1,720,983 research outputs found
Water recovery from floor cleaning operations of industrial or public areas: The results of a field test
Full text linkWater resources are increasingly under pressure because of human activities and economic development. Moreover, accelerated urbanization and the expansion of drinking water supply and sanitation systems contribute to this rising demand. The development of water reuse solutions is an urgent issue. This study presents a solution for the reuse of wastewaters generated from floor cleaning operations of industrial or public areas. A portable device containing a grid, for coarse filtration, and a 300-L reaction chamber to carry out the sequential processes of coagulation, flocculation and settling, was employed for a field test. In the field test the wastewater coming from the tank of a cleaning machine, used for floor cleaning in an industrial site, was treated and reused for the same purpose for a total of 110 times. The quality of the treated wastewater was monitored cycle after cycle and the results of the test demonstrated that the treated water was suitable to be reused for the same purpose, even after a large number of cycles, provided that a finishing treatment was eventually supplemented in order to reduce the residual concentration of organic substances. It was demonstrated that, under standard operating conditions, that is a wastewater with a total suspended solid (TSS) content of 800 mg/L, and on the grounds of the results found in the test, that is a TSS removal efficiency of 98% and a sludge total solid (TS) content of 6%, the whole volume of the cleaning machine tank was completely renewed with fresh water after 60 cycles. Eventually, the combination of treatment and reuse operations allowed to save approximately 18,000 L of fresh water over a series of 60 cleaning cycles. The proposed treatment allowed not only to save fresh water but even to reduce the cost of water usage by approximately 50%. In fact, thanks to this treatment, the cost of a single cubic meter of water decreased from approximately 6 €/m3, which included supply of fresh water and discharge to the public sewer, to approximately 3 €/m3
A Circular Approach for Recovery and Recycling of Automobile Shredder Residues (ASRs): Material and Thermal Valorization
No full textAbstract: The transition of the automotive industry towards a circular economy requires viable solutions for end-of-life vehicle (ELV) reuse, recycling and recovery. This study tested the feasibility of two recycling processes intended, the first, to produce recycled plastic composite goods from selected plastic fractions extracted from ASRs, through a conventional mechanical process; the second, to use the remaining ASRs as a solid recovered fuel (SRF) to saturate the residual treatment capacity of the local (Turin, NW Italy) municipal solid waste (MSW) incineration plant. Samples of light (CER code 191004) and heavy (CER code 191204) ASRs were collected from an ELV authorized treatment facility, subjected to a complete characterization and tested for the two recycling options. The results demonstrated that selected fractions of thermoplastic polymers could be employed in a molding process for the production of recycled plastic composite goods. This fraction, equal to 2660 t/a, was more than 2% b.w. of the original ELV and 7.6% of the whole ASR waste product. The remaining ASR, after plastic extraction and recycling, had lower heating values (LHVs, 24 or 31 MJ/kg, depending on the original product) and chlorine content (< 50 mg/kg) that made it suitable to assume the status of SRF. In the present operating conditions, the Turin MSW incineration plant has a residual treatment capacity of at least 45,000 t/y, for waste with a LHV of 30 MJ/kg, that is approximately 30% more than the annual amount of ASRs produced in the Turin area. The application of mass and energy balances to the thermal process demonstrated that the addition of ASRs as an extra fuel to the incineration plant did not worse the quality of flue gases in terms of acid compound (HCl, SO2) concentration and allowed the annual net electrical energy production to be increased from 31 to 38 MW. Graphic Abstract: [Figure not available: see fulltext.
Use of spectroscopic indicators for the monitoring of bromate generation in ozonated wastewater containing variable concentrations of bromide
Full text linkTime-resolved monitoring of bromate and other by-products formed into effluents treated with ozone or advanced oxidation processes in wastewater treatment plants (WWTPs) is time-consuming and expensive. This study examined whether concentrations of bromate formed in wastewater after ozonation in the presence of widely varying bromide levels (from ca. 0.7–21.2 mg/L) can be quantified based on measurements of changes in optical properties (differential UV absorbance (ΔUVA), spectral slopes, total or regional fluorescence) of the ozonated samples. Batch ozonation was carried out using a secondary effluent produced at a major wastewater treatment plant located in the Metropolitan Seattle Area. The tests involved raw and bromide-spiked samples treated with ozone doses from 0.1 to 1 mg O3/mg DOC. Measurements of the absorbance at 254 nm (UVA254), fluorescence and bromate concentrations were performed on the treated samples. In the ozonated wastewater the concentration of bromate increased approximately linearly, from 10 mg/L) tended to inhibit the generation of bromate. Relative reduction of UVA254 and total fluorescence (TF) were found to be good predictors of bromate generation. Specifically, exponential curves could adequately fit the non-linear relationships found to exist between the concentrations of bromate and the relative reductions of the UV254 and TF, for any initial bromide concentrations used in this study. Little formation of bromate was found to occur for reduction ranges for UVA254 and TF of 30–40% and 70–80% respectively. Conversely, rapid increases in bromate generation were observed when the decrease of UVA254 or TF exceeded these threshold values
Orthophosphate vs. bicarbonate used as a buffering substance for optimizing the bromide-enhanced ozonation process for ammonia nitrogen removal
No full textBromide-enhanced ozonation (BEO) process can be a fast and effective solution for the complete removal of total nitrogen (TN) from wastewaters containing from moderate to high concentrations of ammonia nitrogen (AN). Like the traditional biological process of AN oxidation, even BEO requires the presence of buffering agents, in order to oppose the progressive acidification induced by the reaction. This study compares the effect of two buffering substances (namely bicarbonate and mixtures of orthophosphates) in hindering the acidification caused by AN oxidation and, consequently, optimizing the overall efficiency of the process. Tests were carried out with on-purpose made solutions containing concentrations of AN of 5–10 mM. The range of [Br−]/[O3] ratio values was from 12 to 18, so as to make ozone the limiting factor in HOBr generation. The results of this study proved that, in the absence of natural buffering agents, mixtures of orthophosphates must be preferred to the more traditionally employed bicarbonate to control the pH evolution of BEO process. In fact, orthophosphates proved to be capable to guarantee an initial pH of the wastewater in the order of 7.5, thus making the zero-order AN removal rates 15% faster than those observed in the presence of bicarbonate. Furthermore, in the presence of mixtures of orthophosphates, the generation of ozonation byproducts in the oxidized form (nitrate, bromate) was reduced by over 70%. Finally, the fine control of pH obtained with orthophosphates in the BEO of AN makes that process an attractive solution for the treatment of effluents containing AN, thus preventing the discharge of residual nitrogen into aquatic environments and avoiding eutrophication of receiving water bodies
Membrane aerated biological reactors (MABRs) to enhance the biological treatment process at a WWTP
Full text linkThe goal of climate neutrality, under the provision of the European Green Deal, will require great efforts to wastewater treatment plants (WWTPs) to reduce and optimize their energy consumption. The utilization of membrane aerated biological reactors (MABRs) to renovate existing WWTPs could be an opportunity in this sense. In this study, the control of the flow at the outlet of a pure, open-end MABR was used as a strategy to minimize the oxygen consumption and obtain high oxygen transfer efficiencies (OTEs). OTE values of more than 80% were observed, which are not so common in the literature and are comparable to those obtained with a close-end configuration. High efficiencies (85%) were found for the removal of both COD and total nitrogen from samples of real wastewater. A techno-economic analysis, comparing a conventional activate sludge (CAS) plant with a MABR, both with a treatment capacity of 25,000 equivalent inhabitants (e.i.), found that the MABR only needed approx. 1/5 of the energy required by the CAS. A MABR plant could become a profitable investment, under a fixed return time of 5 years, compared to a CAS with a CAPEX of 123.7 k€, if the overall cost of the cassettes was inferior to 237 k€. A sensitivity analysis imposing a variation of ±50% on the input parameters (cost of blower, diffusers, electric energy, and opportunity cost of capital) demonstrated that the cost of electric energy had the highest impact on the maximum allowable value of the MABR investment, which was affected by ± 26% with respect to the value calculated in the reference scenario
Feasibility of biogas upgrading at a WWTP after pre-treatment application: Techno-economic assessment validation with pilot test data
Full text linkImproving the efficiency of anaerobic digestion (AD) of sewage sludge (SS) is a critical step toward the achievement of energy neutrality in wastewater treatment plants (WWTPs), as required by the European Green Deal. This study used a comparative techno-economic assessment (TEA) to evaluate the feasibility of producing biomethane, at a WWTP, through upgrading biogas with a double-stage permeation membrane plant. The biogas was originally generated from the AD of a mixture of primary sludge (PS) and either raw or pre-treated waste activated sludge (WAS), where biological or thermo-alkali pre-treatments were applied to increase the WAS intrinsic low degradability. The TEA was supported by the results of pilot-scale tests, carried out on WAS, which mimicked (i) a traditional mesophilic AD process; (ii) a two-stage AD process, where a temperature-phased anaerobic digestion (TPAD, 3 days, 55 degrees C + 20 days, 38 degrees C) was performed to biologically pre-treat WAS; (iii) a traditional mesophilic AD process preceded by a thermo-alkali (4 g NaOH/100 g TS, 90 degrees C, 90 min) pre-treatment. The TEA was carried out in two phases. In the first, the minimum size of the WWTP capable of making the costs necessary for the implementation of the biogas upgrading plant equal to the revenues coming from selling biomethane (at 62 /MWh) in 10 years was calculated in the absence of pre-treatments. It resulted of 500,000 equivalent inhabitants (e.i.). In the second phase, for the WWTP size found previously, the effect of either biological or thermo-alkali pre-treatments on the economic balance was evaluated, that is the gain (or the loss) associated to the selling of biomethane, compared to the reference price of 62 /MWh. It was found that the TPAD increased the biogas productivity by only 23.6%, too little to compensate the amount of heat necessary for the pre-treatment and the purchase cost of the additional reactor. Conversely, the thermo-alkali pre-treatment, which enhanced the WAS biogas productivity by 110%, increased the biomethane revenues by approx. 10 /MWh, compared to the scenario without pre-treatments. This study offers useful data to WWTP managers who want to introduce WAS pre-treatments, combined with interventions for biogas upgrading, in a new or existing sludge line of a WWTP
Leaching behavior of metals from asphalt mixtures modified with crumb rubber from scrap tires
Full text linkThere are concerns about the potential toxicity of bitumen and recycled materials such as reclaimed asphalt pavements from end-of-life roads and crumb rubber from scrap tires used in asphalt mixtures because they contain metals that may be released into the groundwater. This study investigated the potential metal leaching of laboratory-prepared asphalt mixtures modified with polymer coated rubber (PCR) with wet and dry technology, devulcanized rubber (DVR), compared to an unmodified control mixture and a blend modified with a synthetic polymer (SBS). The objectives were to i) quantify concentrations of metals released, ii) calculate the flux rate, the cumulative mass release, and the assessment ratio for each metal, iii) verify if the metals exceeded the EPA drinking water limit, and, finally, iv) assess the source of metals release. Zinc had the highest concentration among all metals and was present in eluates from all mixtures. The cumulative zinc concentration from DVR mixture was 41% and 34% higher than the control and SBS mixtures, respectively. For PCR wet, the cumulative zinc concentration was 9% higher than the control blend and 1% lower than the SBS mix. The assessment ratio indicated that all metal concentrations would not exceed the drinking water limit, except for zinc, for which further evaluations were required. The main source of zinc may derive from aggregates. This work showed that crumb rubber might not be the only source of metal leaching, and its use in asphalt pavements does not cause a metal leaching higher than other materials
Optimization of the water treatment process in an Italian winery: A case study
Full text linkWater is an essential ingredient in wine production. The winery plant considered in this study, located in the Langhe area (Piedmont, NW Italy), used approx.100,000 m(3) per year of high quality water for cleaning and sanitation operations. Water was collected from the local shallow aquifer and contained high concentrations of dissolved iron (Fe(II), 800-3500 mu g/L) and manganese (Mn(II), 300-700 mu g/L). The water treatment plant (WTP) owned by the winery included a series of treatment processes (air sparging and sodium hypochlorite injection, settling, filtration on a quartzite - pyrolusite filter, removal of excess chlorine with an activated carbon filter and, finally, microfiltration and reverse osmosis, RO) that were deemed to be adequate to make the groundwater compliant with potable uses. However, a survey carried out by the authors revealed the presence of two critical issues in the WTP's management, concerning the Fe(II) and Mn(II) oxidation and removal, and the backwashing of the dual media filter. Firstly, the results of pilot tests demonstrated that the process of air sparging was sufficient for the oxidation of iron and that NaClO was not necessary for that operation. The present concentration of pure oxidant, of 21.5 mg NaClO/L, could be reduced by at least 75 %, without altering the capacity of the WTP in the removal of the two metals. Secondly, a new combination of water fluxes could improve the efficiency of the dual media filter backwashing, thus allowing to simultaneously avoid the use of the RO corrosive concentrate and to minimize the use of high quality water.In the end, a very basic cost model was used to compare the unit cost for water treatment in the current scenario and after the introduction of the two proposed solutions. Specifically, that model considered three cost items: operating costs (that included four sub-items: mortgage, maintenance, consulting and cost for nonamortizable raw materials and consumable), the costs for the purchase of the chemicals necessary for the water treatment process, and the energy costs. The results coming from the application of the cost model demonstrated that the introduction of the proposed solutions into the WTP, at no additional costs, had an undeniable positive impact on the final unit cost of the treated water, that was reduced by 20 %
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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