Simultaneous Removal of Carbon and Nitrogen from Swine Wastewater Using an Immobilized-Cell Reactor

A single-stage phosphorylated polyvinyl alcohol immobilized-cell reactor with three operation modes was employed to investigate the efficiency of simultaneous carbon/nitrogen removal from raw swine wastewater. In continuous aeration mode, the removal efficiency of chemical oxygen demand (COD) and total nitrogen (T-N) exceeded 70 and 8%, respectively, at hydraulic retention time of 10?days. In intermittent aeration (IA) mode, the removal efficiency of COD and T-N was more than 85 and 46%, respectively, when the reactor was set at 50% aeration duration to cycle time to operate at three aerobic-anoxic cycles per day. When oxidation-reduction-potential control was adopted to control the duration of the anoxic period in the real-time controlled (RTC) IA mode for a 4?h aeration period, the total cycle time was reduced by about 20% with a slight increase in removal efficiency of COD (87%) and T-N (47%). The system with no extra chambers required is efficient in simultaneous carbon/nitrogen removal.     

Simultaneous Nitrogen and Phosphorus Removal from High-Strength Industrial Wastewater Using Aerobic Granular Sludge

Aerobic granular sludge technology was applied to the simultaneous nitrogen and phosphorus removal from livestock wastewater that contains high concentrations of nitrogen and phosphorus (TN: 650?mg/L; TP: 125?mg/L). A lab-scale sequencing batch reactor was operated in an alternating anaerobic/oxic/anoxic denitrification mode. Granular sludge was first formed using synthetic wastewater. When livestock wastewater was diluted with tap water, the shape and settleability of aerobic granular sludge were maintained even though livestock wastewater contained suspended solids. Simultaneous nitrification, denitrification, and phosphate uptake were observed under an aerobic condition. However, when nondiluted livestock wastewater was used, the diameter of granular sludge and the denitrification efficiency under an oxic condition decreased. When the concentrations of nitrogen and phosphorus in wastewater increased, hydraulic retention time (HRT) increased resulting in a decrease in selection pressure for granular sludge. Therefore, the sustainment of granular sludge was difficult in livestock wastewater treatment. However, by applying a new excess sludge discharge method based on Stokes’ law, the shape of granular sludge was maintained in spite of the long HRT (7.5?days). To select large granular sludge particles, excess sludge was discharged from the upper part of settled sludge because small particles localized there after settling. Finally, excellent nitrogen and phosphorus removal was accomplished in practical livestock wastewater treatment. The effluent concentrations of NH4–N, NOx–N, and PO4–P were <0.1, 1.4, and 1.2?mg/L, respectively.     

Toward Polyhydroxyalkanoate Production Concurrent with Municipal Wastewater Treatment in a Sequencing Batch Reactor System

Bacteria can synthesize cytoplasmic granules known as polyhydroxyalkanoates (PHAs), which are carbon and energy storage reserves, from organic carbon when subject to stressful environmental conditions. PHAs are also biodegradable thermoplastics with many potential commercial applications. The purpose of the research reported herein was to evaluate the feasibility of integrating PHA production within a municipal wastewater treatment (WWT) configured as a sequencing batch reactor (SBR). Four bench-scale WWT SBRs were tested at decreasing organic loading rates to assess the potential to enrich for microbes capable of feast/famine PHA synthesis. For each treatment SBR, sidestream batch reactors receiving higher quantities of primary solids fermenter liquor were operated to produce PHA. Results from this study demonstrate that a treatment SBR supplied moderate strength wastewater can enrich for the target microorganisms, with PHA yields of 0.23–0.31-mg PHA per mg chemical oxygen demand, and produce high quality effluent. In sidestream batch reactors, microorganisms that fed excess quantities of substrate can rapidly synthesize significant quantities of PHA. Based on the results of this study, we estimate that a 1 million gallon per day SBR WWT-PHA production system could generate 11–36 t (12–40 t) of PHA annually.     

Combined Removal of Carbon and Nitrogen in an Integrated UASB-Jet Loop Reactor Bioreactor System

An innovative anaerobic–aerobic integrated bioreactor system consisting of an upflow anaerobic sludge blanket (UASB) and a jet loop reactor was developed to investigate the feasibility of combined removal of carbon and nitrogen for a low-strength wastewater at different hydraulic retention times (HRTs) and recycle ratios. Total chemical oxygen demand (COD) removal of the integrated system increased from 87 to 92%, at a combined system HRT of 44?h, when the recycle ratio was increased from 100 to 400%, respectively. Denitrification efficiency of the integrated system increased from 49 to 86%, at all HRTs, when the recycle ratio was increased from 100 to 400%. The integrated system, on average, achieved more than 78% of total nitrogen at all HRTs. Nitrogen content of the biogas produced from the UASB reactor increased with increase in recycle ratios while the methane content exhibited a reverse trend, irrespective of the HRTs. Sludge volume index of the UASB reactor increased from 15?to?42?mL/g total suspended solids at the end of the study. Specific methanogenic activity of the granular sludge decreased from 1.3 to 0.8 g CH4–COD/g volatile suspended solids per day at the end of the study. Nitrogen and COD mass balance of the integrated system indicated that a substantial amount of influent nitrogen and COD was lost in the effluent as dissolved form.     

Simultaneous Organic and Nutrient Removal in a Naturally Ventilated Biotower Treating Presettled Municipal Wastewater

The performance of a down-flow hanging sponge (DHS) system was continuously evaluated for 1 year for enhancement of organic matter and nutrient removal in the treatment of presettled municipal wastewater. A pilot-scale DHS (24 L) was installed at a wastewater-treatment site and operated at an ambient temperature of 25°C. This paper reports on the results of a long-term monitoring of the system. The DHS system was operated at three different hydraulic retention times (HRTs), i.e., 6, 4, and 2 h. The available results showed that increasing the HRT significantly improved the removal of chemical oxygen demand (COD) fractions. The removal efficiencies of COD were 89, 80, and 56% at HRTs of 6, 4, and 2 h, respectively. Also, ammonia (NH4–N) concentration significantly decreased by increasing the HRT. Ammonia removal percentages of 99, 90, and 72% were achieved when the DHS system was operated at HRTs of 6, 4, and 2 h, respectively, but decreasing HRT exerted a slightly negative effect on the removal of total phosphorous. Scanning electron microscopy observation revealed no clogging of the sponge pores after 12 months of continuous operation. Accordingly, the results suggested that the proposed system may be a competitive solution for municipal wastewater treatment under variable conditions.     

Algae Grown on Dairy and Municipal Wastewater for Simultaneous Nutrient Removal and Lipid Production for Biofuel Feedstock

Algae grown on wastewater media are a potential source of low-cost lipids for production of liquid biofuels. This study investigated lipid productivity and nutrient removal by green algae grown during treatment of dairy farm and municipal wastewaters supplemented with CO2. Dairy wastewater was treated outdoors in bench-scale batch cultures. The lipid content of the volatile solids peaked at Day 6, during exponential growth, and declined thereafter. Peak lipid content ranged from 14–29%, depending on wastewater concentration. Maximum lipid productivity also peaked at Day 6 of batch growth, with a volumetric productivity of 17 mg/day/L of reactor and an areal productivity of 2.8?g/m2/day, which would be equivalent to 11,000 L/ha/year (1,200 gal/acre/year) if sustained year round. After 12 days, ammonium and orthophosphate removals were 96 and >99%, respectively. Municipal wastewater was treated in semicontinuous indoor cultures with 2–4 day hydraulic residence times (HRTs). Maximum lipid productivity for the municipal wastewater was 24 mg/day/L, observed in the 3-day HRT cultures. Over 99% removal of ammonium and orthophosphate was achieved. The results from both types of wastewater suggest that CO2-supplemented algae cultures can simultaneously remove dissolved nitrogen and phosphorus to low levels while generating a feedstock potentially useful for liquid biofuels production.     

Use of a Sequencing Batch Reactor for Nitrogen and Phosphorus Removal from Municipal Wastewater

In this study, a suspended growth sequencing batch reactor (SBR) and an attached cum suspended growth SBR were used to investigate the performance characteristics of nitrogen and phosphorus (NP) removal from municipal sewage. The effects of three controlling factors, namely batch loading rate, feed pattern (initial feed or step feed), and mixing/aeration ratio, on NP removal were investigated under nine different experimental conditions. Owing to a large number of possible combinations among the controlling factors and different experimental conditions, it is very difficult to enumerate all the available combinations experimentally. In view of this, the Taguchi method, a cost-effective technique for design of experiments, was exploited for estimating the optimal operating condition. This study also evaluated the difference between the suspended growth SBR and the attached cum suspended growth SBR. The total nitrogen (TN), total phosphorus (TP), total biochemical oxygen demand (TBOD)5, and suspended solids (SS) removal efficiencies were 90.2, 83.9, 98.6, and 93.0%, respectively, for the suspended growth SBR. The corresponding values for the attached cum suspended growth SBR were 92.6, 82.1, 98.3, and 93.1%, respectively. It was observed that the batch loading rate influenced the efficiencies in terms of TN removal. It was also noted that step feed and mixing/aeration ratio had significant impact on TP removal performance. The optimal operating condition for the suspended growth SBR system in terms of batch loading rate, feed pattern, and mixing/aeration ratio were 0.170?mgBOD5/mgMLVSS?d, initial feed, and 1-to-1, respectively. The associated TN, TP, TBOD5, and SS removal efficiencies for the suspended growth SBR were 93.8, 98.2, 99.6, and 98.5%, respectively. The corresponding results for the attached cum suspended growth SBR system were 0.170?mgBOD5/mgMLVSS?d, initial feed, and 3-to-1, respectively. Similarly, the corresponding removal efficiencies for the attached cum suspended growth SBR were 94.7, 97.8, 99.3, and 98.8%, respectively.     

Combined System for Biological Removal of Nitrogen and Carbon from a Fish Cannery Wastewater

A combined system composed of three sequentially arranged reactors, anaerobic-anoxic-aerobic reactors, was used to treat the wastewater generated in the tuna cookers of a fish canning factory. These wastewaters are characterized by high chemical oxygen demand (COD) and nitrogen concentrations. The anaerobic process was performed in an upflow anaerobic sludge blanket reactor operated in two steps. During Step I different influent COD concentrations were applied and organic loading rates (OLRs) up to 4 g COD/(L?d) were achieved. During Step II hydraulic retention time (HRT) was varied from 0.5 to 0.8 days while COD concentration in the influent was constant at 6 g COD/L. The OLRs treated were up to 15 g COD/(L?d). When HRTs longer than 0.8 days were used, COD removal percentages of 60% were obtained and these values decreased to 40% for a HRT of 0.5 days. The denitrification process carried out in an upflow anoxic filter was clearly influenced by the amount of carbon source supplied. When available carbon was present, the necessary COD/N ratio for complete denitrification was around 4 and denitrification percentages of 80% were obtained. The nitrification process was successful and was almost unaffected by the presence of organic carbon (0.2–0.8 g TOC/L), with ammonia removal percentages of 100%. Three recycling ratios (R/F) between the denitrification and nitrification reactors were applied at 1, 2, and 2.5. The overall balance of the combined system indicated that COD and N removal percentages of 90% and up to 60%, respectively, were achieved when the R/F ratio was between 2 and 2.5.     

Influence of COD/N Ratios on Simultaneous Removal of C and N Compounds in Biological Wastewater Treatment in Sequencing Fed-Batch Reactor and Kinetic Analysis

The impact of chemical oxygen demand/nitrogen (COD/N) values of feed wastewater on COD and nitrogen removal and biomass growth in a sequencing fed-batch reactor (SFBR) operation was investigated. The multiple microbial reactions involved in the simultaneous removal process of carbonaceous and nitrogenous components in the SFBR system were analyzed using a set of kinetics mathematical model. The results indicate that COD/N ratios strongly influence COD and total nitrogen removal efficiency. The COD removal efficiency per gram microorganism changed from 64.3 to 78.1% at COD/N = 11.9–2.5. The total nitrogen removal efficiency changed from 10.3 to 34.2% at COD/N = 2.5–11.9. However, variable COD/N ratios of feed wastewater are not marked for biomass growth rate.     

Precipitation Removal of Fluoride from Semiconductor Wastewater

Chemical precipitation method utilizing calcium salts has been extensively used to treat fluoride-containing wastewater from semiconductor manufacturers. The major objective of this study was to investigate coagulation-flocculation of calcium fluoride precipitates (CaF2). Residual fluoride concentration of lower than 15?mg/L, the effluent standard, was found when molar ratio of calcium to fluoride, [Ca2+/F?], was 0.5 and pH ranged from 6.5 to 8.5. The fine precipitates of CaF2 were further flocculated by polyaluminum chloride (PAC) and anionic polyelectrolyte, polyacrylic acid (PAA) with different molecular weight, to facilitate better solid-liquid separation. Experimental results indicated that both PAC and PAA with low to medium molecular weight could remove CaF2 precipitates effectively. Satisfactory removal efficiency was achieved at lower dosage when PAC and PAA were used in combination. Recycling of CaF2 precipitates or CaF2 sludge did not enhance removal of fluoride or CaF2 precipitates. Reaction mechanisms were discussed based on zeta potential and particle size distribution.     

Single-Submerged Attached Growth Bioreactor for Simultaneous Removal of Organics and Nitrogen

The use of a single-unit, single-zone submerged attached growth bioreactor (SAGB) for the combined removal of carbonaceous organics and nitrogen from a municipal wastewater was demonstrated. A nitrification efficiency of 97% was achieved at a total organic loading of 3.47?kg?bCOD/m3?day. The total nitrogen loading varied from 0.2?to?0.3?kg?N/m3?day and resulted in effluent total nitrogen concentrations ranging from 4.2?to?8.5?mg/L. Concurrent denitrification was achieved at rates ranging from 0.077?to0.29?kg?N/m3?day. This single-unit SAGB, by providing dual treatment capacities, represents a cost-effective option that is particularly attractive for facilities with limited space and budget for system upgrade.     

Wastewater Management in the 21st Century

A dialogue concerning potential future directions for the wastewater profession is initiated by identifying four principal challenges. The first is the perception by many (at least in the United States) that water pollution and water quality problems have largely been solved. Dramatic improvements during the 20th century (by the founders of our profession, not by us!) have eliminated many of the obvious public health and environmental issues associated with wastewater management. The second is population growth and the associated added stress on water resources. The third is the potential (at least perceived) conflict between providing improved water and wastewater service to the poor (especially in developing countries) and reducing the environmental impacts of our systems. The fourth is to determine whether we are wastewater managers, or more broadly water managers. These challenges can be addressed by adopting a broader, more holistic view of urban water management incorporating water supply, wastewater management, and storm water. A toolkit of existing and evolving technologies could be assembled and grouped into example systems. Improved methods for evaluating alternate urban water management systems based on sustainable development principles need to be developed. Achieving the vision of more sustainable urban water management systems requires that our professional organizations speak with one voice. Our profession must also reach out and engage a wide range of interests in defining and implementing dramatically improved solutions.     

Modeling of Cadmium Removal from Domestic Wastewater in Constructed Wetlands Using STELLA Simulation Program

A mathematical model was developed to simulate cadmium removal from wastewater in free water surface (FWS) and subsurface flow (SF) constructed wetlands using STELLA simulation program. The model simulated the accumulation of cadmium in soil (Cds), uptake by plants (Cdp), and residual concentration in effluent (Cdww_eff). The model was calibrated using one-half of the experimental data for the adjustment of the coefficients and the remaining data for model verification. The comparison of simulated and experimental values of Cds, Cdp, and Cdww_eff showed good agreement. The results indicated that the developed mathematical model could be useful for predicting the fate of cadmium when treating domestic effluents in constructed wetlands.     

Removal of Zn2+ from Electroplating Wastewater Using Modified Wood Sawdust and Sugarcane Bagasse

This paper describes the preparation of new adsorbents derived from sugarcane bagasse and wood sawdust (Manilkara sp.) to remove zinc (II) ions from electroplating wastewater. The first part deals with the chemical modification of sugarcane bagasse and wood sawdust, using succinic anhydride to introduce carboxylic acid functions into the material. The obtained materials (modified sugarcane bagasse MB2 and modified wood sawdust MS2) were then characterized by infrared spectroscopy (IR) and used in adsorption experiments. The adsorption experiments evaluates Zn2+ removal from aqueous single metal solution and real electroplating wastewater on both batch and continuous experiments using fixed-bed columns prepared in laboratorial scale with the obtained adsorbents. Adsorption isotherms were then developed using Langmuir model and the Thomas kinetic model. The calculated Zn2+ adsorption capacities were found to be 145?mg/g for MS2 and 125?mg/g for MB2 in single metal aqueous solution, whereas for the industrial wastewater these values were 61?mg/g for MS2 and 55?mg/g for MB2.     

Simultaneous Nitrogen and Phosphorus Removal Using a Double Sludge Switching Sequencing Batch Reactor

A new process using a sequencing batch reactor (SBR) and two smaller sludge hoppers is proposed for the simultaneous removal of phosphorus and nitrogen from wastewater. In the double sludge switching sequencing batch reactor, denitrifying phosphate accumulating bacteria (DPB) sludge and nitrification sludge are transferred to the SBR at different phases instead of flowing wastewater through different reactors. The process was operated with a cycle time of 10.5?h, consisting of DPB sludge filling phase (0.5?h), anaerobic phase I (2.0?h), settling and changing DPB sludge phase (0.5?h), anaerobic phase II (0.5?h), aerobic phase (4.0?h), settling and changing nitrifying sludge phase (0.5?h), and anoxic phase (3.0?h). Results of stable operation showed that the process was very efficient over a range of temperatures varied from 10?to?28°C. The average effluent concentrations and removal efficiencies were as follows: CODCr 28.0?mg/L, 92.1%; BOD5 7.0?mg/L, 95.1%; NH3–N 0.8?mg/L, 98.0%; TN 9.8?mg/L, 76.7%; and TP 0.5?mg/L, 92.3%.     

Cell Immobilized FOG-Trap System for Fat, Oil, and Grease Removal from Restaurant Wastewater

Cell immobilized lipase-producing bacteria on three different matrices were incorporated in a fat-, oil-, and grease (FOG) trap system for restaurant wastewater treatment. During a 16-day laboratory-scale experiment for the treatment of synthetic FOG wastewater containing soybean oil, no significant difference (two-tailed t test at 95% confidence interval) in the FOG removal between two systems was observed at FOG influent ≤ 1,000?mg/L. However, the typical trap showed lower FOG removal efficiency than the matrix-based system when the influent FOG concentration was increased to ≥ 5,000?mg/L. In addition, the matrix-based trap system was able to sustain a stable high FOG removal, with <100?mg/L effluent, even at 10,000 mg/L influent FOG. Based on FOG heights measured and mass balance calculations, 97.4 and 99.5% of the total FOG load for 16 days were removed in a typical trap and matrix-based system, respectively. About 93.6% of the removal in the matrix-based was accounted to biodegradation. The 30-day full-scale operations demonstrated a distinguishably better performance in the matrix-based system (92.7±9.06% of 1,044.8±537.27?mg FOG/L) than in the typical trap system (74.6±27.13% of 463.4±296.87?mg FOG/L) for the treatment of barbeque restaurant wastewater. Similarly, matrix-based system revealed higher chemical oxygen demand removal (85.9±11.99%) than the typical trap system (60.4±31.26%). Characterizations of the influent, emulsified, adsorbed and effluent FOG indicated that straight saturated fatty acids constituted the cause of clogging problems in the FOG-trap and piping system.     

Methodological Aspects of Using Blast Furnace Slag for Wastewater Phosphorus Removal

Blast furnace (BF) slag is a by-product of steel plants. The objective of this study was to evaluate experimental methods to determine the phosphorus sorption capacity of BF slag. The handling of BF slag, before usage and clogging were also considered, as well as estimating the phosphorus retention capacity. Agitation and pilot-scale experiments were performed using both wastewater and phosphate solutions. This investigation showed that sorption capacities derived by wastewater experiments were considerably lower compared to those by phosphate solutions. Fresh BF slag briefly exposed to rainfall had a higher phosphorus sorption than weathered BF slag, indicating the importance of handling the slag carefully before usage. The risk for leakage of sulfuric compounds is considerable, especially during the initial operation phase of BF slag filters. Locations of BF slag filter beds for wastewater treatment must be carefully chosen from an environmental point of view.     

Laccase-Catalyzed Removal of Phenol and Benzenediols from Wastewater

A two-step process for the removal of phenol and benzenediols, namely catechol, resorcinol, and hydroquinone, from buffered synthetic wastewater was investigated. The proposed process comprised laccase catalyzed conversion of these substrates using laccase from Trametes villosa followed by the removal of products generated using alum as coagulant. The effects of pH, laccase concentration, substrate concentration, and the presence of a hydrophilic polymer additive [polyethylene glycol (PEG)] to achieve ≥ 95% removal of the substrate in a 3-h reaction period at room temperature were determined. The parent compound, phenol, required the most enzyme, followed by resorcinol, catechol, and hydroquinone. PEG showed no effect on any of the substrate conversions. Substrate conversion and enzyme inactivation were monitored over the reaction period. As phenol and benzenediols might coexist in industrial effluents, enzymatic treatment of an equimolar mixture of these four substrates was examined. Except for hydroquinone, the proposed enzymatic treatment method is a viable alternative means to remove phenol and benzenediols from industrial wastewaters.     

Municipal Wastewater Treatment Using a UASB Coupled with Cross-Flow Membrane Filtration

A pilot scale up-flow anaerobic sludge blanket (UASB) coupled with cross-flow membrane filtration was used to treat low strength municipal wastewater in Singapore. The application of membrane filtration as a polishing unit of UASB effluent could produce better effluent quantity than conventional UASB. In this research, with gradually reducing hydraulic retention time from 10.0?to?5.5?h, membrane effluent was able to meet the more stringent effluent criterion over the whole experiment. Simultaneously, biogas yield increased from 61.8?to?120.7?mL/g CODremoved, in which methane percentages were also increased from 59.3 to 65.2%, respectively. Furthermore, the results of anaerobic membrane filtration showed that there were three different methods could effectively mitigate rapid membrane fouling and maintain trans-membrane pressure as low and stable as possible. These would reduce membrane cleaning frequency and prolong membrane life span.     

Changes in Polyhydroxy-Alkanoates (PHAs) during Enhanced Biological Phosphorus Removal with Dairy Industrial Wastewater

Using the industrial wastewater from a dairy plant, the performance of enhanced biological phosphorus removal (EBPR) with complex organic substances was evaluated. A laboratory-scale sequencing batch reactor (SBR) was operated and the organic loading rate in total chemical oxygen demand (tCOD) increased gradually from 200–600?g-tCOD?m?3?cycle?1 in three steps. As the organic loading increased, the food to microorganism ratio (F/M) increased from 0.16–0.27 (g-tCOD/g-MLVSS d). When it increased over 600?g-tCOD?m?3?cycle?1, the effluent phosphorus concentration fluctuated, showing an unstable EBPR activity. During the anaerobic condition, higher fraction of poly-3-hydroxyvalerate (PHV) was observed and the ratio of PHV to poly-3-hydroxybuyrate (PHB) production (ΔPHV/ΔPHB) ranged 1.2 ～ 3.4?mM-C/mM-C. PHV was produced faster and used later than PHB. By applying fluorescent in situ hybridization (FISH) technique, the percentage of Rhodocyclus-related bacteria to the total cell counts was monitored as an indicator of phosphorus accumulating organisms (PAOs). The population accounted for 38.3±16.2% at low organic loading rate and stayed at the same level as the organic loading rate increased.