Packed cage rotating biological contactor system for treatment of cyanide wastewater

The aim of this work was to study the efficiency of the packed cage rotating biological contactor (RBC) system with synthetic wastewater (SWW) containing 800 mg/l BOD(5) with various cyanide residue concentrations and hydraulic loading time. The results showed that cyanide had a negative effect to both the system's efficiency and bio-film quality. An increase in cyanide concentration led to a decrease in bio-film growth and the consequent reduction in the removal efficiency of the system. Also, the effluent suspended solids (SS) of the system was increased with increasing cyanide concentrations because the bio-film detached from the media due to the toxicity of the cyanide residue. The system showed the highest COD, BOD(5), TKN and cyanide removal efficiencies of 94.0 +/- 1.6%, 94.8 +/- 0.9%, 59.1 +/- 2.8% and 95.5 +/- 0.6%, respectively, with SWW containing 5 mg/l cyanide under HRT of 8 days, while they were only 88.8 +/- 0.7%, 89.5 +/- 0.5%, 40.3 +/- 1.1% and 93.60 +/- 0.09%, respectively, with SWW containing 40 mg/l cyanide. In addition, the effluent ammonia, nitrite and nitrate were increased with increases in cyanide concentration or loading. However, the system with SWW containing the highest cyanide concentration of 40 mg/l showed almost constant COD and BOD(5) removal efficiencies of 89% and 90%, even when the system was controlled under the lowest HRT of 8 h.     

Effect of flow rate on heavy metal accumulation by rotating biological contactor (RBC) biofilms

Immobilized biofilms are effective in heavy metal removal. The current studies investigated the use of rotating biological contactor (RBC) biofilms in treatment of a wastewater containing cadmium, copper and zinc, each at a concentration of 100 mg L⁻¹. In particular, the influence of hydraulic retention time (HRT) on metal accumulation was studied. Longer HRTs (>12 h) were associated with greater metal removal than short HRTs, particularly with regard to cadmium and zinc. The system was also shown to operate successfully over an extended period of time, at an HRT of 24 h, with removal efficiencies of approximately 34%, 85% and 57% for Cd²⁺, Cu²⁺ and Zn²⁺ respectively after 5–8 weeks contact. Journal of Industrial Microbiology & Biotechnology (2000) 24, 244–250. Received 28 July 1999/ Accepted in revised form 21 December 1999     

Effect of disk rotational speed on heavy metal accumulation by rotating biological contactor (RBC) biofilms

The efficiency of a rotating biological contactor (RBC) in the treatment of waters contaminated with cadmium, copper and zinc, in particular the effect of rotational speed, namely 3, 15 and 25 rev min⁻¹, on heavy metal reclamation was evaluated. Atomic absorption spectrophotometric analysis indicated > 92% and < 20% removal of copper (Cu²⁺) and zinc (Zn²⁺), respectively. Cadmium (Cd²⁺) levels, however, remained constant. Similar results were obtained at all three rotation speeds tested.     

Bacterial community dynamics in a rotating biological contactor treating 2-fluorophenol-containing wastewater

One of the main factors affecting the performance of rotating biological contactors (RBC) is the biofilm characteristics. Therefore, a deep understanding of the microbial population dynamics and structure of the biofilm is mandatory if optimization of organic matter and nutrients removal is targeted. This study focused on the effects of organic shock loads of 2-fluorophenol (2-FP) on the microbial diversity present in an RBC biofilm. The RBC was seeded with activated sludge from a conventional wastewater treatment plant and was operated during 496 days. During the first 126 days, the RBC was subjected to intermittent 2-FP shocks of 25 mg l^?1 and no degradation occurred. Therefore, the reactor was subsequently augmented with a 2-FP-degrading strain (FP1). Afterwards, the RBC had a stable performance when subjected to 2-FP shocks up to 50 mg l^?1 and to a starvation period, as indicated by removal of the compound. Denaturing gradient gel electrophoresis (DGGE) revealed large shifts in microbial communities present in the first and fifth stages, although no clear relation between the sample collection time and spatial factor was found. Phylogenetic affiliation of some predominant members was assessed by direct sequencing of correspondent DGGE bands. Affiliations to α-, β- and δ-Proteobacteria were found. Several bacterial strains isolated from the reactor showed capacity for 2-FP degradation. Strain FP1 was successfully recovered from the biofilm by plating and by DGGE, reinforcing that bioaugmentation was successfully achieved.     

Simultaneous removal of carbon and nitrogen from municipal-type synthetic wastewater using net-like rotating biological contactor (NRBC)

The treatment of municipal-type synthetic wastewater was carried out using a three stages net-like rotating biological contactor (NRBC). The results indicated that, compared with conventional rotating biological contactor (RBC), NRBC have several advantages, such as quick start-up, high biomass concentration and can handle high organic loading rates. The COD and total nitrogen removal rates achieved were 78.8–89.7% and 40.2–61.4%, respectively, in aerobic treatment of low COD municipal-type wastewater at hydraulic retention times (HRT) from 5 to 9 h. The COD removal rate achieved 80–95% when organic loading varied between 16 and 40 gCOD/m² d. A large amount of nematodes were found in the NRBC system, which made the NRBC system produce relatively low amounts of waste sludge, due to their grazing.     

Characterization of filamentous microorganisms in rotating biological contactor biofilms of wastewater treatment plants

Filamentous microorganisms populations present in biofilms from three wastewater treatment plants with a rotating biological contactor system have been studied. Results showed that filaments are an integral component of the biofilms, and that they were made up by: Beggiatoa ssp., Haliscomenobacter hydrossis, Sphaerotilus natans, Thiothrix ssp., and the 021N, 0803, 0914, 0961, 1701, 1851, and 1863 Eikelboom's types. Beggiatoa ssp. was the most frequent microorganism followed by S. natans and type 021N. Microthrix parvicella, Gordona amarae (=Nocardia amarae), Nostocoida limicola (I, II, III), and 0041, 0092, 0211, 0411, 0581, 0675, 1702, and 1852 Eikelboom's types appear infrequently.     

Bioaugmentation of a rotating biological contactor for degradation of 2-fluorophenol

The performance of a laboratory scale rotating biological contactor (RBC) towards shock loadings of 2-fluorophenol (2-FP) was investigated. During a period of ca. 2 months organic shock loadings of 25 mg L?1 of 2-FP were applied to the RBC. As no biodegradation of 2-FP was observed, bioaugmentation of the RBC with a 2-FP degrading strain was carried out and, along ca. 6 months, organic shock loadings within a range of 25-200 mg L?1 of 2-FP were applied. Complete biodegradation of 50 mg L?1 of 2-FP was observed during operation of the reactor. The RBC showed to be robust towards starvation periods, as after ca. 1month of non-supply of the target compound, the reactor resumed 2-FP degradation. The inoculated strain was retained within the biofilm in the disks, as the 2-FP degrading strain was recovered from the biofilm by the end of the experiment, thus bioaugmentation was successfully achieved.     

Influence of nickel (II) and chromium (VI) on the laboratory scale rotating biological contactor

High concentration of heavy metals is toxic for most microorganisms and cause strict damage in wastewater treatment operations and often a physico-chemical pretreatment prior to biological treatment is considered necessary. However, in this study it has been shown that biological systems can adapt to Ni (II) and Cr (VI) when their concentration is below 10 and 20 mg/L, respectively. The aim of this study was to evaluate the effect of Ni (II) and Cr (VI) on the lab-scale rotating biological contactor process. It was found that, addition of Ni (II) up to 10 mg/L did not reduce the chemical oxygen demand removal efficiency and on the contrary concentrations below 10 mg/L improved the performance. The influent Ni (II) concentration of 1 mg/L was the concentration where the treatment efficiency produced a maximum COD removal of 86.5%. Moreover, Ni (II) concentration above 10 mg/L was relatively toxic to the system and produced lower treatment efficiencies than the baseline study without Ni (II). Turbidity and suspended solids removals were not stimulated to a great extent with nickel. Addition of Ni (II) did not seem to affect the pH of the system during treatment. The dissolved oxygen concentration did not drop below 4 mg/L at all concentrations of Ni (II) indicating aerobic conditions prevailed in the system. Experiments conducted with Cr (VI) revealed that addition of Cr (VI) up to 20 mg/L did not reduce the COD removal efficiency and on the contrary concentrations below 20 mg/L improved the performance. The influent Cr (VI) concentration of 1 mg/L was the concentration where the treatment efficiency produced a maximum COD removal of 88%. Turbidity and SS removals were more efficient at 5 mg/L Cr (VI) concentration, rather than 1 mg/L, which lead to the conclusion that 5 mg/L Cr (VI) concentration is the optimum concentration, in terms of COD, turbidity and SS removals. Similar with Ni (II) experiments, addition of Cr (VI) did not significantly affect the pH value of the effluent. The DO concentration remained above 5 mg/L.     

Treatment of heavy metal-polluted wastewaters using the biofilms of a multistage rotating biological contactor

The ability of the biofilms of a three-stage rotating biological contactor (RBC) to treat wastewater contaminated with cadmium, copper and zinc was investigated. The system successfully removed the metals, in the order Cu > Zn > Cd with removal capacities of approximately 73, 42 and 33% respectively. Analysis of the contribution of each reactor indicated that metal removal was not uniform, with Reactor 1 showing a much higher removal capacity than Reactors 2 and 3. Energy dispersive X-ray spectroscopy (EDS) revealed the presence of all three metals on the surface of the biofilms in all three reactors. Closer inspection of the biofilms, in terms of biomass and biofilm thickness, revealed that the low metal removal in Reactors 2 and 3 was probably attributable to poor biofilm development in these two reactors compared to that in Reactor 1. The poor biofilm development was substantiated by low chemical oxygen demand (COD) removal in the latter two reactors.     

Biological treatment of saline wastewater in a rotating biodisc contactor by using halophilic organisms

Biological treatment of saline wastewater presents unique difficulties as a result of plasmolysis of microorganisms in the presence of salt. Removal of salt from wastewater before biological treatment by reverse osmosis or ion exchange operations are rather expensive. Inclusion of halophilic organisms in activated sludge culture seems to be a more practical approach in biological treatment of saline wastewater. A synthetic wastewater composed of diluted molasses, urea, KH₂PO₄, MgSO₄ and various concentrations of salt (0–5% NaCl) was treated in a rotating biodisc contactor (RBC). A salt tolerant organism Halobacter halobium was added onto activated sludge culture (50%) and used as inoculum. Effects of important process variables such as A/Q ratio, COD loading rate, feed COD concentration, salt concentration and liquid phase aeration on system performance were investigated. An empirical mathematical model describing the system's performance as a function of important process variables was developed and constants were determined by using the experimental data.     

Bioremediation of textile azo dyes by an aerobic bacterial consortium using a rotating biological contactor

The degradation of an azo dye mixture by an aerobic bacterial consortium was studied in a rotating biological reactor. Laterite pebbles of particle size 850 microm to 1.44 mm were fixed on gramophone records using an epoxy resin on which the developed consortium was immobilized. Rate of degradation, BOD, biomass determination, enzymes involved, and fish bioassay were studied. The RBC has a high efficiency for dye degradation even at high dye concentrations (100 microg/mL) and high flow rate (36 L/h) at alkaline pH and salinity conditions normally encountered in the textile effluents. Bioassays (LD-50) using Thilapia fish in treated effluent showed that the percentage mortality was zero over a period of 96 h, whereas the mortality was 100% in untreated dye water within 26 h. Fish bioassay confirms that the effluent from RBC can be discharged safely to the environment.     

Removal of surfactant solubilized polycyclic aromatic hydrocarbons by Phanerochaete chrysosporium in a rotating biological contactor reactor

White rot fungi can oxidize surfactant solubilized polycyclic aromatic hydrocarbons (PAH). The objective of this study was to evaluate the performance of immobilized white rot fungus, Phanerochaete chrysosporium, to remove surfactant Tween 80 solubilized PAH i.e. phenanthrene, pyrene and benzo(alpha)pyrene in a rotating biological contactor (RBC) reactor. Results indicated that the immobilized P. chrysosporium in the RBC reactor system in continuous operation could effectively remove the three tested PAH at specific hydraulic loading rates and concentrations tested for each individual PAH. Batch operation of RBC reactor showed that the immobilized P. chrysosporium was stable and effective for the eight successive batch treatments of PAH in solution medium i.e. PAH removal was greater than 90% after 60 h, although only low levels of ligninolytic enzyme activity were detected. The removal of phenanthrene and pyrene in solution medium has been found to be a first order reaction in batch operation. A mass balance calculation indicated that biological oxidation was the main factor for removal of benzo(alpha)pyrene i.e. 95.7% in the RBC reactor. However, for phenanthrene and pyrene, both biological oxidation (i.e. 49 and 56%, respectively) and RBC disc foam adsorption (i.e. 44 and 34%, respectively) made a significant contribution to the removal of PAH.     

Treatment of high strength distillery wastewater (cherry stillage) by integrated aerobic biological oxidation and ozonation

The performance of integrated aerobic digestion and ozonation for the treatment of high strength distillery wastewater (i.e., cherry stillage) is reported. Experiments were conducted in laboratory batch systems operating in draw and fill mode. For the biological step, activated sludge from a municipal wastewater treatment facility was used as inoculum, showing a high degree of activity to distillery wastewater. Thus, BOD and COD overall conversions of 95% and 82% were achieved, respectively. However, polyphenol content and absorbance at 254 nm (A(254)) could not be reduced more than 35% and 15%, respectively, by means of single biological oxidation. By considering COD as substrate, the aerobic digestion process followed a Contois' model kinetics, from which the maximum specific growth rate of microorganisms (mu(max)) and the inhibition factor, beta, were then evaluated at different conditions of temperature and pH. In the combined process, the effect of a post-ozonation stage was studied. The main goals achieved by the ozonation step were the removal of polyphenols and A(254). Therefore, ozonation was shown to be an appropriate technology to aid aerobic biological oxidation in the treatment of cherry stillage.     

Decolourization of synthetic wastewater containing azo dyes by immobilized Phanerochaete chrysosporium in a continuously operated RBC reactor

A laboratory-scale rotating biological contactor (RBC) reactor with immobilized fungal biomass of Phanerochaete chrysosporium was investigated for its performance in decolourizing synthetic wastewater containing single or mixture of azo dyes, Direct Red-80 (DR-80) and Mordant Blue-9 (MB-9). Decolourization efficiency in the continuously operated bioreactor was studied by varying dye inlet concentration and disc rotation speed at two different wastewater hydraulic retention times (HRTs), i.e. 24and 48 h. Results from the single dye-containing experiments showed that the system could completely decolourize the wastewater for a maximum inlet dye concentration within the range 25–200 mg L⁻¹ and 48 h HRT in the reactor; for an inlet dye concentration above 200 mg L⁻¹, the decolourization efficiency slightly reduced up to 85% for the same HRT. However, wastewater containing DR-80 was found to be decolourized more efficiently compared to that containing MB-9. Further, the effect of increase in the disc rotation speed from 2 to 6 rpm in the study revealed no large differences in the decolourization efficiencies of the wastewaters. Similar results were obtained with wastewater containing the dyes together at various concentration combinations as per the two-level factorial design of experiments. Enzyme activities of lignin peroxidase and manganese peroxidase by the fungus were also analysed in the study, and the results indicated that while DR-80 showed a large negative effect on both the enzymes, MB-9 affected mainly the MnP activity by the fungus.     

Treatment of molasses wastewater by acetogenic bacteria BP103 in sequencing batch reactor (SBR) system

Acetogenic bacteria BP103 cells could be used as the absorbent for melanoidin pigment (MP) and molasses wastewater (MWW). The maximum MP adsorption yield of this strain observed from the dead (autoclaved) cell. It was two times higher than that with resting cells. However, the MP adsorption yield of the strain was 50-60% decreased by acclimatization with the media containing MP. The deteriorated cells (MP-adsorbed cells) could be recovered by washing with 0.1% SDS, 0.1% Tween 80 and 0.1 mol/L NaOH solutions. Among them, 0.1 mol/L NaOH solution was most suitable according to highest elution ability and no-effect to the MP adsorption capacity (The adsorption yield of deteriorated cell was reduced only 10% after washing three times with 0.1 mol/L NaOH solution). In SBR system, the strain showed very low MP removal yield with both molasses wastewater (MWW) from the anaerobic pond (An-MWW) and stillage from an alcohol factory (U-MWW). However, the MP removal yield was increased by supplementation with carbon sources (glucose). Also, the MP removal efficiency was increased with the increase of supplemented-glucose concentration. The highest COD, BOD(5), TKN and MP removal efficiencies of the SBR system with 10 times-diluted An-MWW solution containing 30 g/L glucose under HRT of seven days were 65.2+/-2.5%, 82.8+/-3.4%, 32.1+/-0.8% and 50.2+/-3.7%, respectively. The large molecular weight fraction of MP in both U-MWW and An-MWW solutions were rapidly removed by acetogenic bacteria BP103, while the small molecular weight fractions of MP still remained in the effluent.     

Structure of an oligonucleotide containing a N-(2-deoxy-beta-D-erythro-pentofuranosyl)formamide residue facing a guanine

Formamide residue is a major oxidative DNA damage product from ionizing radiation on thymine residues in DNA. We report NMR and molecular modeling studies on a DNA duplex structure which contains guanine opposite formamide residue. Formamide residue exists as either the cis and trans isomer. For the trans and the cis isomers, we find that guanine and formamide are stacked inside the helix and are hydrogen bonded. The oligonucleotide adopts globally a B form structure for the two isomers. Conformational changes are observed between the two isomers.     

Dynamics of protozoan and metazoan communities in a full scale wastewater treatment plant by rotating biological contactors

Performance of a full-scale wastewater treatment plant by rotating biological contactors (RBC) system was monitored during a year by physico-chemical and microbial characterisation. Six points along wastewater treatment were selected in the plant: three points along the water line (influent, sedimentation tank and effluent) and three points along RBC system (RBC1, RBC2 and RBC3). Although a large seasonal change in the values of physico-chemical parameters was observed, operation of the plant was optimal during all year (90% of removal in BOD5 and SS influent content). Microbial characterisation was approached by determining the structure and dynamics of protozoan and metazoan communities. Protozoa were the most abundant in all stages in the plant, heterotrophic flagellates being the most representative group in the water line and ciliates in the RBC system. The same seasonal preference was only observed for heterotrophic flagellates in the water line and green flagellates in the RBC system, both groups having highest abundances in summer and spring, respectively. Identification of ciliated protozoa populations rendered 58 species of ciliates in the plant. Most of these species are typical of aerobic wastewater treatment systems except three of them, which are cited for the first time in this type of ecosystems: Chaenea stricta, Holosticha mancoidea and Oxytricha lanceolata. Along the water line 34 species were identified, and half of them only appeared occasionally (once in all the study), while along the RBC system biofilms 55 species were observed, and the majority appeared permanently in this system. Our results indicate that the type of habitat, rather than the physico-chemical water parameters, was the primary factor in determining the different distribution of protozoan and metazoan communities in the plant. In RBC biofilms, the structure of ciliate protozoa community was found to be quite sensitive to changes in physico-chemical parameters, mainly to organic loading (BOD5) variations.     

Synthesis of a glycotripeptide and a glycosomatostatin containing the 3-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-L-serine residue

3-O-(2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyl)-N- (tert-butyloxycarbonyl)-L-serine was synthesized and condensed by the solid-phase procedure to give the sequence Gly-[beta-D-GlcpNAc-(1 leads to 3)-Ser]-Ala-OH and beta-D-GlcpNAc-(1 leads to 3)-Ser-13-somatostatin. The synthetic glycopeptides appeared homogeneous on t.l.c. and l.c. examination and showed the correct amino acid composition and 2-amino-2-deoxy-D-glucose content. The structure of Gly-[beta-D-GlcpNAc-(1 leads to 3)-Ser]-Ala-OH was further confirmed by mass spectrometry of the N-acetyl permethyl derivative, and by n.m.r. spectroscopy.     

Synthesis,conformation, and biological activity of two fMLP-OMe analogues containing the new 2-[2′-(methylthio) ethyl] methionine residue

The new C^α-tetrasubstituted α-amino acid residue 2-[2′-(methylthio) ethyl]methionine (Dmt) has been introduced into the reference chemotactic tripeptide HCO-Met-Leu-Phe-OMe (fMLP-OMe) in place of the leucine or methionine, respectively. The biological activity of the new analogues [Dmt²] fMLP-OMe (2) and [Dmt¹] fMLP-OMe (3) has been determined; whereas 2 is active toward human neutrophils, stimulating directed migration, superoxide anion generation, and lysozyme release, 3 results practically inactive in all tested assays. A conformational analysis on 2 and 3 has been performed in solution by using ir absorption and ¹H-nmr. The conformation of 2 was also examined in the crystal by x-ray diffraction methods. Both 2 and 3 adopt fully extended conformation in correspondence with the Dmt residue. Biological and conformational results are discussed and compared with related previously studied models. © 1997 John Wiley & Sons, Inc. Biopoly 42: 415–426, 1997     

Analgesic dipeptide derivatives. II. Synthetic dipeptides containing a C-terminal 2-(2-nitrophenylsulfenyl) tryptophan residue

The syntheses of dipeptide derivatives of the general formula X-Trp(Nps)-OR (R = H or Me; X = Lys, Gly, Ala, Leu, Ser, Glu, His, Arg, Orn, Dpr, Gpr and Har) are described. The analgesic activities of Gpr- and Har-containing dipeptides have been evaluated and, in the light of these results, the influence of the side chain length of the basic amino acid on the analgesic effect is studied.