Treatment of domestic wastewater by anaerobic denitrification: Influence of the type of support media on the production of extracellular polymer substances (original) (raw)
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Ecological Engineering, 2013
The present work investigates a novel water denitrification technique based on immobilized bacterial biomass using various plastic wastes as supports PVC (polyvinyl chloride), HDPE (high density polyethylene) and LDPE (low density polyethylene) in packed columns. The efficiency of these supports is compared with a conventional support, granular activated carbon (GAC). The results obtained for denitrification under various operating conditions showed that working at a high fluid velocity does not affect the bacterial behavior adversely. The denitrifying bacteria were able to treat water at an inlet nitrate concentration of 600 mg L −1 with removal efficiency near to 100%. The column packed with porous GAC as a support quickly became plugged in contrast to the nonporous LDPE which possesses a rough surface for film support and delivers almost the same performance as GAC. It was found that sulfate ions promote denitrification, but chloride inhibits it. The effectiveness of the packed-bed process is not diminished significantly by the coexistence of both types of ion in the feed stream.
Journal of Urban and Environmental Engineering, 2017
In this study, a heterotrophic denitrification was designed for domestic wastewater treatment with unexpected water flows at different loading rates. Benefited from excellent removal ability COD, shorten operating time and lower maintenance cost. During the time of operation (six months), injection of nitrate was made in the influent RALBI 1 while the RALBI 2 was fed with sewage without addition of nitrate. The COD concentration in the influent of the two reactors was the same. This two reactors (RALBI1 and RALBI2) were fed with real wastewater for 172 days at 6 h HRT, the average COD removal were 71.55% and 54.82% for RALBI1 and RALBI2 respectively. The results showed that RALBI1 has good removal performance for COD compared with RALBI2. This could be due the injected nitrate in RALBI1 whose effect has further stimulated the activity of denitrifying bacteria.
Use of biopolymers as solid substrates for denitrification
Water Science and Technology, 2012
The conventional process to remove nitrate from water, the biological denitrification, uses the addition of dissolved organic carbon that has the potential risk to further deteriorate water quality. Thus, this work aimed to evaluate the specific denitrification activity of a mixed microbial culture and a pure culture of Pseudomonas stutzeri with solid substrates such as polycaprolactone (PCL), polylactic acid (PLA), and starch. The highest nitrate reduction activity was obtained with a microbial mixed culture using starch, 104 mg N 2-N/(g VSS.d), and PCL, 97 mg N 2-N/(g VSS.d), followed by PLA, 53 mg N 2-N/(g VSS.d). A considerable advantage of using biopolymers in water denitrification is the reduced risk of contaminating the water with soluble biodegradable organic carbon.
Ideal bacterial support medium for fixed film denitrification processes/bioreactors must be inexpensive, durable and possess large surface area with sufficient porosity. The present study has been focussed on removing nitrate nitrogen at two different nitrate nitrogen loading rates (60 (NLR I) and 120 (NLR II) mg l-1) from simulated aquaculture wastewater. Coconut coir fibre and a commercially available synthetic reticulated plastic media (Fujino Spirals) were used as packing medium in two independent upflow anaerobic packed bed column reactors. Removal of nitrate nitrogen was studied in correlation with other nutrients (COD, TKN, dissolved orthophosphate). Maximum removal of 97% at NLR-I and 99% at NLR – II of nitrate nitrogen was observed in with either media. Greater consistency in the case of COD removal of upto 81% was observed at NLR II where coconut coir was used as support medium compared to 72% COD removal by Fujino Spirals. The results observed indicate that the organic support medium is just as efficient in nitrate nitrogen removal as conventionally used synthetic support medium. The study is important as it specifically focuses on denitrification of aquaculture wastewater using cheaper organic support medium in anoxic bioreactors for the removal of nitrate nitrogen; which is seldom addressed as a significant problem.
Laboratory-scale solid-phase denitrification (SPD) reactors for nitrate removal were constructed by acclimating activated sludge with poly (L-lactic acid) (PLLA) having weight-average molecular weights (Mw) of 9,900, 12,000, and 45,100 g mol −1. A good nitrate removal rate (3.5–5.3 mg NO3 −-N g [dry wt] −1 h −1) was found in the reactor containing PLLA of 9,900 g mol −1 , whereas the other two reactors with the higher Mw PLLA showed low nitrate removal efficiency. Microbial community dynamics in the low Mw PLLA-acclimated reactor were studied by 16S rRNA gene-targeted PCR-denaturing gradient gel electrophoresis and quinone profiling. Nonmetric multidimensional scaling analyses of these data sets revealed a marked population shift during acclimation of the SPD reactor with low Mw PLLA. The 16S rRNA gene clone library and culture-dependent analyses showed that bacteria belonging to the family Comamonadaceae predominated and played the primary role in denitrification in the PLLA-using reactor; however, none of the bacterial isolates from the reactor degraded PLLA. These results suggest that the nitrate removal property of the PLLA-using SPD reactor is attained through the bioavailability of hydrolysates released abiotically from the solid substrate.
Current Environmental Engineering, 2015
Current studies explore the viability, applicability and comparison of Pseudomonas aeruginosa and Pseudomonas stutzeri based biological denitrification of waters containing high concentration of nitrate and nitrite waste originating from various agricultural and industrial sources. This process converts the readily soluble nitrates to harmless nitrogen gas through a formation of series of intermediates. Experimental work involved use of varying concentration of nitrates and nitrites with different packing conditions, substrates and were analyzed by UV-Vis spectrophotometer. The parameters such as C/N ratio, temperature and pH were optimized for decreasing concentration of nitrates and nitrites. Best packing materials for nitrate reduction proved to be the agro waste based materials which have potential to be used for nitrate reduction of various waste water samples obtained around the city. Average nitrate reduction rates obtained for agro based waste packing condition exhibited about 96.55% and 95% for Pseudomonas aeruginosa and Pseudomonas stutzeri respectively. When applied for denitrification of waste water sample using the obtained reaction parameters, average nitrate reduction obtained was 53.84% and 33.72% for Pseudomonas aeruginosa and Pseudomonas stutzeri respectively. Based on the obtained observations and experimental results, general bioreactor for denitrification process has been designed.
Water Research, 2012
Nitrate Immobilization Activation energy Hyphomicrobium a b s t r a c t This study evaluated the nitrogen removal performance of polyethylene glycol (PEG) gel carriers containing entrapped heterotrophic denitrifying bacteria. A laboratory-scale denitrification reactor was operated for treatment of synthetic nitrate wastewater. The nitrogen removal activity gradually increased in continuous feed experiments, reaching 4.4 kg N m À3 d À1 on day 16 (30 C). A maximum nitrogen removal rate of 5.1 kg N m À3 d À1
DESIGN OF FLUIDIZED BED BIOREACTOR FOR BIOLOGICAL DENITRIFICATION
The effluent waste water from various industries like nitrogenous fertilizer, explosive, paper-pulp industries and also municipal waste contains nitrate as a major pollutant. Nitrate is harmful to mankind, animals and also to the environment. The World Health Organization has set a limit of 10 mg/ l of NO3-for human and 100 mg/l of NO3-for animal consumption. Water above these levels required the denitrification. Biological denitrification of industrial waste water effluent with heterotrophic microorganism has been carried out using fluidized bed bioreactor (FBBR) due to its efficiency and high performance. Experiment were carried out in Fluidized bed bioreactor have much larger surface area per unit volume to support microorganisms, which increases the reactor microorganism concentration. The larger surface area allows shorter hydraulic residence times (HRT) for the same degree of treatment in a given volume. The total removal efficiency was examined for FBBR to the designed parameters such as minimum fluidization velocity, nitrate loading rate, HRT, height of silica sand bed. At anaerobic condition and neutral pH 7, the FBBR were designed which gives 90% nitrate removal efficiency. The objective of the study was to design the fluidized bed bioreactor for maximum denitrification of industrial effluent
PHA based denitrification: Municipal wastewater vs. acetate
Bioresource Technology, 2013
h i g h l i g h t s " PHA based denitrification (PBD) was studied with real wastewater versus acetate. " Focusing on PBD as part of two sludge system assuming chemical removal of residual P. " Highnitrate removal was observed with municipal wastewater (39-53 mg N/L). " Entrapped particulate matter contributed to the reducing power for denitrification. " Low COD/N ratios for denitrification were observed with acetate and wastewater. Denitrification with PHA as the electron donor Two sludge system for wastewater treatment a b s t r a c t Denitrification of municipal wastewater based on bacterial storage polymers-Polyhydroxyalkanoates (PHA) -was investigated in biofilm sequencing batch reactors, as a part of a two sludge system for wastewater treatment and in comparison to acetate based synthetic wastewater. The results show that PHA based denitrification (PBD) of real wastewater can be a viable alternative, especially for wastewater with low COD/N ratio, without the need for external carbon source addition. High nitrate removal capacity of about 40-50 mg N/L with a low COD/N requirement of about 4-5, were observed. It was found that entrapped particulate organic matter contributed additional reducing power, on top of the storage materials, thus allowing for the high nitrate reduction capacity. Daily removal rates were similar to those of extensive treatment systems (0.24-0.31 gr N/L reactorÃd). Large differences in storage yield and composition between biomass grown on synthetic and municipal wastewater were observed.
Water, Air, & Soil Pollution, 2019
Both domestic and industrial effluent treatments contain or produce nitrogen loading during the treatment process. It is important to seek the removal of nitrogen while maintaining the design of existing systems, which are usually composed by the association of anaerobic and aerobic reactors. Thus, in this research, an anaerobic filter (AF) and an upflow anaerobic sludge blanket (UASB) reactors were fed with synthetic effluent enriched with nitrate to compare how these reactors would behave if they became denitrifying reactors. With the application of 100.0 mg NO 3 −-NL −1 , the AF presented better efficiency. With respect to the biogas production, the composition was significantly altered: from CH 4 and CO 2 concentrations close to 70% and 13% without NO 3 N addition to N 2 concentration higher than 85% with addition of 100.0 mg NO 3 −-NL −1. The UASB hydrodynamic profile was modified due to an increase in the mixing behavior along the denitrification stages by biogas production. This was not observed in the AF due to the presence of the support media, which was also responsible for ensuring a greater capacity to withstand denitrification without organic matter being carried out of the system.