Treatment of phosphate-containing oily wastewater by coagulation and microfiltration

The oily wastewater generated from pretreatment unit of electrocoating industry contains oils, phosphate, organic solvents, and surfactants. In order to improve the removal efficiencies of phosphate and oils, to mitigate the membrane fouling, coagulation for ceramic membrane microfiltration of oily wastewater was performed. The results of filtration tests show that the membrane fouling decreased and the permeate flux and quality increased with coagulation as pretreatment. At the coagulant Ca （OH）2 dosage of 900 mg/L, the removal efficiency of phosphate was increased from 46.4% without coagulation to 99.6%; the removal of COD and oils were 97.0% and 99.8%, respectively. And the permeate flux was about 70% greater than that when Ca（OH）2 was not used. The permeate obtained from coagulation and microfiltration can be reused as make-up water, and the recommended operation conditions for pilot and industrial application are transmembrane pressure of 0.10 MPa and cross-flow velocity of 5 m/s. The comparison results show that 0.2 μm ZrO2 microfilter with coagulation could be used to perform the filtration rather than conventional ultrafilter, with very substantial gain in flux and removal efficiency of phosphate.

Efficient removal of Cr(Ⅲ)-carboxyl complex from neutral and high-salinity wastewater by nitrogen doped biomass-based composites

Heavy metals usually exist stably as the species of organic complexes in high-salinity wastewater.Therefore,their effective removal is challenging,especially when the initial p H is neutral.Herein,a novel nitrogen doped biomass-based composite(N-CMCS)was synthesized to remove the complexed heavy metal of Cr(Ⅲ)-carboxyl.The maximum adsorption capacity of Cr(Ⅲ)-Citrate(Cr-Cit)by N-CMCS under neutral p H(7.0)and high-salinity(200 mmol/L NaCl)condition was up to 2.50 mmol/g.And the removal performance remained stable after 6 times of regeneration.Combined with species and characterizations analysis,electrostatic attraction and hydrogen bonding were the main mechanisms for N-CMCS to remove Cr(Ⅲ)-carboxyl complexes.Dynamic adsorption indicated N-CMCS column could treat about 1300BV simulated wastewater and 350 BV actual wastewater with the concentration of effluent lower than1.0 mg/L.Furthermore,N-CMCS could remove a variety of complexed heavy metal ions under neutral p H,indicating the great potential in practical application.

Multistage-batch bipolar membrane electrodialysis for base production from high-salinity wastewater

Bipolar membrane electrodialysis(BMED)is considered a state-of-the-art technology for the conversion of salts into acids and bases.However,the low concentration of base generated from a traditional BMED process may limit the viability of this technology for a large-scale application.Herein,we report an especially designed multistage-batch(two/three-stage-batch)BMED process to increase the base concentration by adjusting different volume ratios in the acid(Vacid),base(Vbase),and salt compartments(Vsalt).The findings indicated that performance of the two-stage-batch with a volume ratio of Vacid:Vbase:Vsalt=1:1:5 was superior in comparison to the threestage-batch with a volume ratio of Vacid:Vbase:Vsalt=1:1:2.Besides,the base concentration could be further increased by exchanging the acid produced in the acid compartment with fresh water in the second stage-batch process.With the two-stage-batch BMED,the maximum concentration of the base can be obtained up to 3.40 mol∙L^(-1),which was higher than the most reported base production by BMED.The low energy consumption and high current efficiency further authenticate that the designed process is reliable,cost-effective,and more productive to convert saline water into valuable industrial commodities.

A heterotrophic nitrification-aerobic denitrification bacterium Halomonas venusta TJPU05 suitable for nitrogen removal from high-salinity wastewater

A novel salt-tolerant heterotrophic nitrification and aerobic denitrification(HN-AD)bacterium was isolated and identified as Halomonas venusta TJPU05(H.venusta TJPU05).The nitrogen removal performance of H.venusta TJPU05 in simulated water(SW)with sole or mixed nitrogen sources and in actual wastewater(AW)with high concentration of salt and nitrogen was investigated.The results showed that 86.12%of NH_(4)^(+)-N,95.68%of NO_(3)^(-)-N,100%of NO_(2)^(-)-N and 84.57%of total nitrogen(TN)could be removed from SW with sole nitrogen sources within 24 h at the utmost.H.venusta TJPU05 could maximally remove 84.06%of NH_(4)^(+)-N,92.33%of NO_(3)^(-)-N,92.9%of NO_(2)^(-)-N and 77.73%of TN from SW with mixed nitrogen source when the salinity was above 8%.The application of H.venusta TJPU05 in treating AW with high salt and high ammonia nitrogen led to removal efficiencies of 50.96%,47.28%and 43.19%for NH_(4)^(+)-N,NO_(3)^(-)-N and TN respectively without any optimization.Furthermore,the activities of nitrogen removal–related enzymes of the strain were also investigated.The successful detection of high level activities of ammonia oxygenase(AMO),hydroxylamine oxidase(HAO),nitrate reductase(NAR)and nitrite reductase(NIR)enzymes under high salinity condition further proved the HN-AD and salt-tolerance capacity of H.venusta TJPU05.These results demonstrated that the H.venusta TJPU05 has great potential in treating high-salinity nitrogenous wastewater.

Life cycle assessment of homogeneous Fenton process as pretreatment for refractory pharmaceutical wastewater

The applicability of the life cycle assessment(LCA)to the Fenton process should be considered not only at the laboratory-scale but also at the full-scale.In this study,the LCA process was applied to evaluate the homo-geneous Fenton process for the treatment of high salinity pharmaceutical wastewater.The potential environmental impacts were calculated using Simapro software implemen-ting the CML 2001 methodology with normalization factors of 1995 world.Foreground data obtained directly from the full-scale wastewater treatment plant and labora-tory were used to conduct a life cycle inventory analysis,ensuring highly accurate results.By normalized results,the Fenton process reveals sensitive indicators,primarily toxi-city indicators(human toxicity,freshwater aquatic toxicity,and marine aquatic toxicity),as well as acidification and eutrophication impacts,contributed by hydrogen peroxide and iron sludge incineration,respectively.Overall,hydrogen peroxide and iron sludge incineration contribute significantly,accounting for at least 78%of these indicators.In sludge treatment phase,treatment of iron mud and infrastructure of hazardous waste incineration plants were the key contributors of environmental impacts,adding up to more than 95%.This study suggests the need to develop efficient oxidation processes and effective iron sludge treatment methods to reduce resource utilization and improve environmental benefits.

Selecting Suitable Heat Source in Refinery for Multi-effect Distillation Based on Grey System Theory

For dealing with high-salinity wastewater in the refinery, the high cost of driving heat source is the disadvantage of multi-effect distillation (MED) so it is of great importance to evaluate the performance of low-temperature heat source for conducting MED and select the optimal temperature for it. Both the MED and the low-temperature heat sources studied in this paper were from a typical refinery located in northwestern China. Besides, a new methodology to evaluate heat sources as the optimal candidate was proposed for MED based on the grey system theory. Five process units, which included 18 fluids of the refinery, were named as the evaluation projects. Three factors, which included safety effects, total costs and characteristics of low-temperature heat sources were determined as the evaluation indexes, the values of which were established through the analyses. The results obtained through the grey correlation analyses have revealed that the grey correlation degrees of these units were 0.661(AVDU), 0.732 (#1 FCCU), 0.618 (#2 FCCU), 0.535 (#1 DCU), and 0.572 (#2 DCU), respectively. Thus, the optimal heat source was provided from #1 FCCU. Through further analyses of the fluids from #1 FCCU, the grey correlation degrees of the fluids were 0.597 (oil and gas at top of tower), 0.714 (recycle oil and gas), and 0.512 (diesel), respectively. Thus, the optimal heat source was the oil and gas recycle stream.