Recycling Of Sludge Research Articles

Elucidating biochemical transformations of Fe and S in an innovative Fe(II)-dosed anaerobic wastewater treatment process using spectroscopic and phylogenetic analyses

An innovative process consisting of Fe(II)-dosed anaerobic bioreactors and an oxidizing basin was used to continuously treat a synthetic wastewater (COD/sulfate mass ratio 2:1 and Fe/S molar ratio 1:1). Sludge recycling effects were evaluated on ten occasions, in which anaerobic sludge was collected, biochemically oxidized with mechanical aeration in the oxidizing basin before being mixed with the wastewater influent. The sludge recycling resulted in better effluent quality compared to the baseline operation without recycling. More Fe and S were retained as sludge in the bioreactors with sludge recycling (Fe 94%, S 91%) than those when the bioreactors were operated without sludge recycling (Fe 76%, S 86%). Scanning electron microscopic analysis showed that bacterial cells and iron sulfide intermixed in the anaerobic sludge and the presence of microbial exopolymeric substances. X-ray spectroscopic analyses showed amorphous FeS formed from the dosed ferrous iron and biogenic bisulfide, and suggested long-term conversion of the amorphous FeS to more stable crystalline FeS and FeS2 in the anaerobic bioreactors. In the oxidizing basin, oxidation of iron sulfides was of both chemical and biological nature, and their oxidized forms including amorphous FeO/Fe2O3 mixture and partially/fully oxidized sulfurs. Experimental results also indicated amorphous FeS was more readily oxidized than FeS2. Phylogenetic analysis revealed microorganisms related to Desulfomonile tiedjei (sulfur reducing) and Alkaliphilus metalliredigens (iron reducing) in the anaerobic bioreactors, and Thiobacter subterraneus (sulfur oxidizing) and Rubrivivax gelatinosus (iron oxidizing) related microorganisms in the oxidizing basin.

Reduction of sintering energy by application of calcium fluoride as flux in lightweight aggregate sintering

Thisstudy sinters the mixture of CaF2and dredged reservoir sediment into lightweight aggregate (LWA) at 1000–1100 °C, which is considerably lower than the temperature used by LWA manufacturing industry. The study is aimed to reduce energy demand and carbon emission, and to recycle waste. The sintering temperature is reduced approximately 200 °C by partial replacement of the reservoir sediment with CaF2. Furthermore, LWAs we made have relatively lower water sorption capacity and particle density than the requirement of present construction and civil engineering industries. In addition, F- leaching level from the LWAs is negligible. Using LWA as normal coarse aggregate to make lightweight concrete (LWC) meets the requirement of high-strength concrete. The LWC using our LWA is stronger than the LWCs using commercial LWAs in compressibility strength. Potentially, this study can be applied in the recycling of CaF2-containing sludges, discharged by wafer and liquid crystal display manufacturing plants, as a flux promoter for LWA manufacturing.

Sludge based micro-electrolysis filler for removing tetracycline from solution

In this study, a novel catalytic micro-electrolysis filler (CMEF) was prepared using waste sludge as the main raw materials. The preparation process was optimized in terms of the mass ratio of raw materials and sintering temperature based on the tetracyclines (TCs) removal efficiency. The physicochemical characteristics (e.g., surface area, morphology features, function groups, and valence state of Fe) of the prepared CMEF were determined. Finally, the removing performance and mechanism of CMEF were discussed by removing TCs from solution. The results showed that the optimum conditions for CMEF preparation were a sintering temperature of 1050 °C, and the mass ration for sludge:clay:Fe powder of 3:2:2. The CMEF exhibited a high degradation capacity for TCs with a removal rate up to 99.9% in 2.5 h, and the removal kinetics fit well with a pseudo-second-order model. Introducing Fe into the CMEF significantly promoted TCs removal, comparing to the removal of TCs by sludge based ceramic (without addition of iron). This study provides a novel cost-effective CMEF based on sludge, and is also of significance for co-friend recycling of waste sludge.

Psychrophilic anaerobic dynamic membrane bioreactor for domestic wastewater treatment: Effects of organic loading and sludge recycling

Two upflow anaerobic dynamic membrane bioreactors (AnDMBRs) with and without sludge recycling were operated in parallel at varied organic loadings and psychrophilic temperature for domestic wastewater treatment. A 75 μm nylon mesh, used as a supporting material, enabled quick and stable dynamic membrane formation. The AnDMBRs could operate continuously without relaxation at a high flux rate of 22.5 L/m2h; however, high organic loading accelerated the increasing rate of trans-membrane pressure (TMP). High chemical oxygen demand removal was achieved in both AnDMBRs with removal efficiencies of 70–90%. Sludge recycling enhanced the cross-flow velocity but negatively affected the effluent turbidity, sludge properties (particle size reduction and biopolymer release) and dynamic membrane filterability. Although increased organic loading enhanced biogas yield, the low biogas production was related to the dissolved methane loss in the effluent. Easy-operation, minimal maintenance and low-energy consumption makes the AnDMBR process cost-effective for practical wastewater treatment in temperate areas.

Investigation of Mineral-Processing Wastewater Recycling Processes: A Pilot Study

Mineral processing requires large amounts of water, but, often in the remote locations of many mines, sufficient fresh water frequently cannot be supplied. Therefore, recycling of water is important in mineral processing and enhancing the efficiency of the liquid-solid separation and dewatering steps in mineral processing wastewater treatment is critical. The objectives of the study were to evaluate the effect of anionic flocculant dosage and sludge recycling (SR) on solid removal and sludge dewaterability. Different combinations of the flocculant dosage with and without SR were applied in a mineral-processing wastewater treatment pilot plant. Increasing the amount of flocculant dose of 1.1% v/v (flocculant solution to wastewater) did not significantly decrease the turbidity of the treated water, while the combination of a flocculant with SR increased the zeta potential. Increasing flocculant dose adversely affected dewaterability, although the dewaterability of the 0.6% v/v flocculant-treated sludge significantly increased after aging of the sludge. Sludge recycling was effective for increasing the dewaterability, and a flocculant dose of 1.1% v/v with SR led to formation of large flocs that were stable during aging and sonication.

Controlled experiment contradicts the apparent benefits of the Fenton reaction during anaerobic digestion at a municipal wastewater treatment plant.

A previous study had reported that the Fenton reaction at full scale increased the digestibility of thickened sludge in a digester. The authors of the study had observed a positive effect on biogas productivity, but without a control. Here, we evaluated this result by investigating the anaerobic treatment characteristics of fresh, thickened sludge in an experimental design with a control. To accomplish this, two identical continuously stirred anaerobic digesters (CSADs) were operated in parallel at mesophilic conditions. We also included anaerobic settlers to mimic the full-scale plant and to accomplish sludge recycling. We fed fresh, thickened sludge to both setups once every other day, but performed the Fenton reaction with only the experimental system by adding H2O2 to the recycled biosolids from the anaerobic settler. We observed very large fluctuations in biogas production due to ever-changing characteristics of the thickened sludge both on a daily and seasonal basis. Regardless, the two setups performed almost identically with: 1) chemical oxygen demand removal efficiencies of 63.8 ± 2.9% and 62.1 ± 3.2%; and 2) biogas productivities of 0.280 and 0.279 L CH4·g-1 volatile solids for the experimental (with Fenton) and control (without Fenton) CSADs, respectively. These results indicate that the use of a Fenton reaction did not affect biogas productivities.

Recycling of sludge from drinking water treatment as ceramic material for the manufacture of tiles

Currently, the main destination for sludge from Drinking Water Treatment Plants (DWTP) is its disposal in sanitary landfills. However, its chemical composition and physical properties make it suitable for use as a building material. In this work, the use of spray-dried DWTP sludge on the manufacture of cladding ceramic material for the production of tiles as an alternative to the final disposal of sludge is analysed. The work is based on an experimental study carried out on a laboratory scale. Clay and spray-dried DWTP sludge (average humidity of 3 wt%) were mixed with different percentages of sludge (from 0 to 70 wt%) to form a slurry to be extruded. Specimens were then fired up to 980 °C. Chemical and mineralogical composition of raw materials was analysed. Technical properties of the ceramic samples were determined. The results obtained showed that the DWTP sludge became a powder with low organic content and a high-micronised calcareous content (14.4 wt% calcium oxide). The ceramic samples had a high open porosity, which increases with the increase in sludge addition percentage. They also had a high dilatometric coefficient. Taking into account these two properties, a possible application of this material would be the manufacture of glazed tiles. The resulting ceramic material does not pose any environmental problem, far surpassing the NEN-7345 leaching test and accelerated degassing tests (outgassing PSS-01-702 and offgassing PSS-01-729 standards of the European Space Agency).

Study on Environmental Safety Assessment for Recycling of Inorganic Sludge Generated from the Car Washing Facilities

Study on Environmental Safety Assessment for Recycling of Inorganic Sludge Generated from the Car Washing Facilities

The Evaluation of Hazards to Man and the Environment during the Composting of Sewage Sludge

Composting is considered an effective treatment option to eliminate or substantially reduce potential hazards relating to the recycling of sewage sludge (SS) on land. The variation of four major types of hazards (heavy metals, instability, pathogenic potential and antibiotic resistance) was studied during laboratory-scale composting of two mixtures of sludge and green waste (1:1 and 1:2 v/v). The heavy metal content of the final compost was governed by the initial contamination of SS, with the bulking agent ratio having practically no effect. The composts would meet the heavy metal standards of the United States of America (USA) and the European Union member states, but would fail the most stringent of them. A higher ratio of bulking agent led to a higher stabilisation rate, nitrogen retention and final degree of stability. A good level of sanitisation was achieved for both mixtures, despite the relatively low temperatures attained in the laboratory system. The antibiotic resistance was limited among the E. coli strains examined, but its occurrence was more frequent among the Enterococcus spp. strains. The type of antibiotics against which resistance was mainly detected indicates that this might not be acquired, thus, not posing a serious epidemiological risk through the land application of the SS derived composts.

The properties of water from a concrete plant to be used in cement composites

This article presents the requirements for concrete mixing water and evaluates the possibilities of using recycled waste sludge water generated in a concrete plant from rinsing water of the concrete plant agitating centre and agitation trucks. The production of concrete mix requires large amount of water and for this reason, it is necessary to use this resource in an economic way. For further use of these waters, it is vital to know their detailed properties in order to maximize their potential in the design of concrete formulations for the purpose of replacing pure mixing water with recycled sludge water so as to preserve or improve the physical and mechanical properties of fresh concrete mix or hardened concrete. The results of the wastewater tests from the concrete plant confirm compliance with the limit concentrations according to CSN EN 1008. The attention should be paid to the limit of concentration of sulphates.

Marble Sludge Recycling by Using Geopolymerization Technology

AbstractThe purpose of this study was to investigate the recycling potential of marble sludge, which is generated from the cutting and grinding of marble. Geopolymerization technology was applied t...

Recycling of Waste Sludge: Preparation and Application of Sludge-Based Activated Carbon

With the rapidly increasing industrial and agricultural development, a large amount of sludge has been produced from much water treatment. Sludge treatment has become one of the most important environmental issues. Resource utilization of sludge is one of the important efficient methods for solving this issue. Sludge-based activated carbon (SBAC) materials have high adsorption performance and can effectively remove environmental pollutants including typical organic matter and heavy metals through physical and chemical processes. Therefore, developing efficient SBAC materials is important and valuable. At present, preparation, modification, and application of SBAC materials have gained widespread attention. This paper provides a review of the research on SBAC preparation and modification and its utilization in removing environmental pollutants. It included the following topics present in this review: conventional and new methods for preparation of SBAC were clearly present; the effective methods for improving SBAC performance via physical and chemical modification were reviewed; and the correlation of their physic-chemical properties of SBAC with pollutants’ removal efficiencies as well as the removal mechanisms was revealed. SBAC has a better adsorption performance than commercial activated carbon in some aspects. Furthermore, it is a cost-effective technique and has a wide range of raw materials. However, there are still some drawbacks to its research; thus, some suggestions for further research were given in this review.

Production of biogas from cassava wastewater using a three-stage upflow anaerobic sludge blanket (UASB) reactor

Abstract In this study, a three-stage upflow anaerobic sludge blanket (UASB) system was developed and tested for hydrogen (H2) and methane (CH4) production from cassava wastewater with an emphasis on CH4 production. The experiment was carried out at mesophilic temperature (37 °C) at different chemical oxygen demand (COD) loading rates from 5 to 18 kg/m3d (based on total liquid holding volume) with a recycle ratio of the final effluent to both the first and second bioreactors at a constant 1: 1 flow rate ratio of feed: final effluent. The first bioreactor was maintained pH at 5.5 while those of the other two bioreactors were not controlled. At an optimum COD loading rate of 15 kg/m3d, the system provided the highest COD removal level (92.5%) and the highest H2 and CH4 yields of 0.43 mL H2/g COD applied, and 328 mL CH4/g COD applied, respectively. The very high productivity of CH4 with the very low H2 productivity resulted from the recycled methanogen sludge from the third bioreactor to the first and second bioreactors. The process performance of the three-stage UASB system in terms of optimum COD loading rate and total energy yield was much higher than those of single and two-stage anaerobic processes.

Recycling paper industry effluent sludge for use in mortars: A sustainability perspective

Abstract The paper and cellulose manufacturing industry generates significant quantities of waste, including an extremely humid sludge, which is considered to be an effluent with high environmental liability for the manufacturer. Studies have shown that this waste sludge may be utilized in construction material, such as mortar for fixing blocks, as well as for ceiling and wall coatings that use ceramic masonry as a sealant. The recycling of pulp and paper industry waste sludge has important environmental benefits, by preventing soil and water pollution caused by inadequate disposal and by reducing the depletion of natural resources, such as lime, used in cementitious materials. This study analyzed the sustainability of incorporating such waste into cement-based mortars. Tests were conducted replacing lime, one of the most expensive mortar components with high environmental impact, with waste sludge in contents of 5%, 10%, 15%, and 20%. Analysis was then performed on the samples to assess the primary technical characteristics of these incorporated mortars, such as the consistency index, heat of hydration, content of incorporated air, water retention, mechanical strength and the capillarity coefficient. The results were compared with the results of the characterization tests that were performed on the waste material. The results showed that for use in wall and ceiling mortar coatings, the level of incorporation should not exceed 10%, because higher levels yield lower values of mechanical strength resistance, incompatible with market requirements. This result is probably due to the low heat of hydration of the waste material which generates slower reactions. On the other hand, higher levels of waste material content, above 10%, are appropriate convenient for mortar used to fill small repairs in masonry that do not require control of properties.

Fertilizer Effect of Phosphorus Recycling Products

Between 2004 and 2011 the German Government funded 17 different projects to develop techniques of phosphorus recycling from wastewater, sewage sludges, and sewage sludge ashes. Several procedures had been tested, such as precipitation, adsorption, crystallization, nano-filtration, electro-dialysis, wet oxidation, pyrolysis, ion exchange, or bioleaching. From these techniques, 32 recycling products were tested by five different institutes for their agronomic efficiency, that is, their plant availability, mainly in pot experiments. This manuscript summarizes and compares these results to evaluate the suitability of different technical approaches to recycle P from wastes into applicable fertilizers. In total, 17 products of recycled sewage sludge ashes (SSA), one meat and bone meal ash, one sinter product of meat and bone meal, one cupola furnace slag, nine Ca phosphates from crystallization or from precipitation, Seaborne-Ca-phosphates, Seaborne-Mg-phosphate, and 3 different struvites were tested in comparison to controls with water soluble P, that is, either single super phosphate (SSP) or triple super phosphate (TSP). Sandy and loamy soils (pH: 4.7–6.8; CAL-P: 33–49 ppm) were used. The dominant test plant was maize. Phosphorus uptake from fertilizer was calculated by the P content of fertilized plants minus P content of unfertilized plants. Calculated uptake from all products was set in relation to uptake from water soluble P fertilizers (SSP or TSP) as a reference value (=100%). The following results were found: (1) plants took up less than 25% P in 65% of all SSA (15 products); (2) 6 products (26%) resulted in P uptake of 25 and 50% relatively to water soluble P. Only one Mg-P product resulted in an uptake of 67%. With cupola furnace slag, 24% P uptake was reached on sandy soil and nearly the same value as TSP on loamy soil. The uptake results of Ca phosphates were between 0 and 50%. Mg-P products from precipitation processes consistently showed a better P supply in relation to comparable Ca-P compounds. With struvite the same P uptake as for water soluble P was reached. The fertilizer effect of the tested P recycling products can clearly be differentiated: TSP = struvite > Mg-P = sinter-P > Ca-P, cupola-slag > thermally treated sewage sludge ashes > meat-and-bone meal ash = Fe-P.

Both widespread PEP-CTERM proteins and exopolysaccharides are required for floc formation of Zoogloea resiniphila and other activated sludge bacteria.

Bacterial floc formation plays a central role in the activated sludge (AS) process, which has been widely utilized for sewage and wastewater treatment. The formation of AS flocs has long been known to require exopolysaccharide biosynthesis. This study demonstrates an additional requirement for a PEP-CTERM protein in Zoogloea resiniphila, a dominant AS bacterium harboring a large exopolysaccharide biosynthesis gene cluster. Two members of a wide-spread family of high copy number-per-genome PEP-CTERM genes, transcriptionally regulated by the RpoN sigma factor and accessory PrsK-PrsR two-component system and at least one of these, pepA, must be expressed for Zoogloea to build the floc structures that allow gravitational sludge settling and recycling. Without PrsK or PrsR, Zoogloea cells were planktonic rather than flocculated and secreted exopolysaccharides were released into the growth broth in soluble form. Overexpression of PepA could circumvent the requirement of rpoN, prsK and prsRfor the floc-forming phenotype by fixing the exopolysaccharides to bacterial cells. However, overexpression of PepA, which underwent post-translational modifications, could not rescue the long-rod morphology of the rpoN mutant. Consistently, PEP-CTERM genes and exopolysaccharide biosynthesis gene cluster are present in the genome of the floc-forming Nitrospira comammox and Mitsuaria strain as well as many other AS bacteria.

Recycling of oil sludge together with construction and demolition waste into building materials in Tanzania

The disposal of oil sludge together with construction and demolition waste in Tanzania is still a challenge in both space and technology. In order to reduce the space requirement for oil sludge together with construction and demolition waste disposal, the recycling of these waste becomes a vital option. This paper is mainly concerned with the determination on the possibility of recycling the oil sludge together with construction and demolition waste into building material in Tanzania. The materials used were oil sludge from oil re-refining industry, construction and demolition (CD in future, the metal concentration in the soil is expected to accumulate, which will result into negative impacts in relation to the environment. In the recycling process, different mix ratios of cement, oil sludge and C&D waste were applied. The experiment was meant to determine the optimal mixing ratio. This study demonstrated that the oil re-refined sludge together with construction and demolition waste can be recycled into building material in Tanzania and hence reduce their adverse impacts to the environment. Key words: Recycling, oil sludge, construction and demolition waste, building materials.

Potential Utilization of Sewage Sludge from Water Treatment Plant as Brick Material

One of the results of the water treatment process is the sludge. Generally, the processed sludge from the water treatment is collected and delivered to a landfil. With the delivery of sludge waste, it requires additional cost as a levy in handling sludge waste. Therefore, it is needed to innovate on the recycling of sludge. The waste recycling process is expected to minimize the residual impact of the Water Treatment Plant. The process of waste recycling can be done by utilizing sludge from water treatment, which is brick making process. The benefits can eliminate environmental problems and also some economic problems. This study aims to determine the potential of sludge from water treatment plant to be added for brick making by investigating the physical and characteristics of sludge. The research findings show that sludge waste has the potential to become a brick raw material depending on the nature and clay microstructure

Recycling of alum sludge for alpha Al2O3 production using different chemical treatments

Recycling of alum sludge for alpha Al2O3 production using different chemical treatments

ТЕХНОЛОГИЯ ПЕРЕРАБОТКИ НЕФТЕШЛАМА

This paper compares thermal, chemical, biological and physical approaches to the disposal and recycling of oil sludges. The advantages and disadvantages of these methods are discussed. The conducted comparative analysis has shown that, from the economic and environmental standpoints, the physical approach is best suited for oil sludge recycling at industrial enterprises. A new device - a three-phase decanter - is proposed for the recycling of oil sludge. The decanter is a horizontally-placed centrifuge with a cylinder-conical bowl having a solid outer jacket for a continuous separation of solid particles from suspensions. At the device outlet, oil product samples are shown to contain less than 2% of water and 1% of mechanical impurities, which values conforms to generally accepted standards. The decanter allows oil products to be extracted from oil sludge for subsequent use. It is concluded that the proposed device can be applied by oil production companies to earn additional profit from oil sludge recycling, at the same time as reducing the amount of harmful emissions into the atmosphere.