Her constant encouragement throughout the phase of my research work with her full involvement was truly admirable. I am very grateful to my beloved husband Anand for his support, encouragement, calm patience and guidance during my research work. The concentration of SCN of 54-400 mg/L in the influent did not cause significant inhibitory effect on the removal of phenol, thiocyanate and COD in R2/B2; however, the highest concentration of phenol (above 468 mg/L in R2 and 511 mg/L in B2) showed negative effect on SCN removal.
Both the CMBR and FMBR systems successfully reduced phenol, thiocyanate, and COD to discharge levels.
Materials and Methods
24 4.9 (a) Performance of aerobic CMBR (R3) by variation in the phenol concentration of the feed. b) Performance of aerobic MBR (R3) by variation in the phenol concentration of the feed. 54 4.27 (a) Performance of aerobic FMBR (B3) by variation in the phenol concentration of the feed. b) Performance of aerobic FMBR (B3) by variation in the phenol concentration of the feed. 30 4.23 Effect of feed phenol on CMBR system performance (Solid line removal; dashed line fraction of TN remaining in effluent).
79 4.67 Overall FMBR efficiency at different phenol concentrations Pollutant profile in FMBR at different feed pyridine concentrations (a).
INTRODUCTION
It is reported that biodegradation is a reliable option for the treatment of wastewater containing phenol and thiocyanate (Fang et al. Anaerobic reactor can act as partial removal of organic matter such as phenol and COD and helps in rapid oxidation by downstream process of treatment (Yu et al. 1996) Modification of suspended growth reactors with additional media to support microbial growth has proven to be very suitable for the treatment of various industrial effluents (Johnson et al. 2000; Sigrun et al. 2002 ).
Most studies with phenol, SCN- and NH4+-N used reactors with continuous mode of operation in suspended growth system or fixed growth system (Chakraborty and Veeramani, 2006; Jeong and Chung, 2006a-b; Zhao et al. 2009).
Organization of the Thesis
Fed batch operation of biological reactor is a promising method for treating high strength and/or toxic wastewater (Bali and Sengul, 2002). In this study, moving bed reactor (MBR) was operated with mixed microbial culture in the presence of several pollutants such as phenol, thiocyanate and NH4+. N at different pollutant loads and operating conditions to evaluate the performance of the MBR system.
The study was conducted in both an anaerobic-anoxic-aerobic continuous moving bed reactor (CMBR) and a fed batch moving bed reactor (FMBR) system.
LITERATURE REVIEW
TYPE OF WASTEWATER
CHARACTERISTICS AND TOXICITY OF POLLUTANTS
- Phenol (C 5 H 5 OH)
- Thiocyanate (SCN - )
- Ammonia-nitrogen, Nitrate and Nitrite-nitrogen
- Pyridine (C 5 H 5 N)
- Permissible limit for pollutants for discharging into water body
Thiocyanate is a very stable compound and therefore difficult to destroy (Boucabeille et al. 1994), and its toxicity increases at high concentrations (more than 0.3 g/L as SCN-). In addition, thiocyanate is reported to be toxic to microorganisms at relatively low concentrations of 58–116 mg/L (Wood et al. 1998). A concentration greater than 15 mg SCN-/100 ml in mammalian blood has been reported to be critically toxic (Paruchuri et al. 1990).
Nitrite-nitrogen (NO2--N) is a highly toxic compound for fish, benthic fauna, plants, bacteria, plankton, nitrifiers and methanogens (De Beer et al. 1997).
TREATMENT TECHNOLOGIES FOR REMOVALS OF PHENOL, THIOCYANATE, AMMONIA-N, NITRATE-N AND PYRIDINE
- Physicochemical processes
- Limitations of physicochemical treatment techniques
- Biological treatment process
- Biodegradation of Pollutant
- Phenol biodegradation
- Thiocyanate degradation
- Nitrogen removal (a) Ammonia
- Pyridine degradation
- Bioreactors used for treatment of pollutants in single and combination
- Suspended growth system A. Suspended growth aerobic reactor
Removal of phenol by ozonation has been reported in many literatures (Chang et al. 2008; Amin et al. 2010). For example, complete denitrification requires 2.47 g of methanol per gram of nitrate nitrogen (McCarty et al. 1969). Two general strategies for bacterial pyridine degradation include (i) hydroxylation reactions followed by reduction, and (ii) (aerobic) reduction pathway not initiated by hydroxylations (Kaiser et al. 1996).
Pyridine and its derivatives are reported to be toxic to the anaerobic process (Gijzen et al. 2000).
Suspended growth anaerobic reactor
The best results were obtained when the HRT was 98 and 86 hours for first step and second step ASP, respectively. The most obvious problems faced by conventional ASP systems used for the treatment of phenol, thiocyanate and ammonia in combination are the toxicity and inhibitory nature of the pollutants towards each other, leaching of biomass, poor settling ability due to the appearance of filamentous microorganisms, inhibition of nitrifiers. by toxic compounds, high oxygen consumption and energy demand leading to high operating costs and many times ammonia inhibition. Thus, conventional single-phase activated sludge process is insufficient to handle this wastewater (Vázquez et al.
The addition of 2,4-dinitrophenol, carbonyl cyanide m-chlorophenylhydrazone (CCCP) and mercuric chloride (Hg2Cl2) completely inhibited the activity of the ammonium oxidizing sludge.
Anoxic reactor
Sequencing Batch Reactor (SBR)
- Attached growth system
- Sequential bioreactor system
- SUBSTRATE REMOVAL KINETICS
- Haldane’ inhibition model
- Modified Stover-Kincannon model
- Inhibition kinetics due to toxicity
- Grau second order kinetic model
- First order kinetic model
- OBJECTIVE AND SCOPE OF THE STUDY
The support can be the wall of the reactor, barriers designed for this purpose, etc. (Ødegaard et al. 2006). Biofilm processes have been shown to be reliable in removing organic carbon and nitrogen without some of the problems caused by activated sludge processes (Yang et al. 2009). The activity of the biofilm involved in the degradation of phenol was almost eight times higher than the activity of the suspended biomass.
The aim of the study is to evaluate the performance of anaerobic-anoxic-aerobic moving bed reactors while treating high concentrations of phenol, SCN─, NH4+-N and pyridine from simulated industrial wastewater using continuous and fed batch reactor systems.
MATERIALS AND METHODS
Materials
- Chemicals and Reagents
- Biomass support material: Sponge cubes
The porosity of the sponge was estimated from the ratio of the void volume to the volume of the sample sponge. For sponge density analysis, the weights of five sponge cubes, ten sponge cubes, and twenty sponge cubes were taken for the average weight of each sponge cube. The sponge cube was cut into 1 cm3 (1 cm x 1 cm x 1 cm) with six sides, with each cube having an area of 6 cm2.
Approximately 120 g of oven-dried sponge cube was placed in each CMBR reactor and 100 g of sponge was manually added to FMBR, more or less uniformly in layers starting from the bottom.
Experimental Methodologies
- Seed sludge
- Synthetic feed
- Reactor operation
- Continuous moving bed reactor (CMBR) .1 Acclimatization of CMBR
- Fed batch moving bed reactor (FMBR) .1 Acclimatization of culture
- Substrate removal kinetics study in CMBR and FMBR
- Performance of the moving bed systems at shock load
- Treatment of real wastewater
Steady state data were collected for 12–15 days and considered to analyze the performance of each reactor. Because of this, anoxic reactor was acclimatized up to maximum phenolic concentration of 1250 mg/L, 50 mg/L SCN- and. In aerobic reactors (R5A and R6A), a sponge of 60 g was added to each reactor in 5 liters of screened wastewater.
The working volume (liquid, sponge and biomass) of each reactor was made 15 L with tap water. In each 15 L reactor, the total amount of sponge cubes was 120 g, and the total sponge cube volume in each reactor was 2360 cm3, which was 15.7% of the working volume of each reactor, giving the number of sponge cubes in each reactor as 2353. The mixed liquor from each reactor was allowed to flow into the clarifier for settling biomass.
The performance of the CMBR was also evaluated by varying the hydraulic retention time (HRT) from 3-8 days at constant supply of phenol, thiocyanate and ammonia concentrations of 2500 mg/L, 600 mg/L and 500 mg/L, respectively. For anaerobic and anoxic acclimation, 3 liters of sieved seed sludge and 50 g of sponge block were added to each reactor for the immobilization of microbes and the final volume of 5 liters was made by adding tap water. The total volume of sponge cubes in each reactor was 1967 cm3, which was 19.67% of the working volume of each reactor.
When studying the variation of filling time, the decanted volume from B2 and B3 and the filling time were twice that of B1 and the HRT of each reactor was constant (10 days in total). To evaluate the performance of the moving bed reactor system in removing phenolics, pyridine and thiocyanate, two coke oven wastewaters were collected from a coke manufacturing industry in Assam, India.
Analytical Methods .1 Wastewater parameter
- Biomass concentration
- Chemical characteristics of sludge
- Specific methanogenic activity (SMA)
- Enrichment, isolation and identification of microorganisms
Thiocyanate was measured by colorimetric method using ferric nitrate in acidic pH and absorbance was measured at 460 nm. NaOH (5 mM) served as the eluent and sulfuric acid (2.0 mM) as the regenerating agent in the chromatogram analysis. Rinse thoroughly with distilled water and dry at 105oC then ignite at 550oC according to APHA 1998.
During the first days of operation, four sponges were collected from the top (near the outlet) and the middle (one foot below the outlet) of the anaerobic, anoxic, and aerobic reactors and washed with distilled water. SMA analysis was performed with sludge from R1/B1 following a procedure similar to Isa et al. (1997). Feed identical to the synthetic nitrogen-purged feed used in the study with varying concentrations of thiocyanate was added to each bottle of serum.
Two mushroom cubes were randomly collected from each reactor, separately immersed in distilled water for 5 min and scraped with a spatula. This water was then serially diluted with distilled water up to 105 times using the serial dilution method. The identification of microorganisms was carried out by morphological and biochemical tests along with microscopic observations.
In the biochemical test for strain identification, gram reaction test, fermentation test (lactose, dextrose, sucrose and inulin), H2S production, nitrate reduction, indole production, methyl red test, Vogues Proskauer test, catalase tests, oxidase and citrates. . Air Compressor Aeration in Aerobic Reactors Sonee SSY-8 Water Purification System To provide distilled water and.
RESULTS AND DISCUSSION
PERFORMANCE OF SEQUENTIAL ANAEROBIC–ANOXIC–AEROBIC CONTINUOUS MOVING BED REACTOR (CMBR) SYSTEM
- Performance of anaerobic CMBR (R1) at varied feed thiocyanate
- Performance of anoxic CMBR (R2) at varied influent thiocyanate
- Performance of aerobic CMBR (R3) at varied influent thiocyanate
- Overall performance of sequential CMBR system at varied thiocyanate concentration
- Performance of anaerobic CMBR (R1) at HRT variation
- Performance of anoxic CMBR (R2) at HRT variation
- Performance of aerobic CMBR (R3) at HRT variation
- Overall performance of CMBR system at varied HRT
- Effect of feed phenol on performance of anaerobic CMBR (R1)
- Effect of influent phenol concentration on performance of anoxic CMBR (R2) Steady state performance of R2 is shown in Tables 4.8 (a) and (b). Influent phenol to R2
- Effect of influent phenol variation on performance of aerobic CMBR (R3) Average steady state performance of R3 is shown in Tables 4.9 (a) and (b). R3 received a
- Effect of feed phenol on overall performance of CMBR system
- Effect of feed ammonia–nitrogen on performance of anaerobic CMBR (R1) Steady state performance of R1 at varied influent NH 4 + –N concentrations is presented in
- Effect of varied influent ammonia concentration on anoxic CMBR (R2)
- Effect of varied influent ammonia concentration on aerobic CMBR (R3)
- Overall performance of three–stage CMBR at ammonia-N variation
- Aerobic reactor (R3)
Figure 4.3 shows fractional removals of feed SCN–, feed phenol and feed COD by R1. However, R1 only played a significant role in the fractional removal of phenol and COD in the feed when the SCN value of the feed was low. During the dietary SCN variation study, it was observed that the biomass concentration in R3 increased from 9845 mg/L to 12667 mg/L when a higher amount of COD and NH4+–N entered R3.
The ratio was found to decrease drastically to 3.5 with increasing influent SCN – to 122 mg/L in R3. The overall performance at different SCN– feed concentrations is shown in Figure 4.7 in terms of COD, SCN–, NH4+–N and phenol removal. It can be seen that the removal of phenol and SCN- was complete and independent of the concentration of dietary SCN.
The present result shows that the effect of feed SCN– on phenol and COD removal in anaerobic reactors was very profound. Besides phenol, COD and SCN–, no removal of NH4+–N was observed in R1 at all HRT levels. Sulfate formation with removal of SCN- in R3 at all levels of HRT was observed.
Together with NH4+–N entering from the effluent of R1 and recycling from R3, a certain amount of NH4+–N was generated by the degradation of SCN– in R2. R1 showed moderate removal of phenol and COD, while no removal of SCN– or NH4+–N was observed. It is clear that the removal of phenol and SCN– was complete and independent of the NH4+–N concentration in the feed (Figure 4.31).
With the increase in the supply of SCN–/NH4+–N, the influent NH4+–N to R3 also increased, as NH4+–N also resulted from the degradation of thiocyanate in R2 and R3.
PERFORMANCE OF SEQUENTIAL ANAEROBIC–ANOXIC–AEROBIC FED BATCH MOVING BED RECTOR (FMBR) SYSTEM
- Performance of anaerobic FMBR (B1) at varied feed thiocyanate
- Performance of anoxic FMBR (B2) at varied influent thiocyanate
- Performance of aerobic FMBR (B3) at varied influent thiocyanate
- Overall performance of FMBR at varied feed thiocyanate
- Performance of anaerobic FMBR (B1) at varied fill time
- Performance of anoxic FMBR (B2) at varied fill time
- Performance of aerobic FMBR (B3) at varied fill time
- Overall performance of FMBR system at varied fill time
- Performance of anaerobic FMBR (B1) at varied HRT
- Performance of anoxic FMBR (B2) at varied HRT
- Performance of aerobic FMBR (B3) at varied HRT
- Overall performance of FMBR at varied HRT
- Performance of anaerobic FMBR (B1) at varied cycle time
- Performance of anoxic FMBR (B2) at varied cycle time
- Performance of aerobic FMBR (B3) at varied cycle time
- Overall performance of fed batch MBR system at varied cycle time
- Performance of anaerobic FMBR (B1) at phenol variation
With increase in feed SCN–, more amount of NH4+–N was generated due to decomposition of SCN– in B2 and inflow NH4–N to B3 also increased [Table 4.15 (a)]. The NH4+–N removal was 13% under instantaneous loading from the lowest influent concentration of 300 mg/L, and it was 1–4% under gradual loading. This amount increased further with NH4+–N generated from SCN decomposition in B2, and the final influent NH4+–N to B3 was 300–455 mg/L.
The effluent of B3 was recycled to B2 and the NH4 +-N flux to B2 also increased in the short filling time. The influent NH4+-N concentration in the present study was higher than the inhibitory concentration of the substrate during the gradual filling period. During short fill time studies, the system removed lower amounts of NH4-N in B3 but reduced higher NOx-N.
Overall performance of FMBR system in terms of total COD, SCN–, NH4+–N, total nitrogen and phenol removal is presented in Figure 4.55. Similarly, higher NH4+–N removal occurred at higher HRT and it was hindered at lower HRT. B1 showed removal of phenol and COD without any removal of SCN− and NH4+–N during the study.
The ratio of influent COD/NH4+–N in B3 was ~1 at higher cycle time, because almost the same amount of COD and NH4+–N entered B3. The effect of cycle time was significant on NH4+–N removal and increased from 77.6 to 86% as cycle time increased. With an increase in cycle time, the oxidized nitrogen fraction increased from 18 to 28% and the NH4+–N fraction decreased slightly from 6 to 4%.
The increase in oxidized nitrogen and the decrease in NH4+–N was almost negligible over a cycle time of 30 h.
