Reductive transformation and dechlorination of chloronitrobenzenes in UASB reactor enhanced with zero‐valent iron addition

BACKGROUND: Zero‐valent iron (ZVI) is increasingly being applied in biological wastewater treatment to enhance the conversion of various contaminants. The objective of this present study was to investigate the effect of ZVI on the anaerobic biotransformation and dechlorination of chloronitrobenzenes (3,4‐DClNB and 4‐ClNB). Experiments were conducted in two upflow anaerobic sludge blanket (UASB) reactors, one (R2) with 30 g L^?1 ZVI added, and the other (R1), serving as control reactor. RESULTS: ZVI‐based anaerobic granular sludge (ZVI‐AGS) composed of bacteria associated with precipitated FeCO₃ and FeS was successfully developed within 5 months in reactor R2. ZVI addition obviously enhanced 3,4‐DClNB transformation and dechlorination efficiencies under high 3,4‐DClNB loads, and further promoted dechlorination of 4‐chloroaniline (4‐ClAn) to aniline. Compared with the AGS formed in R1 reactor, iron and its corrosion products were observed and colonized with anaerobes such as methanothrix in ZVI‐AGS, and the specific transformation rates of 3,4‐DClNB and 4‐ClNB using ZVI‐AGS were improved by 34.0% and 64.4%, respectively. Furthermore, ZVI‐AGS provided higher 3,4‐dichloronailine and 4‐ClAn dechlorination efficiency than AGS. Abiotic transformation of ClNBs by ZVI, appropriate concentration of iron corrosion products, lower redox potential and greater hydrogen production were the main factors providing enhanced transformation and dechlorination of ClNBs in the UASB reactor. CONCLUSION: Addition of ZVI to a UASB reactor enhanced the reductive transformation and dechlorination of ClNBs. It provides a feasible proposal for the design and optimization of a high‐rate anaerobic wastewater treatment technique for industrial wastewater. Copyright © 2010 Society of Chemical Industry     

Biological Nutrient Removal Using a Novel Laboratory‐Scale Twin Fluidized‐Bed Bioreactor

The capability of biological nutrient removal from wastewater of a novel laboratory‐scale twin fluidized‐bed bioreactor (TFBBR) was studied. The work showed approximately 96 % organic matter, 84 % nitrogen, and 12 % phosphorus removal efficiencies in the first three phases of the study at influent synthetic municipal wastewater (SMW) flow rates of 150, 190, and 240 L/d, with corresponding organic loading rates of 1.3, 1.7, and 2.3 kg COD m^–3 d^–1 and nitrogen loading rates of 0.14, 0.18 and 0.25 kg N m^–3 d^–1. The TFBBR effluent was characterized by <1.0 mg NH₄‐N/L, <4.3 mg NO₃‐N/L, <6 mg TN/L, <6 mg SBOD/L, and 6–10 mg VSS/L. For the three phases, biomass yields of 0.06, 0.066, and 0.071 g VSS/g COD were observed, respectively, which was a significant further reduction in yield compared to the liquid‐solid circulating fluidized‐bed bioreactor technology developed and patented by this research group, of 0.12–0.16 g VSS/g COD. The very low yield was due to a longer solid retention time of 72–108 d.     

The effect of organic loading rate on the anaerobic digestion of two‐phase olive mill solid residue derived from fruits with low ripening index

A study of the effect of organic loading rate on the performance of anaerobic digestion of two‐phase olive mill solid residue (OMSR) was carried out in a laboratory‐scale completely stirred tank reactor. The reactor was operated at an influent substrate concentration of 162 g chemical oxygen demand (COD) dm^?3. The organic loading rate (OLR) varied between 0.8 and 11.0 g COD dm^?3 d^?1. COD removal efficiency decreased from 97.0% to 82.6% when the OLR increased from 0.8 to 8.3 g COD dm^?3 d^?1. It was found that OLRs higher than 9.2 g COD dm^?3 d^?1 favoured process failure, decreasing pH, COD removal efficiency and methane production rates (Q_M). Empirical equations described the effect of OLR on the process stability and the effect of soluble organic matter concentration on the total volatile fatty acids (TVFA)/total alkalinity (TAlk) ratio (ρ). The results obtained demonstrated that rates of substrate uptake were correlated with concentration of biodegradable COD, through an equation of the Michaelis–Menten type. The kinetic equation obtained was used to simulate the anaerobic digestion process of this residue and to obtain the theoretical COD degradation rates in the reactor. The small deviations obtained (equal to or lower than 10%) between values calculated through the model and experimental values suggest that the proposed model predicts the behaviour of the reactor accurately. Copyright © 2007 Society of Chemical Industry     

Multi‐phase electro‐chemical catalytic oxidation of wastewater

The removal of organic pollutants from synthetic wash wastewater by a combined multi‐phase electro‐catalytic oxidation method was evaluated using porous graphite as anode and cathode, and CuO–Co₂O₃–PO₄^3? modified kaolin as catalyst. The synergic effect on COD removal was studied when integrating the electro‐chemical reactor with the effective modified kaolin in a single undivided cell; the results showed that higher COD removal efficiency was obtained than those obtained using the individual processes. Under optimal conditions of pH 3, 30 mA cm^?2 current density, very effective reduction of organic pollutants was achieved with this combined electro‐chemical method. High removal efficiency (90%) of the chemical oxygen demand (COD) was obtained in 60 min in the treatment of simulated wash wastewater (anionic surfactant, sodium dodecyl benzene sulfonate [DBS]). This method was also applied to treat wastewater form paper‐making and resulted in a COD reduction of 84%. Based on the investigation, a possible mechanism of this combined electro‐chemical process was proposed. The pollutants in wastewater could be decreased by the high reactive OH? that were produced via the decomposition of electro‐generated H₂O₂ activated by the synergic effect of electro‐field and catalyst. The results indicate that the multi‐phase catalytic electro‐chemical oxidation process is a promising technique for wastewater treatment. Copyright © 2006 Society of Chemical Industry     

A high‐efficient rotating disk photoelectrocatalytic (PEC) reactor with macro light harvesting pyramid‐surface electrode

A series of pyramid‐surface TiO₂/Ti electrodes were proposed, fabricated, and used in a rotating disk photoelectrocatalytic (PEC) reactor to treat rhodamine B (RB) solution. Compared with conventional planar electrode, pyramid‐surface electrode exhibited much lower light reflectivity, larger photocurrent, and better treatment efficiency. For samples containing 20 to 150 mg L^?1 RB, 100– 98% color removal, and 87–30% COD removal were obtained in 150 min using 1/3 (h/w) pyramid‐surface electrode, much higher than 98–77% and 48–9% obtained by a conventional planer electrode. The excellent treatment performance attributed to two major reasons: (a) enhanced light harvest resulted from multiple reflections of irradiation light on the pyramid‐surface, and (b) enlarged electrode surface area enabling the electrode to carry more TiO₂ catalyst and pollutants for treatment. Experimental results also showed that the pyramid‐surface electrode consumed less power and exhibited superior performance when treating high concentration wastewater. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2448–2455, 2012     

Performance of a ZVI‐UASB reactor for azo dye wastewater treatment

BACKGROUND: Zero valent iron (ZVI) is expected to be helpful for creating an enhanced anaerobic environment that might improve the performance of the anaerobic process. Based on this idea, a ZVI packed upflow anaerobic sludge blanket reactor (ZVI‐UASB) was developed to enhance azo dye wastewater treatment. RESULTS: The ZVI‐UASB reactor was less influenced by a decrease in the operational temperature from 35 °C to 25 °C than a reference UASB reactor that did not contain ZVI. In addition, chemical oxygen demand (COD) and color removal efficiencies of the ZVI‐UASB reactor at an HRT of 12 h exceeded those of the reference reactor at an HRT of 24 h. The hydraulic circulation in the ZVI bed enhanced the function of ZVI so that it improved the COD and color removal efficiencies. Moreover, fluorescence in situ hybridization experiments revealed that the abundance of Archaea in the sludge of the ZVI bed was significantly higher than that at the reactor bottom, which made the reactor capable of greater COD removal under low temperature and short HRT conditions. CONCLUSION: This ZVI‐UASB reactor could adapt well to changes in the operational conditions during wastewater treatment. Copyright © 2010 Society of Chemical Industry     

Two‐phase anaerobic treatment system for fat‐containing wastewater

This study was conducted to investigate the feasibility of a two‐phase anaerobic treatment system for fat‐containing wastewater. The two‐phase system was composed of a continuously stirred tank reactor for acidogenesis and an upflow anaerobic sludge blanket (UASB) reactor for methanogenesis. Its performance was compared with a conventional single‐phase system of a UASB reactor treating synthetic wastewater containing major long‐chain fatty acids (LCFAs). LCFAs did not cause any significant problem up to the LCFA mixture loading rate of 1.21 kg LCFA‐COD m^?3 day^?1 (3500 mg LCFA‐COD dm^?3) in both systems. However, the efficiency of the single‐phase system deteriorated at loading rates above 1.38 kg LCFA‐COD m^?3 day^?1 (4000 mg LCFA‐COD dm^?3), while that of the two‐phase system was still satisfactory. More than 19.2% of LCFAs were degraded and 11.5% of unsaturated LCFAs were saturated in the acidogenesis of the two‐phase system, which led to the enhanced specific methane production rate and the reduced scum layer of the subsequent UASB reactor. Copyright © 2003 Society of Chemical Industry     

Effects of cationic polymer on start‐up and granulation in upflow anaerobic sludge blanket reactors

The upflow anaerobic sludge blanket (UASB) has been used successfully to treat a variety of industrial wastewaters. It offers a high degree of organics removal, low sludge production and low energy consumption, along with energy production in the form of biogas. However, two major drawbacks are its long start‐up period and deficiency of active biogranules for proper functioning of the process. In this study, the influence of a coagulant polymer on start‐up, sludge granulation and the associated reactor performance was evaluated in four laboratory‐scale UASB reactors. A control reactor (R1) was operated without added polymer, while the other three reactors, designated R2, R3 and R4, were operated with polymer concentrations of 5 mg dm^?3, 10 mg dm^?3 and 20 mg dm^?3, respectively. Adding the polymer at a concentration of 20 mg dm^?3 markedly reduced the start‐up time. The time required to reach stable treatment at an organic loading rate (OLR) of 4.8 g COD dm^?3 d^?1 was reduced by more than 36% (R4) as compared with both R1 and R3, and by 46% as compared with R2. R4 was able to handle an OLR of 16 g COD dm^?3 d^?1 after 93 days of operation, while R1, R2 and R3 achieved the same loading rate only after 116, 116 and 109 days respectively. Compared with the control reactor, the start‐up time of R4 was shortened by about 20% at this OLR. Granule characterization indicated that the granules developed in R4 with 20 mg dm^?3 polymer exhibited the best settleability and methanogenic activity at all OLRs. The organic loading capacities of the reactors were also increased by the addition of polymer. The maximum organic loading of the control reactor (R1) without added polymer was 19.2 g COD dm^?3 d^?1, while the three polymer‐assisted reactors attained a marked increase in organic loading of 25.6 g COD dm^?3 d^?1. Adding the cationic polymer could result in shortening of start‐up time and enhancement of granulation, which may in turn lead to improvement in the efficiency of organics removal and loading capacity of the UASB system. Copyright © 2004 Society of Chemical Industry     

Treatment of high‐fat‐containing dairy wastewater in a sequential UASBR system: influence of recycle

BACKGROUND: Raw cheese whey originating from white cheese production results in a strong and complex wastewater excessively rich in organic matter (chemical oxygen demand, COD = 28–65 g L^?1), fatty matter (14–24.5 g L^?1) and acidity (3.9–6.1 g L^?1). It was treated in a three‐stage configuration consisting of a pre‐acidification (PA) tank and sequential upflow anaerobic sludge bed reactors (UASBRs) at 2.8–7 g COD L^?1 day^?1 organic loading rates, during which the effects of effluent recycling at low rates and promoted SRB activity were investigated. Acidification, volatile fatty acids (VFA), COD and fatty matter removal and volatile solids were monitored throughout the system during the study. RESULTS: Recycling of the effluent promoted VFA and COD removal as well as pH stability in both stages of the UASBRs and the effluent where high alkalinity levels were recovered reducing alkali requirement to 0.05 g OH g^?1 COD_applied. Higher removal rates of 71–100 and 50–92% for VFA and COD were obtained by use of recycling. Fatty matter was removed at 63–89% throughout the study. Volatile solids build‐up was significant in the inlet zones of the UASBRs. CONCLUSIONS: The system produced efficient acidification in the PA tank, balanced pH levels and an effluent high in alkalinity and BOD/COD ratio. Efficient VFA removal and solids immobilization was obtained in both stages up to the highest loading rate. Recycling improved the system performance under high fatty matter loading conditions. A major advantage of the sequential system was that the second stage UASBR compensated for reduced performance in the first stage. Copyright © 2010 Society of Chemical Industry     

Combined ozone pretreatment and biological processes for removal of colored and biorefractory compounds in wastewater from molasses fermentation industries

BACKGROUND: The use of ozone combined with biological treatment was investigated for molasses fermentation wastewater containing highly concentrated, brown and biorefractory compounds. These persistent compounds, known as melanoidins, generate disposal issues: in the environment, the color is problematic for aquatic life; and in municipal wastewater treatment plants, the molecules are biorefractory. RESULTS: This paper aims to evaluate the impact of ozone pretreatment, applied in the range 0.1 to 1 g g^?1 consumed ozone doses, on both macroscopic physico‐chemical parameters such as chemical oxygen demand (COD), total organic carbon (TOC), color and UV absorbance, and batch aerobic biodegradability. Then, performances of ozone pretreatment are assessed in terms of biodegradability improvement in batch and semi‐continuous anaerobic processes and, also, in semi‐continuous denitrification as a potential carbon source. Ozonation applied at the ozone dose of 0.5 g O₃ g^?1 COD led to an increase in biodegradability in all bioreactors. On average, the pretreatment resulted in an increased biodegradable fraction from zero to 33% without noticeable toxicity on biomass. This ozone dose also achieved 45% nitrogen removal by biological denitrification. CONCLUSION: Ozone pretreatment is a suitable technique for the biodegradability improvement of molasses fermentation wastewater, in aerobic, anaerobic and anoxic conditions. The pretreatment should be optimized in order to maximize the subsequent biodegradability. Copyright © 2010 Society of Chemical Industry     

Biological treatment of saline wastewaters from marine‐products processing factories by a fixed‐bed reactor

Wastewaters generated by a factory processing marine products are characterized by high concentrations of organic compounds and salt constituents (>30 g dm^?3). Biological treatment of these saline wastewaters in conventional systems usually results in low chemical oxygen demand (COD) removal efficiency, because of the plasmolysis of the organisms. In order to overcome this problem a specific flora was adapted to the wastewater from the fish‐processing industry by a gradual increase in salt concentrations. Biological treatment of this effluent was then studied in a continuous fixed biofilm reactor. Experiments were conducted at different organic loading rates (OLR), varying from 250 to 1000 mg COD dm^?3 day^?1. Under low OLR (250 mg COD dm^?3 day^?1), COD and total organic carbon (TOC) removal efficiencies were 92.5 and 95.4%, respectively. Thereafter, fluctuations in COD and TOC were observed during the experiment, provoked by the progressive increase of OLR and the nature of the wastewater introduced. High COD (87%) and TOC (99%) removal efficiencies were obtained at 1000 mg COD dm^?3 day^?1. © 2002 Society of Chemical Industry     

Degradation of 1‐amino‐4‐bromoanthraquinone‐2‐sulfonic acid using combined airlift bioreactor and TiO2‐photocatalytic ozonation

BACKGROUND: Traditional treatment systems failed to achieve efficient degradation of anthraquinone dye intermediates at high loading. Thus, an airlift internal loop reactor (AILR) in combination with the TiO₂‐photocatalytic ozonation (TiO₂/UV/O₃) process was investigated for the degradaton of 1‐amino‐ 4‐bromoanthraquinone‐2‐ sulfonic acid (ABAS). RESULTS: The AILR using Sphingomonas xenophaga as inoculum and granular activated carbon (GAC) as biocarrier, could run steadily for 4 months at 1000 mg L^?1 of the influent ABAS. The efficiencies of ABAS decolorization and chemical oxygen demand (COD) removal in AILR reached about 90% and 50% in 12 h, respectively. However, when the influent ABAS concentration was further increased, a yellow intermediate with maximum absorbance at 447 nm appeared in AILR, resulting in the decrease of the decolorization and COD removal efficiencies. Advanced treatment of AILR effluent indicated that TiO₂/UV/O₃ process more significantly improved the mineralization rate of ABAS bio‐decolorization products with over 90% TOC removal efficiency, compared with O₃, TiO₂/UV and UV/O₃ processes. Furthermore, the release efficiencies of Br^? and SO₄^2? could reach 84.5% and 80.2% during TiO₂/UV/O₃ treatment, respectively, when 91.5% TOC removal was achieved in 2 h. CONCLUSION: The combination of AILR and TiO₂/UV/O₃ was an economic and efficient system for the treatment of ABAS wastewater. © 2012 Society of Chemical Industry     

Investigation of municipal and olive mill wastewater co‐treatment in activated sludge–powdered activated carbon (AS‐PAC) systems

BACKGROUND: The purpose of this study was to investigate the co‐treatment of olive‐mill wastewater (OMW) and municipal wastewater in activated sludge systems operating in the absence and presence of different adsorbent materials and to study the role of sorption and biodegradation in total phenols removal. RESULTS: Batch experiments were initially conducted to investigate total phenols' adsorption capacity on activated sludge (AS), olive pomace (OP) and powdered activated carbon (PAC). According to the results, PAC presented the best adsorption capacity. Three sequencing batch reactors (SBRs) were also operated, treating municipal wastewater and different amounts of OMW. The first SBR contained AS (AS‐System), the second AS and OP (AS‐OP System) and the third AS and PAC (AS‐PAC System). All SBRs operated sufficiently in the presence of 1% v/v OMW, achieving mean COD and total phenols removal efficiency higher than 86% and 85%, respectively, and satisfactory settling capacity. Increase of OMW concentration to 5% v/v affected the performance of SBRs, resulting in mean COD removal efficiencies that ranged between 61% (AS‐OP System) and 80% (AS‐PAC System). CONCLUSION: Among the SBRs used, the AS‐PAC System operated with highest performance in the presence of 1 and 2.5% v/v OMW, and showed better stability in the presence of 5% v/v OMW. Calculation of total phenols mass flux revealed that biodegradation was the principal mechanism of their removal. The highest values of mean biotransformation rates were calculated for the AS‐PAC System and ranged between 2.0 and 40.6 d^?1 for different experimental phases. Copyright © 2012 Society of Chemical Industry     

The influence of influent distribution and blood content of slaughterhouse wastewater on the performance of an anaerobic fixed‐film reactor

This paper evaluates the performance of a laboratory‐scale anaerobic fixed‐film reactor (AFFR) with arranged media treating slaughterhouse wastewater. The reactor was operated at 20 °C, its organic loading rate was increased from 1.8 to 9.2 kg COD m^?3 d^?1, and it had a short hydraulic residence time (5–9 h). The influence of wastewater concentrations on its performance was studied by artificially increasing the blood content of the wastewater. The efficiency of the removal of organic matter decreased from 70% to 54% as the superficial velocity increased from 0.12 to 0.97 m h^?1, due mainly to distribution defects, as had been confirmed experimentally by tracer tests. The kinetics of the anaerobic processes was limited by substrate availability, even at high COD concentrations (between 700 and 1100 mg dm^?3) due to a high content of slowly biodegradable and inert compounds present in the wastewater from the slaughterhouse. It was observed that a large amount of the organic matter had accumulated inside the reactor instead of being removed by methanogenic digestion. Furthermore, the fraction of organic matter held inside the reactor varied significantly in relation to the blood content of the wastewater. Copyright © 2005 Society of Chemical Industry     

Treatment of paper and pulp wastewater and removal of odorous compounds by a Fenton‐like process at the pilot scale

A Fenton‐like process, involving oxidation and coagulation, was evaluated for the removal of odorous compounds and treatment of a pulp and paper wastewater. The main parameters that govern the complex reactive system [pH and Fe(III) and hydrogen peroxide concentrations] were studied. Concentrations of Fe(III) between 100 and 1000 mg L^?1 and of H₂O₂ between 0 and 2000 mg L^?1 were chosen. The main mechanism for color removal was coagulation. The maximum COD, color and aromatic compound removals were 75, 98 and 95%, respectively, under optimal operating conditions ([Fe(III)] = 400 mg L^?1; [H₂O₂] = 500–1000 mg L^?1; pH = 2.5; followed by coagulation at pH 5.0). The biodegradability of the wastewater treated increased from 0.4 to 0.7 under optimal conditions and no residual hydrogen peroxide was found after treatment. However, partially or non‐oxidized compounds present in the treated wastewater presented higher acute toxicity to Artemia salina than the untreated wastewater. Based on the optimum conditions, pilot‐scale experiments were conducted and revealed a high efficiency in relation to the mineralization of organic compounds. Terpenes [(1S)‐α‐pinene, β‐pinene, (1R)‐α‐pinene and limonene] were identified in the wastewater and were completely eliminated by the Fenton‐like treatment. Copyright © 2006 Society of Chemical Industry     

BDD anodic oxidation as tertiary wastewater treatment for the removal of emerging micro‐pollutants,pathogens and organic matter

This work reports for the first time the removal of 17α‐ethynylestradiol (EE2), a synthetic estrogen hormone, from secondary treated effluents by electrochemical oxidation. Experiments were conducted in a single compartment reactor comprising a boron‐doped diamond (BDD) anode and a zirconium cathode. EE2, in the range 100–800 µg L^?1, was spiked in the post‐chlorination effluent of a municipal treatment plant and oxidized at 0.9–2.6 mA cm^?2 current density. Complete degradation of 100 µg L^?1 EE2 was achieved in 7 min at 2.1 mA cm^?2 and inherent conditions, while the addition of 0.1 mol L^?1 NaCl achieved removal in just a few seconds. The process was then tested in the pre‐chlorination effluent at 2.1 mA cm^?2 and inherent conditions; complete E. coli killing and EE2 removal occurred in just 1.5 and 3.5 min, respectively, while overall estrogenicity (assessed by the YES assay) and residual organic matter (in terms of chemical oxygen demand (COD)) decreased by 50% and 85% after 30 min, respectively. These results clearly show the potential of BBD electrochemical oxidation to serve as an efficient tertiary wastewater treatment. Copyright © 2011 Society of Chemical Industry     

Pilot‐scale demonstration of pre‐fermentation for enhancement of food‐processing wastewater biodegradability

A pilot‐scale anaerobic/aerobic ultrafiltration system was tested to treat high‐strength tomato‐processing wastewater, to achieve stringent dry‐ditch discharge criteria of soluble biochemical oxygen demand (SBOD) <10 mg dm^?3, total suspended solids <10 mg dm^?3, ammonia nitrogen <3 mg dm^?3 and soluble phosphorus <0.5 mg dm^?3. The anaerobic/aerobic system achieved 99.4% SBOD removal, 91.9% NH₃ N removal and 100% phosphorus removal at an overall hydraulic retention time of 1.5 days and solids retention time of 5 days during the tomato canning season. Respirometric studies confirmed that the pretreatment of tomato‐processing wastewater in the anaerobic reactor increased the readily biodegradable fraction, improved kinetics, and eliminated nutrient deficiency problem. Copyright © 2006 Society of Chemical Industry     

2,4,6‐Trichlorophenol and phenol removal in methanogenic and partially‐aerated methanogenic conditions in a fluidized bed bioreactor

A fluidized bed bioreactor (FBBR) was operated for more than 575 days to remove 2,4,6‐trichlorophenol (TCP) and phenol (Phe) from a synthetic toxic wastewater containing 80 mg L^?1 of TCP and 20 mg L^?1 of Phe under two regimes: Methanogenic (M) and Partially‐Aerated Methanogenic (PAM). The mesophilic, laboratory‐scale FBBR consisted of a glass column (3 L capacity) loaded with 1 L of 1 mm diameter granular activated carbon colonized by an anaerobic consortium. Sucrose (1 g COD L^?1) was used as co‐substrate in the two conditions. The hydraulic residence time was kept constant at 1 day. Both conditions showed similar TCP and Phe removal (99.9 + %); nevertheless, in the Methanogenic regime, the accumulation of 4‐chlorophenol (4CP) up to 16 mg L^?1 and phenol up to 4 mg L^?1 was observed, whereas in PAM conditions 4CP and other intermediates were not detected. The specific methanogenic activity of biomass decreased from 1.01 ± 0.14 in M conditions to 0.19 ± 0.06 mmolCH₄ h^?1 gTKN^?1 in PAM conditions whereas the specific oxygen uptake rate increased from 0.039 ± 0.008 in M conditions to 0.054 ± 0.012 mmolO₂ h^?1 gTKN^?1, which suggested the co‐existence of both methanogenic archaea and aerobic bacteria in the undefined consortium. The advantage of the PAM condition over the M regime is that it provides for the thorough removal of less‐substituted chlorophenols produced by the reductive dehalogenation of TCP rather than the removal of the parent compound itself. Copyright © 2005 Society of Chemical Industry     

Treatment of settled piggery waste by a down‐flow anaerobic fixed bed reactor

A study of the effect of organic volumetric loading rate (B_V) on the performance of a down‐flow anaerobic fixed bed reactor (DFAFBR) treating settled piggery waste was carried out at a range of between 1.1 and 6.8 g COD dm^?3 d^?1. The reactor operated at good removal efficiencies and stability under the operational conditions studied. Logarithmic empirical equations described adequately the removal efficiency for different parameters studied (COD, SCOD, BOD, TS, VS, TSS, VSS and phosphorous). Although process stability was affected by the increase of B_V, process failure was not observed. A logarithmic relationship was found to describe the influence of B_V on the TVFA/alkalinity ratio (p). A linear correlation was found between the effluent substrate concentration and the values of p and between p and the CO₂/CH₄ ratio in the biogas. The effect of the hydraulic volumetric loading rate (H_V) on the flow pattern of the reactor was evaluated. Dispersion number (D_n) was in the range of 0.17–0.37 for the maximum and minimum values of H_V studied, respectively. The ratio between the real and theoretical HRT increased as the H_V decreased. These results demonstrate that axial dispersion increased as the H_V and the Reynolds number decreased. Due to the hydraulic behaviour of the reactor, the kinetic model developed by Lawrence and McCarty was used for describing the experimental results obtained. Maximum specific substrate removal rate (K), specific organic loading rate constant (K_L), microbial decay coefficient (K_d), microbial yield coefficient (Y), maximum microbial growth rate (U_M) and saturation constant (K_S) were found to be: 3.1 (g COD g VSS^?1 d^?1), 3.0 (g COD g VSS^?1 d^?1), 0.062 (d^?1), 0.15 (g VSS g COD removed^?1), 0.39 (d^?1) and 2.6 (g SCOD dm^?3), respectively. Copyright © 2004 Society of Chemical Industry     

Preparation of O‐carboxymethyl‐N‐trimethyl chitosan chloride and flocculation of the wastewater in sugar refinery

A novel water soluble amphiphilic O‐ carboxymethyl‐N‐trimethyl Chitosan chloride (CMTMC) was synthesized. The structure of this material was characterized by Fourier transform infrared (FTIR) spectroscopy, ¹³C nuclear magnetic resonance (¹³C‐NMR) spectroscopy and X‐ray diffraction (XRD) techniques. The results showed that CMTMC had been successfully prepared. To determine the flocculation performance of the synthesized amphiphilic polymer, a comparison was made among Chitosan (CS), N‐trimethyl chitosan chloride (TMC), O‐carboxymethyl chitosan (CMC), and CMTMC on the turbidity and COD removal efficiency of 1% (v/v) wastewater in sugar refinery suspensions at pH 5.0, 7.0 and 9.0 at a dosage range of 0–8 mg/L. The results showed that the water soluble amphiphilic polymer CMTMC, which contains longer polymer anion and polymer cation, had the best performance not only in turbidity removal but also in COD removal on sugar refinery wastewater. The using of CMTMC as a flocculant to treat wastewater in sugar refinery was actually more effective than CS, CMC, and TMC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010