhibition by sulphides in anaerobic processes. The impact of ferrous chloride on anaerobic processes, directly dosed to the anaerobic reactor was studied. This sulphur removal method is commonly known, though the objective of our study was to identify problems when it is applied on substrates rich in sulphur. Waste biomass from cystine production was used as substrate, which is produced in large quantities (17000 t/y) by Biotika, a.s. Slovenská Ľupča and requires processing; sulphur content range from 4 up to 5 % in the biomass. Specific biogas production was 0.410 m3/kg COD i.e. 0.737 m3/kg VSS, while 77 % sulphide inhibition occurred after several dose repetitions. Inhibition decreased to 25.4 % during long-term processing of cystine biomass in a mixed anaerobic reactor. Ferrous chloride dosing, however, resulted in high excess sludge generation, lower organic content in the sludge and high concentration of dissolved inorganic salts. These factors may lead to secondary problems in long-term processing of cystine biomass.

Applicability of plant based biosorbents in the removal of heavy metals: a review

Heavy metals are toxic, persistent, carcinogenic and mutagenic in nature. Industrial wastewater is a widely known source for metal pollution in aquatic bodies as well as surface contamination. There are various techniques available for the removal of heavy metals from wastewater, like ion-exchange, membrane filtration, electrolysis, coagulation, flotation, and adsorption. However, these methods have several disadvantages like high operating cost, sludge generation and selectivity of metals. Among them, adsorption processes are extensively used for heavy metal and other pollutant removal. Biosorption is an eco-friendly, sustainable, rapid and economic process, which increases its wide application. Biosorbents are easily available and low cost in nature. Plant biomasses are commonly used as biosorbents for synthetic and real wastewater treatment. The adsorbent capacity of metal ion removal varies, depending on the nature of the adsorbent, pH, contact time, particle size, and metal concentrations. In this review paper, literature on plant based biomass has been compiled to provide concise information exploring the adsorption efficiencies in removal of toxic metals like cadmium, copper, lead, mercury, cobalt, chromium, arsenic, zinc and nickel. The metal removal efficiencies in batch and column studies are also compared.

Archaeal and bacterial community dynamics and bioprocess performance of a bench-scale two-stage anaerobic digester

Two-stage technologies have been developed for anaerobic digestion of waste-activated sludge. In this study, the archaeal and bacterial community structure dynamics and bioprocess performance of a bench-scale two-stage anaerobic digester treating urban sewage sludge have been studied by the means of high-throughput sequencing techniques and physicochemical parameters such as pH, dried sludge, volatile dried sludge, acid concentration, alkalinity, and biogas generation. The coupled analyses of archaeal and bacterial communities and physicochemical parameters showed a direct relationship between archaeal and bacterial populations and bioprocess performance during start-up and working operation of a two-stage anaerobic digester. Moreover, results demonstrated that archaeal and bacterial community structure was affected by changes in the acid/alkalinity ratio in the bioprocess. Thus, a predominance of the acetoclastic methanogen Methanosaeta was observed in the methanogenic bioreactor at high-value acid/alkaline ratio, while a predominance of Methanomassilicoccaeceae archaea and Methanoculleus genus was observed in the methanogenic bioreactor at low-value acid/alkaline ratio. Biodiversity tag-iTag sequencing studies showed that methanogenic archaea can be also detected in the acidogenic bioreactor, although its biological activity was decreased after 4months of operation as supported by physicochemical analyses. Also, studies of the VFA producers and VFA consumers microbial populations showed as these microbiota were directly affected by the physicochemical parameters generated in the bioreactors. We suggest that the results obtained in our study could be useful for future implementations of two-stage anaerobic digestion processes at both bench- and full-scale.

Agri-food sludge management using different co-composting strategies: study of the added value of the composts obtained

The growth of the agri-food industry has resulted in a strong increase in its sludge generation. This type of waste is often produced in high amounts, concentrated in certain areas, and shows characteristics similar to those of municipal sewage sludge (except for the absence of heavy metals). Composting has been widely studied as a viable alternative for the treatment and recycling of municipal sewage sludge, but little information is currently available concerning the composting of agri-food sludge. Thus, the aim of this work was to increase our knowledge of how the vegetable-derived sludge produced by the agri-food sector can be managed using different co-composting strategies. The work was concerned mainly with the characteristics of the bulking agents used (type and particle size) and their effects on the development of the process and on the potential added value of the composts obtained. For this, four composting piles were prepared using agri-food sludge and two bulking agents (vine shoot prunings and pepper plant pruning waste) at two particle sizes (<1 cm and <3 cm). The evolution of the process and the final properties of the composts obtained were studied using classical analytical methods together with advanced instrumental methods (thermal analysis and excitation–emission matrix (EEM) fluorescence spectroscopy). In addition, their physical characteristics and potential suppression of phytopathogens (Fusarium oxysporum f. sp. melonis) were determined. The results showed differences according to the type and size of bulking agent, the mixtures with vine shoot prunings having a higher biodegradability, which was confirmed by thermogravimetry and EEM fluorescence spectroscopy. Melon plants grown in a mixture which included compost produced using vine pruning waste had a greater shoot weight than those grown on peat alone, while the mixture including compost derived from pepper pruning waste gave a shoot weight similar to that of peat-grown plants. Furthermore, the composts elaborated using vine shoot prunings had added value with respect to their use as growing media components for seedling production of melon, due to their suppression of F. oxysporum f. sp. melonis. Therefore, this study has shown that the nature of the bulking agent used is of major importance not only for the development of the composting process, but also for the final properties and potential added value of the end-products obtained.