Rajendra Prasad Singh

Enhanced Nitrogen Removal by Rice Husk Amended Dynamic Membrane Bioreactors

AbstractEffective and low-cost dynamic membrane bioreactors (DMBR) can be a strong option for wastewater treatment in developing countries. The goal of this study was to investigate the effect of rice husk addition on the DMBR’s nitrogen removal performance. Tests were performed at both lab-scale and pilot-scale facilities. Results showed that rice husk served as a suitable biofilm carrier as well as an effective denitrification carbon source. In lab-scale experiments, the removal efficiency of rice husk amended DMBR for chemical oxygen demand (COD), NH3-N, and total nitrogen (TN) was 96.7, 96.3, and 80.4%, respectively. Results from the pilot-scale DMBR system showed that removal efficiency for COD and NH3-N was 90.3 and 95.2%, respectively, whereas TN removal was comparatively lower (50.5%). Fluorescence in situ hybridization (FISH) analysis showed that the bacterial population was higher in the rice husk added DMBR than the controlled DMBR, and ammonia-oxidizing bacteria were the main components of tot...

Adsorption behavior of benzenesulfonic acid by novel weakly basic anion exchange resins

Two novel weakly basic anion exchange resins (SZ-1 and SZ-2) were prepared via the reaction of macroporous chloromethylated polystyrene-divinylbenzene (Cl-PS-DVB) beads with dicyclohexylamine and piperidine, respectively. The physicochemical structures of the resulting resins were characterized using Fourier Transform Infrared Spectroscopy and pore size distribution analysis. The adsorption behavior of SZ-1 and SZ-2 for benzenesulfonic acid (BA) was evaluated, and the common commercial weakly basic anion exchanger D301 was also employed for comparison purpose. Adsorption isotherms and influence of solution pH, temperature and coexisting competitive inorganic salts (Na2SO4 and NaCl) on adsorption behavior were investigated and the optimum desorption agent was obtained. Adsorption isotherms of BA were found to be well represented by the Langmuir model. Thermodynamic parameters involving ΔH, ΔG and ΔS were also calculated and the results indicate that adsorption is an exothermic and spontaneous process. Enhanced selectivity of BA sorption over sulfate on the two novel resins was observed by comparison with the commercial anion exchanger D301. The fact that the tested resins loaded with BA can be efficiently regenerated by NaCl solution indicates the reversible sorption process. From a mechanistic viewpoint, this observation clearly suggests that electrostatic interaction is the predominant adsorption mechanism. Furthermore, results of column tests show that SZ-1 possesses a better adsorption property than D301, which reinforces the feasibility of SZ-1 for potential industrial application.

Pollutant removal efficiency of mesocosm HSSF-constructed wetlands treating highway runoff with different filter materials and HRT

AbstractIn this study, cobble-stone (CS) and broke-stone materials were used as filter media in horizontal sub-surface flow constructed wetlands (HSSF-CWs) for highway runoff treatment. These wetlands were planted with Phragmites spp. plants. The Lukou viaduct section of the Nanjing airport expressway was selected for collection of highway runoff. The HSSF-CWs were subjected to two hydraulic retention times (HRT) of 12 and 24 h with different hydraulic loads and influent flow rate. Based on the results, the CW with broken-stone (BS) substrate achieved significantly higher removal efficiency for SS (75 and 55%), chemical oxygen demand (45 and 50%), NH3-N (78 and 88%), and total phosphorus (77 and 34%) in 12 and 24 h HRT compared with CS substrate wetlands. The CW with CS substrate showed lower removal efficiencies than the BS substrate wetland. The removal efficiencies for Cu, Zn, and Pb for the 12 h HRT were 62, 80, and 9%, respectively, and the concentrations of Cu, Zn, Pb, and Cr were generally under th...

Investigation on the carbon sequestration capacity of vegetation along a heavy traffic load expressway

Carbon sequestration by vegetation plays an important role in the global carbon cycle. More emphasis on the carbon sequestration of roadside vegetation will help to reduce the total carbon emissions from the transportation sector. In the current study, the Shanghai-Nanjing G42 expressway in east China was selected to investigate and calculate the carbon sequestration of roadside vegetation including trees, shrubs and herbs. Findings of the current study revealed that the total carbon sequestration of all the vegetation was about 97,000 tons per year. Results also indicated that trees have a higher carbon sequestration capacity (γ) in unit land area compared to shrubs and herbs. The γ value of most of the shrubs was lower than that of tree; however, species such as Nerium indicum, Jasminum mesnyi and Forsythia suspense have better carbon sequestration capacity than some other tree species. The γ value of herbs was too low, compared with trees and shrubs. The findings of the current study will be of great benefit to make the vegetation planting strategy for express highways in the areas with similar geographic characteristics and climate.

Sediment in-situ bioremediation by immobilized microbial activated beads: Pilot-scale study

A field study was carried out to investigate the sediment in-situ bioremediation by adding microbial activated beads. In this work, Calcium carbonate, silicon dioxide, activated carbon powder, attapulgite powder, sodium alginate, microbial liquid and polyvinyl alcohol were utilized to make the immobilized microbial activated beads. Field experiment results showed that the removal rate of NH4+-N, TN and COD in overlying water reached about 61.8%, 87.5% and 87.1%, respectively. The initial concentration of NH4+-N, TN and COD was 159 mg/L, 6.24 mg/L and 7.28 mg/L, whereas and the final concentration was 58 mg/L, 0.78 mg/L and 0.94 mg/L when water temperature, DO, pH and C/N ratio were 25-30 °C, 2-3 mg/L, 7.0-8.0 and 10-15, respectively. Moreover, under optimal temperature condition (25-30 °C), the removal rate of TOC, TN, heterotrophic bacteria and sulfur bacteria in the river sediment reached to 46.5%, 50.7%, 39.2% and 73.2%, respectively.

Impact of tryptophan on the formation of TCNM in the process of UV/chlorine disinfection

Low-pressure (LP) UV treatment after chlorine disinfection was associated with enhanced formation of trichloronitromethane (TCNM), a halonitromethane disinfection by-product (DBP), due to the chlorination of tryptophan. Evidence was found that the concentration of TCNM from tryptophan increased quickly to the maximum for the first instance. Moreover, the increase of TCNM under UV exceeded 10 times than under dark. Then, it was found to have an obvious decrease in the formation of TCNM, even finally hardly disappear. In order to elucidate reasons for this phenomenon, the effects of light intensity, initial tryptophan concentration, free chlorine concentration, pH, and tert-butanol (TBA) on the formation of TCNM were investigated under UV/chlorine treatment. Finally, the effects of tryptophan on the formation of TCNM and the direct photodegradation of TCNM under LP UV irradiation were studied for analyzing the possible pathways of TCNM formation from amino acid. Since amino acids are very common in water sources, further research into chemical oxidation of these species by LP UV and chlorine is recommended. It can help us to find the precursors of TCNM formation and reduce the risk of TCNM formation for drinking water and wastewater utilities.

WITHDRAWN: Formation of TCNM from polyDADMAC during UV irradiation combined with chlorination treatment.

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