Sludge Dehydration Research Articles

Effect of combined dialysis method on dewatering of coagulant pretreated sludge

The unique composition and condition of sludge pose significant challenges in water removal. Therefore, it is crucial to investigate a cost-effective and highly efficient approach for dehydrating sludge. In this paper, the domestic sludge was respectively pretreated with ferric chloride, polyaluminum chloride, and cationic polyacrylamide. Then the pretreated sludge was performed on gravity dehydration, centrifugal dehydration, dialysis dehydration and mixed method. The effect mechanism of coagulant and dewatering method on sludge dehydration was analyzed from micro perspective. Finally, the influence range of the dialytic solution was tested by model experiment. The results indicate that the dehydration efficiency of the pretreated sludge with PAC is slightly better than that pretreated with FeCl3 and CPAM, and the optimal dosage of PAC is 8 %. The effect of dialysis dehydration is the best, which can significantly change the final moisture content of sludge (much less than 60 %), effectively achieving the requirements of subsequent processing. The water content of the sludge treated by gravity dehydration, centrifugal dehydration and dialysis dehydration can reach 38 %, which is much smaller than that of the sludge treated by a single dehydration method. The free water, occlusion, coating water, and bounding water are dehydrated by gravity, centrifugal force, and dialysis. The influence range of dialysis dehydration is less than 10 cm. When the distance is more than 10 cm, the difference of sludge moisture content at different relative heights is larger. The study has certain theoretical guidance significance for improving the performance of sludge concentration and dewatering.

Development of the wastewater treatment technology for the mine ‘Ternivska’ of the Kryvyi Rih iron ore plant

ABSTRACT Wastewater treatment in mining and mineral processing technology is a topical problem worldwide. The purpose of this study is to substantiate and develop the technology of complex wastewater treatment for the mine ‘Ternivska’ of the Public Joint Stock Company ‘Kryvyi Rih Iron Ore Plant’ with the production of highly purified water suitable for secondary use or ecologically safe discharge into surface water bodies. The proposed technology is based on the sequential application of the following stages: preliminary treatment of contaminated mine waters by coagulation and soda-lime softening methods to remove hardness, suspended solids, and colloidal substances; desalination via reverse osmosis; evaporation and crystallization of reverse osmosis concentrate in a vacuum evaporation unit; dehydration of salt sludge in a centrifuge with drying of salt crystals in a dryer. The treatment of mine water with an initial salinity of 80 g/L will give an annual effect of 1357 thousand m3 of desalinated water with a mineralization of up to 100 mg/L and 739.6 tons of mineral salt mixture. The purified water can serve as an additional source of fresh water for technological needs in industry or alternative purposes. The obtained solid salt product can be used as an alternative reagent for water-softening processes. In general, the proposed processing of mineralized mine water can be considered a zero-waste technology with clean water production and by-product utilization.

Комплексные решения по управлению хвостовым хозяйством на Усольском калийном комбинате

Introduction. At enterprises engaged in the extraction and processing of mineral raw materials, the volume of production waste is usually much higher than the volume of a commercial product. At the same time, there is a tendency to decrease the metal content in ores while increasing the volume of waste rock extracted when accessing ores. According to various estimates, the annual volume of waste from mining enterprises is 7 billion tons per year. The proportion of waste (tailings) in some copper-containing ores can reach 98 % or higher. Gold mining enterprises process ores in which tailings amount to 99.9 % and which contain only a few grams of gold. This trend will continue, as the enterprises of the mineral processing industry have to increase the volume of processed products. Materials and methods. Tailings processing technology solutions include equipment and services that can be used in almost any tailings farm, while tailings thickening and paste thickening can be used. Just as in the case of surface tailings management solutions, the development of solutions for underground workings begins with consideration of the available storage space underground. Post and dry storage technologies combined with closed water circuits represent the best options available for saving water in processing plants. In traditional tailings systems, the source of process water is natural sources or groundwater from mine drainage. Results. The use of sludge dewatering technology has significant advantages in handling excess brines, because it allows you to separate the mother liquor, return it to the technology and thereby prevent discharge to the sludge storage. To enhance the effect of sludge dewatering, it is necessary to limit the supply of fresh water to the technological process beyond the level of irretrievable losses (for example, evaporation into the atmosphere) by using a mother liquor or recycled brine instead of water. Discussion. liquid phase entering the sludge storage, increase the efficiency of hydraulic transport, and increase the service life of tailings facilities. Scientific works confirm the possibility of using filtered sludge from potash factories as a meliorant for agriculture and restoration of forest soils after fires. When implementing integrated tailings management, it is necessary to take into account the existing conditions and limitations of the site, the requirements of the technological process of a particular enterprise. Conclusion. The article presents the results of research on the dehydration of sludge of potassium salts. It has been established that the sludge dewatering technology significantly reduces the volume of sludge entering the sludge storage, which will increase the efficiency of hydraulic transport, increase the service life of tailings facilities. Resume. The use of sludge dewatering technology can significantly improve the efficiency of the processing plant. The development of sludge dewatering technology will require a number of research projects on transportation, storage and logistics of meliorant.

Theoretical aspects of sludge treatment schemes

Сonsiders the stages of the life cycle of waste water from sedimentation tanks and facilities for processing wash water from fast filters: formation, compaction, dehydration and disposal. A processing model has been formed and the influencing factors on the concentration of suspended solids in each of the stages have been established. Based on the theories of sediment movement, the theory of sediment compaction prof. E.F. Kurgaev and the theory of drying acad. A.V. Lykov proposed a mathematical description of the sludge treatment scheme. The obtained results are confirmed by the choice of influencing factors on the rate of sludge dehydration and confirmed by empirically obtained results.

ОБЕЗВОЖИВАНИЕ НЕФТЕШЛАМОВ ОЧИСТНЫХ СООРУЖЕНИЙ С ПОСЛЕДУЮЩИМ ВОВЛЕЧЕНИЕМ В СТРОИТЕЛЬНЫЕ МАТЕРИАЛЫ

The physicochemical characteristics of oil sludge generated during the purification of industrial wastewater from oil refineries have been studied. Options for dehydration of oil sludge with sub-sequent inclusion in construction materials have been studied

Effects of ceramsite derived from sewage sludge combined with the O3-FeCl3/PAM process on the dewatering of waste-activated sludge and investigation of dewatering mechanisms.

The high water content of waste-activated sludge restricts the subsequent disposal of sludge. The dehydration properties of O3, ferric chloride (FeCl3)/polyacrylamide, and sludge ceramsite sand (SCS) were studied. Simultaneously, the effect of combining the three was investigated to support the deep dehydration of waste-activated sludge. Experimental results showed that with13.42 mg/(g dry solids (DS)) of O3, 109.89 mg/(g DS) of FeCl3, and 100 mesh dosage of 70% DS of sludge ceramsite on weight, the highest sludge net yield was 7.13 kg/(m2·h) and the minimum specific resistance to filtration of sludge cake was 1.02 × 1012 (m/kg). Compared with the compressibility of the raw sludge, the compressibility of the sludge cake decreased by 37.48%. Moreover, the YN (net yield) increased by 73.55%. The results demonstrate that the structure of cracking, flocculation, and hydrophobic framework is the mechanism of sludge dewatering in this combined process. This combined treatment process provides a new perspective for the realization of deep dewatering of sludge and is anticipated to be a successful sludge dehydration method.

Effect of pH value on effectiveness of biopolymer-based treatment of bauxite mine slurry

Effective dehydration and flocculation of mine slurries or sludge is important for nonferrous metal industries and environmental engineering. However, the mechanisms for the flocculation of slurry remain largely unclear. This paper presents the results of a series of flocculation tests, which was conducted on the slurry suspensions treated by xanthan gum (flocculant) at different pH values. It is shown that the settlement rate of mine slurry particles can be accelerated by adding xanthan gum, and the maximum sedimentation rate was obtained at a pH value of 5.9, and the final volume of flocs is significantly increased due to the addition of the flocculant. In addition, the settlement rates of xanthan gum-treated slurry suspensions at the pH values of 3, 5 and 7 decrease slightly compared with the reference slurry suspensions with pH=5.9, and the slurries remained stable as suspensions at the pH value of 9 and 11. The zeta potential measurement and SEM image analysis show that flocculation occurs primarily due to electrostatic attraction between slurry particles and the flocculants, and the bridging effect between the carboxylic groups in the side chains of xanthan gum molecule and the suspension particles.

All-in-one strategy to prepare molded biochar with magnetism from sewage sludge for high-efficiency removal of Cd(Ⅱ)

Biochar in powder could lead to the separation difficulties after using and easy dispersion by wind with non-necessary consumption during the practical application. The current method for preparing molded biochar is multi-step, tedious, and required exogenous reagents. Moreover, the dehydration of sewage sludge with high water content (>85%) causes expensive production cost, limiting its secondary utilization. Therefore, an “all-in-one” strategy was developed to prepare molded biochar with magnetism by using sewage sludge as endogenetic binder, water source, carbon source, as well as magnetic source, and biomass wastes as water moderator and pore-forming agent. The molded biochar showed high removal capacity towards Cd(Ⅱ) of 456.2 mg/g, which was 6 times higher than the commercial activated carbon in powder (69.1 mg/g). The excellent removal performance of the molded biochar was in linear correlation the O/C ratio (R2 =0.855), resulting in the complexation with Cd(Ⅱ). DFT calculations indicated the amounts and species of oxygen changed the electron distribution and electron-donation properties of biochar for Cd(Ⅱ). Moreover, the Na+ exchanges with Cd(Ⅱ) were also an important removal mechanism. This study provided a novel synthesis strategy for the molded biochar with both high particle density and high adsorption capability.

Effect of carbon to nitrogen ratios of municipal sludge on its dehydration property

ABSTRACT Municipal sludge is the main by-product in the process of sewage treatment, and the primary problem to be solved for its harmless disposal or energy utilization is its poor dehydration property. In this paper, biological conditioning technology was used to ferment municipal sludge with methanogens under different carbon to nitrogen ratios (C/N) through an anaerobic fermentation system. The mechanism of improving sludge dewatering performance under fermentation and the effect of C/N of sludge on its dehydration property were investigated. The results showed that the flocculent structure of the sludge was destroyed by the fermentation of methanogens, the sludge’s inherent moisture was released, and the dehydration property was promoted. With the change of C/N from 8 to 20, the hydrophilic oxygen-containing functional group content of the sludge decreased first and then increased. When C/N was 16, the content of hydrophilic oxygen-containing functional groups diminished to the lowest level. Meanwhile, the surface of the sludge showed dense microscopic cavities and small holes, indicating that the sludge flocs had been cracked to a large extent, and thus the ability of the sludge to bind water was weakened. The bound water content of the fermented sludge from low to high was 48.9, 59.0, 64.3, and 71.7% respectively, with C/N of 16, 12, 20, and 8. Therefore, within the scope of this experiment, the optimal C/N for the sludge dehydration property could be identified as around 16, which could reduce the bound water content of the sludge from 87% to 48.9%.

In situ generation of H2O2 for Fenton oxidation in electrochemical system for the enhancement of sludge dehydration

Fenton methods can effectively improve the dewatering performance of waste activated sludge (WAS). However, the explosive properties of H2O2 and demand of real-time dosing often incur transportation difficulties and high operational costs. It limits large-scale applications of Fenton processes on WAS dewatering. This study introduced the electro-Fenton technique by in-situ H2O2 generation into sludge dewatering for the first time. The responding surface methodology indicated that the yield of H2O2 could reach 10.11 mg/g DS (dry solids) at an optimal iron dose of 8 mg/g DS within 60 min. Compared to WAS, the capillary suction time (CST) and specific resistance to filtration (SRF) of treated sludge decreased from 87.7 ± 0.57 s and 3.67 × 1012 m/kg to 57.65 ± 0.92 s and 3.14 × 1012 m/kg, respectively. The mechanism investigations showed that electro-Fenton treatment reduced surface negative charge of WAS and caused disruption of extracellular polymeric substances and release of intracellular substances, which enhanced the flocculability and filtering performance, but decreased the moisture content, fractal dimension of WAS. Additionally, electro-Fenton treatment altered the secondary structure of proteins, which led to a loose structure of protein, benefiting the exposure of hydrophobic sites or groups in EPS proteins. Furthermore, the dewatering mechanisms involved in the electro-Fenton process were explored and the contribution of individual reactions in sludge dewatering was revealed. Overall, this work will provide both theoretical basis and practical knowledge for electro-Fenton sludge dewatering.

Production of Drinking Water with Membranes with Simultaneous Utilization of Concentrate and Reject Effluent after Sludge Dewatering.

A new technology is described that enables us to completely exclude liquid discharges during production of drinking water from surface sources. The proposed described technological scheme separates the natural water into a stream of purified drinking water and dewatered sludge. The sludge moisture has a value of 80 percent. The experimental program is described to treat the natural water with nanofiltration membranes and to produce a drinking-quality water with recovery value of 0.99 and higher. Concentrate of membrane plant is mixed with the wet sludge and the reject effluent after sludge dewatering is again treated by reverse osmosis membranes and returned back to the sludge thickening tank. Results of experiments to treat reject water after sludge dewatering are presented. The use of nanofiltration membranes provides reduction in the Total Dissolved Solids content (TDS), aluminum, color and oxidation to meet drinking water standards. Experimental plots are presented that can be used to select membrane characteristics and to predict product water chemical composition at each stage of the membrane treatment scheme. Concentrate of membrane treatment plant is mixed with the wet sludge in the thickening tank. The sludge, after the thickening tank, is dewatered using either filter-press or centrifugal equipment. The reject (or fugate), after sludge dewatering, is treated by membrane facility to separate it into deionized water stream and concentrate stream. The deionized water can be mixed with the feed water or drinking water and the concentrate stream is returned back to the thickening tank. Thus, the salt balance is maintained in the thickening tank, whereby all dissolved salts and impurities that are rejected by membranes are collected in the thickening tank, and then are withdrawn together with the dewatered sludge. Based on the results of experimental data processing, balance diagrams of the sludge dehydration process with waste water purification at the membrane plant and with the addition of the membrane plant concentrate to the sludge thickener are presented, according to which all contaminants removed by the membranes are removed together with the sludge.

Sludge-based baking-free brick prepared by sewage sludge with high moisture content: Influence of process parameters and environmental risk assessment

The high-water content and difficult dehydration of sewage sludge are the main factors restricting its disposal and application in China. In the paper, the sludge-based baking-free brick (SBFB) was made from sludge and fly ash - carbide slag - desulfurization gypsum with a certain amount of aggregate using compaction forming technology. The influence of process parameters (e.g., sludge content, aggregate content, molding pressure, curing method and curing temperature) on the properties of SBFB were investigated. Additionally, the environmental risk assessment of heavy metals and organic pollution of SBFB samples were carried out. The results indicated that when the sludge content was less than 30 %, the SBFB strength reaches 13.7 MPa under wet-heat cycle curing, which can meet the national standard of nonbearing wall for building bricks. According to the analysis of SEM and XRD, mullite and silicalite crystals were needle-like structures, which made the sludge particles closely linked with solid waste and compact structure. The appearance of these crystal structures was the internal driving force for the later strength of SBFB. Values of risk assessment criteria decreased through solidification treatment, in which Cd decreased to no risk, As, Pb, Zn decreased to low risk, Cu, Ni had moderate risk. All heavy metals were within China standards (GB5085.3–2007). Compared with sludge, the degradability of protein under curing conditions was greater than 77.35 % because of the decomposition of proteins in gel reaction system.

Application of Advanced Oxidation Technology in Sludge Conditioning and Dewatering: A Critical Review.

Sludge dewatering is an important link in sludge treatment. In practical engineering, the dewatering effect of unconditioned sludge is very poor. The use of advanced oxidation technology can improve sludge dewatering performance, reduce sludge capacity, and remove micro-pollutants, which is beneficial for sludge post-treatment and disposal. Based on the current status of sludge conditioning and dehydration, the characteristics of the advanced oxidation method for sludge dehydration were systematically explained using various free radical reaction mechanisms and dehydration conditions. The effects of various advanced oxidation technologies on sludge conditioning and dewatering has been extensively discussed. Finally, the application prospects of the advanced oxidation technology in sludge conditioning and dewatering are presented.

Influence of Different Types of Dewatering Agents on the Solidification Effect and Physical and Chemical Properties of Sediment

In order to study the comprehensive effects of different types of dehydrating agents on the dewatering and solidification of dredged sediments, this study took the dredged sediments of Taihu Lake as the research object and selected microorganisms, polymeric iron aluminum salts, organic polymers, organic-inorganic composites, and aluminum salt microorganisms. These five types of composite dehydrating agents were used to conduct a three-month solidification test on the dredged sediment by means of geotechnical pipe bag solidification. The results of the study showed that the dehydration efficiency of organic polymers and organic-inorganic composite chemicals was better. After one month, the water content of sediment dropped to 61.78% and 63.26%, respectively, which then dropped to 40.56% and 32.16% after three months. Compared with that of the unsolidified sludge, the total nitrogen of the bottom sludge after solidification by the organic-inorganic composite agent was reduced by 74.82%, reaching 591 mg·kg-1, primarily due to the reduction in ammonia nitrogen. The solid sludge contained mainly aluminum-bound phosphorus, calcium-bound phosphorus, and iron-bound phosphorus. Among them, four groups (organic-inorganic composite) had the largest reduction in active phosphorus, with the lowest being 64.3 mg·kg-1. In addition, organic polymer agents had the best curing effect on heavy metals, the comprehensive ecological risk index of heavy metals was reduced by 51.3%, and the leaching toxicity concentration was far below the standard threshold. This study showed that organic polymers and organic-inorganic composite medicaments have a better effect on the dehydration and solidification of bottom sludge and thus have good application prospects.

Effects of potassium ferrate-walnut shell pretreatment on dehydration performance of residual sludge.

Sludge dehydration is not only the first process of sludge reduction but also difficult for sludge treatment and disposal, while the high moisture content of sludge would also limit its resource utilization. In this paper, the residual sludge was treated by the strong oxidizing property of potassium ferrate (PF), and walnut shells were used as a skeleton builder to obtain the recycling dehydrated sludge. It also provides a new solution for the poor stability of PF in the treatment of sludge and waste walnut shells. The experiment results showed that the optimum dosage of PF and walnut shell was 60mg/gDS and 0.8g/gDS, respectively, and the water content of the combined PF and walnut shell treatment decreased by 5.2% and 3.7% compared to that of PF conditioning alone and walnut shell conditioning alone, respectively. In addition, scanning electron microscopy and three-dimensional fluorescence spectroscopy revealed a large number of cracks on the sludge surface after the combined treatment, and the sludge floc structure became more loose and dispersed, and the hydrophobic substances humic acid and fulvic acid increased, indicating that the dewatering performance of the sludge was effectively improved, further confirming that the combined PF and walnut shells treatment provides a new idea and method for sludge dewatering.

Enhanced Dewatering of Activated Sludge by Skeleton-Assisted Flocculation Process.

Sludge dewatering is the fundamental process of sludge treatment. Environmentally friendly and efficient sludge conditioning methods are the premises of sludge to achieve dehydration reduction and resource utilization. In response to sewage plant sludge dehydration, fly ash (FA), polymerized aluminum chloride (PAC), and polymer sulfate (PFS) were studied separately to determine their sludge dehydration performance, and the effects of these three conditioner composite regulations on sludge dehydration properties were studied. Compared to the sludge treated only with conditioner, the average particle size of floc increased and the organic matter content in the filtrate decreased. The sludge dewatering efficiency after the conditioning effect is better than that after conditioning a single conditioner. After PFS conditioning with fly ash, the water content and specific resistance (SRF) of the sludge cake can be reduced to 76.39% and 6.63 × 1010 m/kg, respectively. The moisture content and specific resistance (SRF) of the sludge cake can be reduced to 76.10% and 6.91 × 1010 m/kg, respectively. The pH of the sludge and filtrate changed slightly after PAC conditioning with fly ash coupling. These results indicate that fly-ash coupled with PAC and fly-ash coupled with PFS are expected to become a novel and effective environmental protection combined conditioning method for sludge dewatering.

New biopolymer from biomass for conditioning and dehydration of sewage sludge: application on the sludge of Bouira WWTP.

Sewage treatment plants in Algeria produce huge quantities of sludge expressed in tons annually. This sludge produced is unfortunately contaminated because of the use of synthetic polyelectrolytes. Recently several kinds of research have been carried out on natural flocculants for sludge conditioning, because of several advantages they present such as their renewable source and their non-toxicity. This work aims to evaluate the potential use of protonated pectin extracted from orange waste of N'GAOUS juice factory as an eco-friendly flocculant in the chemical conditioning of sludge. Protonated pectin effectiveness was compared with synthetic cationic anionic and ionic polyelectrolytes (SUPERFLOC 8396, AF400, NF102). In this context, raw sludge samples from Bouira WWTP were tested. Specific resistance to filtration (SRF), cakes dry solid content were analyzed to determine filterability, dewatering capacity of conditioned sludge, and the optimum dose of each conditioner. So that our goal was to obtain greater dryness, which is the case with the addition of protonated pectin and even the addition of Superfloc, which allowed us to obtain dryness of 33.01% and 29.19%, respectively, for the same doses that gave the lowest SRF. Based on the results found and the analysis of the specific resistance to filtration (SRF) and the dryness, and compared with the values observed for the dewatered sludge by the method used in the Bouira WWTP. Band filters (18-22%) and raw sludge (4.8-5.7%).

Batch and semi–continuous experiments examining the sludge mesophilic anaerobic digestive performance with different varieties of rice straw

Anaerobic co–digestion of excess sludge (ES) and different varieties of rice straw including indica rice straw (IRS), japonica rice straw (JRS) and glutinous rice straw (GRS) was investigated in batch and semi–continuous experiments. The batch experiment results showed that the GRS addition presents the highest hydrolysis and methanogenesis rates, its cumulative methane yield (CMY) was 305.75 mL/g VS and its average methane content was 60.56%. After digestion, the structure of GRS was almost completely destroyed, which was beneficial to the degradation of lignocellulose. The digestive process is affected by the abundance of Actinobactereria, Proteobacteria, Methanosaetae and Methanosarcina. The results of semi–continuous digestion were similar to batch digestion. In addition, the addition of GRS increased TN concentration in biogas residue and TP concentration in biogas slurry, but was not conducive to the subsequent dehydration of sludge.

Energy Efficient Steam Atmospheric Dryer with Thermocompressor for Wastewater Sludge Dehydration

Energy Efficient Steam Atmospheric Dryer with Thermocompressor for Wastewater Sludge Dehydration

Novel semi-decentralised mobile system for the sanitization and dehydration of septic sludge: a pilot-scale evaluation in the Jordan Valley

The provision of effective sanitation strategies has a significant impact on public health. However, the treatment of septic sludge still presents some challenges worldwide. Consequently, innovative technologies capable of an effective and efficient sludge treatment, mostly at a decentralized level, are in high demand to improve sanitation provision. To address this problem, this study evaluates a novel semi-decentralised mobile faecal sludge treatment system, the pilot-system for which consists of a combination of several individual processes including mechanical dewatering (MD), microwave (MW) drying, and membrane filtration (ultrafiltration [UF] and reverse osmosis [RO]). The system evaluation was carried out by treating raw, partially digested faecal sludge (FS) from septic tanks—hence, septic sludge (SS)—in the Jordan Valley, Jordan. The pilot-scale system exhibited an effective and flexible treatment performance for (i) sanitizing faecal sludge and related liquid streams (MW and UF); (ii) reducing the treated sludge mass (and sludge volume) (MD and MW); and (iii) producing a high-quality treated liquid stream ideal for water reclamation applications (UF and RO). The MD process removed approximately 99% of the initial SS water content. The MW drying system completely removed E. coli and dehydrated the dewatered sludge at low energy expenditures of 0.75 MJ kg−1 and 5.5 MJ kg−1, respectively. Such energy expenditures can be further reduced by approximately 40% by recovering energy in the condensate and burning the dried sludge, which can then be reused inland applications. The membrane filtration system (UF and RO) was able to produce high-quality treated water that is ideal for the water reuse applications that irrigation requires, as well as meeting the Jordanian standard 893/2006. In addition, the system can also be powered by renewable energy sources, such as photovoltaic energy. Therefore, this research demonstrates that the evaluated semi-decentralised mobile system is technically feasible for the in situ treatment of SS (sanitization and dehydration), while also being effective for simultaneously recovering valuable resources, such as energy, water, and nutrients.