Dyestuff wastewater treatment using chemical oxidation,physical adsorption and fixed bed biofilm process

Fenton’s oxidation and activated carbon adsorption were examined as pretreatment processes for dyestuff wastewater having high salinity, colour, and non-biodegradable organic concentrations. In this work, each wastewater stream produced by individual production processes was classified as streams R1, R2, and R3. The stream having a value of BOD₅/COD lower than 0.4 was pretreated by Fenton’s oxidation or activated carbon adsorption to increase the ratio of BOD₅/COD which indicates biodegradability. For Fenton’s oxidation with one stream having a value of BOD₅/COD lower than 0.4, the optimal reaction pH was 3.0 and the minimum dosing concentration (mg l⁻¹) of H₂O₂:FeSO₄·7H₂O was 700:3500. Stream R3, which consisted mainly of methanol was efficiently treated by activated carbon adsorption. The ratio of BOD₅/COD was also increased to 0.432 and 0.31 from 0.06 in Fenton’s oxidation and activated carbon adsorption, respectively. A biological treatment system using a fixed bed reactor was also investigated to enhance biological treatment efficiency at various hydraulic retention times, pretreatment conditions by Fenton’s reagent and salt concentrations by dyestuff wastewater. In addition, the efficiency of Fenton’s oxidation as a post-treatment system was also investigated to present a total treatment process of dyestuff wastewater. As the influent COD and salinity were increased, the effluent SS and COD were consequently increased. However, as the microorganisms became adapted to the changed influent condition, the treatment efficiency of the fixed bed reactor quickly recovered under the high COD and salinity since the microorganisms were well adapted to toxic influent conditions. A wastewater treatment process consisting of chemical oxidation, activated carbon adsorption, fixed bed biofilm process and Fenton’s oxidation as a post-treatment system can be useful to treat dyestuff wastewater having high salinity, colour, and non-biodegradable organic concentration.     

Effects of pH amendment on metal working fluid wastewater biological treatment using a defined bacterial consortium

The aim of this study was to determine whether pH amendment of a highly alkaline metal working fluid (MWF) wastewater would improve biological treatment in a bioreactor system following introduction of a bacterial inoculum (comprised of the following strains: Agrobacterium radiobacter, Comamonas testosteroni, Methylobacterium mesophilicum, Microbacterium esteraromaticum, and Microbacterium saperdae). The pH values tested were 6, 7, 8, and 9. Three replicate batch mode bioreactors inoculated with the bacterial inoculum (plus an abiotic control bioreactor) were operated for each of the four pH conditions. After 14 days, the final mean chemical oxygen demand (COD) reduction at pH 9 was 50 +/- 1.4%; at pH 8, 58 +/- 1.4%; pH 7, 65 +/- 1.0%; and pH 6, 75 +/- 2.7% of the initial COD (approximately 10,000 mg L(-1)), respectively. Interestingly, within 5 days, the pH in all inoculated bioreactors progressed toward pH 8. However, all abiotic control bioreactors remained at the pH at which they were amended. The fate of the inoculum, determined by denaturing gradient gel electrophoresis (DGGE) and by cluster analysis of the resulting DGGE profiles, revealed that the inocula survived throughout operation of all pH-amended bioreactors. Length-heterogeneity polymerase chain reaction (PCR) was used to track the population dynamics of individual strains. After 7 days of operation, M. esteraromaticum was the most abundant population in all bioreactors, regardless of pH. From our findings, it appears necessary to adjust the MWF wastewater from pH 9 to between 6 and 7, to achieve optimal biological treatment rates.     

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.     

Temporal dynamics and degradation activity of an bacterial inoculum for treating waste metal-working fluid

In order for established bioreactors to be effective for treating chemically mixed wastes such as metal working fluids (MWF) it is essential that they harbour microbial populations that can maintain sufficient active biomass and degrade each of the chemical constituents present. In this study we investigated the effectiveness of a bacterial consortium composed of four species (Clavibacter michiganensis, Methylobacterium mesophilicum, Rhodococcus erythropolis and Pseudomonas putida), assembled on the basis of their apparent ubiquity in waste MWF, degradation ability and tolerance to fluctuating chemistry of the waste. The temporal dynamics of the inoculum and its effects on the fate of individual chemical components of the waste were studied, by regular sampling, over 400 h. Using a complementary approach of culture with chemotaxonomic (FAME) analysis and applying group specific probes (FISH), the inoculum was found to represent a significant component of the community in bioreactors with and without presence of indigenous MWF populations. In addition, the reduction in the COD by the consortium was approximately 85% of the total pollution load, and 30-40% more effectively than any other treatment (indigenous MWF community alone or activated sludge). Furthermore, all the chemical constituents, including the biocide (a formaldehyde release agent) demonstrated > 60% reduction. Many chemical components of the MWF proved to be recalcitrant in the other treatments. The results of this study confirm that assemblage of an inoculum, based on a comprehensive knowledge of the indigenous microbial community, in the target habitat, is a highly effective way of selecting microbial populations for bioaugmentation of bioreactors.     

The effect of pretreatment on anaerobic activity of olive mill wastewater using batch and continuous systems

This study was focused on several physico-chemical and biological treatment methods that may affect the reduction of the organic load in olive mill wastewater (OMW). In this study, removal of 95% of the phenolic compounds present in OMW was achieved using sand filtration and subsequent treatment with powdered activated carbon in a batch system. This pretreatment for OMW was found to enhance the anaerobic activity of the sludge in the batch system significantly. The efficiency of organic load removal achieved by the anaerobic treatment of untreated OMW in batch reactors with tap water dilution factors below 1:10, reached approximately 65% chemical oxygen demand (COD) removal. However, in the up-flow sludge anaerobic blanket (UASB) reactor, COD removal efficiency of 80–85% was reached at a hydraulic retention time (HRT) of 5 days with an influent COD concentration of 40 g l⁻¹ and organic loading rate (OLR)=8 g⁻¹ COD l⁻¹ per day.     

Biodegradation of naphthalene in the oil refinery wastewater by enriched activated sludge

The main purpose of this paper is to study naphthalene (NAP) biodegradation by acclimated activated sludge, employing the culture-enrichment method in a continuous flow bioreactor of the wastewater treatment process. The effects of various COD loadings and influent flow rates of an artificial wastewater containing 15 mg l⁻¹ NAP on the biodegradation rates of the activated sludge will be investigated, in order to determine the biodegradation kinetics and minimum mean cell residence time of the activated sludge. From the experimental results, it was found that the resulting enriched activated sludge follows the growth rate of the Monod type and can biodegrade those COD and NAP loadings in the influents efficiently, and its bio-treatment efficiency on NAPs increases with the decrease of influent flow rate. The sludge volume index (SVI) of the resulting enriched activated sludge meets the design value required by the convectional activated sludge process for the treatment of wastewater.     

Potential treatment alternative for laboratory effluents

The Chemical Analysis Laboratory under study weekly generates 46.5 L effluent with low pH (0.7), high COD concentration (6535 mg O2/L), sulphate (10390 mg/L) and heavy metals (213 mg Hg/L, 55 mg Cr/L, 28 mg Al/L, 22 mg Fe/L, 10mg Cu/L, 4 mg Ag/L). A treatment sequence has been proposed using a physical chemical step (coagulation/flocculation or chemical precipitation) followed by a biological step (anaerobic treatment). Removals of COD (18%), turbidity (76%) and heavy metals (64-99%) were attained only after adjusting pH to 6.5, without requiring the addition of Al2(SO4)3 and FeCl3. Due to the low COD:sulphate ratio (0.9-1.3), it was possible to efficiently operate the UASB reactor (at the biological step) only upon mixing the effluent with household wastewater. COD, sulphate and heavy metals removals of 60%, 23% and 78% to 100%, respectively, were attained for 30% effluent in the reactor feed. The results pointed to the need of a pretreatment step and mixing the effluent in household wastewater prior to the biological step. This alternative is feasible as this can be achieved using sanitary wastewater generated in the university campus.     

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.     

Enhanced biological phosphorus removal for high-strength wastewater with a low rbCOD:P ratio

In order to assess the feasibility of enhanced biological phosphorus removal (EBPR) for dairy processing wastewater, which in New Zealand have rbCOD:P ratios that can be as low as 13:1, a sequencing batch reactor treating a synthetic wastewater with a COD(VFA) of 800 mg/l (representing a dissolved air flotation (DAF) treated, pre-fermented dairy wastewater with a raw COD of 3000 mg/l) was operated at COD:P ratios of 25:1, 15:1 and 10:1. Full (>99%) phosphate removal was achieved for COD:P loadings of 25:1 and 15:1. The trial using 10:1 COD:P loading showed less consistency but still achieved 82% phosphate removal. Based on further analysis of the final trial this study proposes that the minimum COD:P loading for complete phosphate removal is 13:1 indicating that EBPR could indeed be feasible for effective treatment of dairy processing wastewaters. With regard to the type of COD consumed, propionate was found to be favoured over acetate as a substrate. Further research into increasing the propionate content of pre-fermented dairy wastewaters is suggested.     

Performance of a three-stage aerobic RBC reactor in food canning wastewater treatment

Biological treatment using attached growth in a three-stage lab-scale rotating biological contactor (RBC) was implemented for wastewater from food cannery industries. The wastewater contained high level of organic compounds due to fish and fruit cleaning, cooking and filling processes. Nutrients available in the wastewater enhanced the growth of microorganisms and allowed the biological treatment to be effective. The RBC consisted of 54 parallel discs rotating in a reservoir and was arranged in three stages, i.e. 18 discs oriented in each stage. Effect of major operating and physical variables such as hydraulic retention time (HRT), disc submergence and disc rotational speed were examined in COD removal. For duration of 5 days, 96.4% BOD removal was achieved in batch experiment. BOD constant rate (k) and ultimate BOD were determined respectively, 0.8198 day⁻¹ and 6349 mg/l by Thomas graphical method. COD removal efficiency was increased from 85.3 to 97.4% while the HRT was increased from 24 to 48 h. The COD removal efficiency increased from 74.9 to 87.5% as the disc submergence was increased from 31 to 36%. At submergence level of 23.7%, removal efficiency was increased due to activation of second and third compartments. When the rotational speed was increased from 3 to 11 rpm, the COD removal efficiency was also increased from 62.7 to 93.7%, respectively. The stage COD removal efficiency was gradually decreased with an increase number of stage and about 88% of organic compounds were removed in the first stage of aerobic RBC, indicating that the single stage reactor may be sufficient in practical application.     

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.     

Effect of influent COD/N ratio on biological nitrogen removal (BNR) from high-strength ammonium industrial wastewater

The effect of influent COD/N ratio on biological nitrogen removal (BNR) from high-strength ammonium industrial wastewater was investigated. Experiments were conducted in a modified Ludzack–Ettinger pilot-plant configuration for 365 days. Total nitrification of an influent concentration of 1200 mg NH₄⁺–N l⁻¹ was obtained in this period. Influent COD/N ratios between 0.71 and 3.4 g COD g N⁻¹ were tested by varying the nitrogen loading rate (NLR) supplied to the pilot plant. An exponential decrease of nitrification rate was observed when the influent COD/N ratio increased.

The experimental COD/N ratio for denitrification was 7.1±0.8 g COD g N⁻¹ while the stoichiometric ratio was 4.2 g COD g N⁻¹. This difference is attributable to the oxidation of organic matter in the anoxic reactor with the oxygen of the internal recycle. The influence of influent COD/N ratio on the treatment of high-strength ammonium industrial wastewater can be quantified with these results. The influence of COD/N ratio should be one of the main parameters in the design of biological nitrogen removal processes in industrial wastewater treatment.     

Enhancement of biological treatment performance of saline wastewater by halophilic bacteria

Performances of biological treatment processes of saline wastewater are usually low because of adverse effects of salt on microbial flora. High salt concentrations in wastewater cause plasmolysis and loss of activity of cells resulting in low COD removal efficiencies. In order to improve biological treatment performance of saline wastewater, a halophilic organism Halobacter halobium was used along with activated sludge culture.A synthetic wastewater composed of diluted molasses, urea, KH₂PO₄ and various concentrations of salt (1%–5% NaCl) was treated in an aerobic-biological reactor by fed-batch operation. Activated sludge culture with and without Halobacter were used as seed cultures. Variations of COD removal rate and efficiency with salt concentration were determined for both cultures and results were compared. Inclusion of Halobacter into activated sludge culture resulted in significant improvements in COD removal efficiency. A rate expression including salt inhibition effect was proposed and kinetic constants were determined by using experimental data.This study was supported by the Technical and Scientific Research Council of Turkey.     

Enhanced biological treatment of saline wastewater by using halophilic bacteria

Biological treatment of saline wastewater by conventional activated sludge culture usually results in low removal of chemical oxygen demand (COD) because of plasmolysis of the organisms at high salt concentrations. Since salt removal operations by physicochemical processes before biological treatment are costly, a salt-tolerant organism (Halobacter halobium) was used for effective biological treatment of saline wastewater in this study. Halobacter halobium was used in activated sludge culture for COD removal from saline wastewater (1–5% salt) by fed-batch operation of an aeration tank. Inclusion of Halobacter halobium into activated sludge culture improved the rate and extent of COD removals especially with salt above 2% (w/v).     

Piggery wastewater characterisation for biological nitrogen removal process design

In intensive farming areas, the design of biological nitrogen removal plants for piggery wastewater requires the determination of the chemical oxygen demand (COD) fractions of the effluent. For this purpose, an experimental procedure was developed to quantify the inert soluble (SI) and particulate (XI) COD fractions, as well as the readily (SS) and the slowly (XS) biodegradable COD fractions. For the four wastewaters tested, the SI and the XI fractions were equal to 3-4 g O(2)l(-1) and 17-28 g O(2)l(-1), respectively, which resulted in a total inert fraction of 42-84% of total COD. The SS and the XS fractions were very variable, ranging 0-5 g O(2)l(-1) and 4-25 g O(2)l(-1) respectively, depending on the farm management practices and the storage conditions prior to biological treatment. From these results, the denitrification potential of the piggery wastewaters for biological nitrogen removal treatment could be assessed.     

Evaluation of the efficacy of upflow anaerobic sludge blanket reactor in removal of colour and reduction of COD in real textile wastewater

The upflow anaerobic sludge blanket (UASB) reactor was evaluated for its efficacy in decolourization and reduction in chemical oxygen demand (COD) of real textile wastewater (RTW) under different operational conditions. The efficiency of UASB reactor in reducing COD was found to be over 90%. Over 92% of colour removal due to biodegradation was achieved. The activities of the anaerobic granules were not affected during the treatment of textile wastewater. Cocci-shaped bacteria were the dominant group over Methanothrix like bacteria in textile wastewater treatment. Alkalinity, volatile fatty acids (VFA) content and pH in effluents indicated that the anaerobic process was not inhibited by textile wastewater. It is concluded that UASB reactor system can effectively be used in the treatment of textile wastewater for the removal of colour and in the reduction of COD.     

Assessing the feasibility of achieving biological nutrient removal from wastewater at an Irish food processing factory

In Ireland, wastewaters emanating from the food industry typically contain elevated levels of nitrogen and phosphorus before treatment. Two pilot scale studies were performed to determine the feasibility of achieving biological N and P removal on-site at a food ingredients plant. The wastewater treated by the pilot reactors was that which resulted from the day-to-day production in the full-scale food ingredients plant. Both reactors were of the anaerobic/anoxic/oxic (A/A/O) design, however the sizing of the zones was varied in this study. In the first pilot study, while treating a wastewater of the following strength: 1008 mg COD/l; 30.1 mg NH4-N/l and 26.7 mg P/l, removal efficiencies of 93%, 99% and 98% were obtained for COD, NH4-N and P, respectively. In the second study, while operating at reduced hydraulic retention times and lower recycle rates, the pilot plant treated a wastewater of the following strength: 1757 mg COD/l; 62 mg NH4-N/l and 57 mg P/l, with removal efficiencies of 94%, 97% and 75% obtained for COD, NH4-N and P, respectively. This work showed that biological nutrient removal could be successfully applied to treatment of food industry wastewaters.     

Organics, sulfates and ammonia removal from acrylic fiber manufacturing wastewater using a combined Fenton-UASB (2 phase)-SBR system

A combined Fenton-UASB (2 phase)-SBR system was employed to treat acrylic fiber manufacturing wastewater. The Chemical Oxygen Demand (COD) removal and effluent Biochemical Oxygen Demand (BOD) to COD were 65.5% and 0.529%, respectively, with the optimal Fenton conditions: ferrous was 300 mg/L; hydrogen peroxide was 500 mg/L; pH was 3.0; reaction time was 2.0 h. In two-phase UASB reactor, mesophilic operation (35±0.5 °C) was performed with hydraulic retention time (HRT) varied between 28 and 40 h. The results showed that with the HRT not less than 38 h, COD and sulfate removal were 65% and 75%, respectively. The greatest sizes of granule formed in the sulfate-reducing and methane-producing phases were 5 and 2 mm, respectively. Sulfate-reducing bacteria (SRB) accounted for 35% in the sulfate-reducing phase while methane-producing archaea (MPA) accounted for 72% in the methane-producing phase. During the SBR process, shortcut nitrification was achieved by temperature control of 30 °C.     

Treatment Methods for Wine-Related and Distillery Wastewaters: A Review

A large and increasing volume of wastewater is produced globally by the winery and distillery industries. These wastewaters are generally acidic, high in chemical oxygen demand (COD) and color, and may contain phenolic compounds that can inhibit biological treatment systems. Treatment of distillery and phenolic compound–rich wastewaters by physicochemical, aerobic biological systems and hybrid treatment methods are discussed, as well as products derived from fungal treatment. White-rot fungi have been shown to exhibit unique biodegradation capabilities, primarily due to their production of extracellular and broad substrate range enzymes that are capable of mineralizing lignin, a recalcitrant biopolymer. One of these enzymes, laccase, catalyses the oxidation of various organic compounds with the subsequent reduction of molecular oxygen to water. Laccase synthesis, induction, and inhibition are discussed with the utilization of waste residues for laccase production and the enzyme's potential industrial applications. Distillery wastewaters offer a unique, presterilized, potential growth substrate for the production of lignolytic enzymes such as laccase. Compounds may be utilized for enzyme and biomass production resulting in remediation by the growing fungus.     

UASB/Flash aeration enable complete treatment of municipal wastewater for reuse

A simple, efficient and cost-effective method for municipal wastewater treatment is examined in this paper. The municipal wastewater is treated using an upflow anaerobic sludge bed (UASB) reactor followed by flash aeration (FA) as the post-treatment, without implementing aerobic biological processes. The UASB reactor was operated without recycle, at hydraulic retention time (HRT) of 8 h and achieved consistent removal of BOD, COD and TSS of 60-70% for more than 12 months. The effect of FA on UASB effluent post-treatment was studied at different HRT (15, 30 and 60 min) and dissolved oxygen (DO) concentrations (low DO = 1-2 mg/L and high DO = 5-6 mg/L). The optimum conditions for BOD, COD and sulfide removal were 30-60 min HRT and high DO concentration inside the FA tank. The final effluent after clarification was characterized by BOD and COD values of 28-35 and 50-58 mg/L, respectively. Sulfides were removed by more than 80%, but the fecal coliform only by ~2 log. The UASB followed by FA is a simple and efficient process for municipal wastewater treatment, except for fecal coliform, enabling water and nutrients recycling to agriculture.