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.     

Making Asset Investment Decisions for Wastewater Systems That Include Sustainability

Effective integrated water management is a key component of the World Water Vision and the way in which aspirations for water equity may be realized. Part of the vision includes the promotion of sustainability of water systems and full accountability for their interaction with other urban systems. One major problem is that “sustainability” remains an elusive concept, although those involved with the provision of urban wastewater systems now recognize that decisions involving asset investment should use the “triple bottom line” approach to society, the economy, and the environment. The Sustainable Water Industry Asset Resource Decisions project has devised a flexible and adaptable framework of decision support processes that can be used to include the principles of sustainability more effectively. Decision mapping conducted at the outset of the project has shown that only a narrow range of criteria currently influence the outcome of asset investment decisions. This paper addresses the concepts of sustainability assessment and presents two case studies that illustrate how multicriteria decision support systems can enhance the assessment of the relative sustainability of a range of options when decisions are being made about wastewater asset investment.     

Low-Strength Wastewater Treatment with Combined Granular Anaerobic and Suspended Aerobic Cultures in Upflow Sludge Blanket Reactors

Combined cultures were developed from anaerobic granular and suspended aerobic cultures in three upflow sludge blanket reactors aerated at 10?mL air/min 4?h/day (R2), every other day (R3), and 24?h/day (R4). The use of combined cultures was found to be advantageous compared to the anaerobic granules for the treatment of low-strength wastewaters. During municipal wastewater treatment at influent 5-day biochemical oxygen demand (BOD5) concentration of 53–118?mg/L (hydraulic retention time: 0.75?day), combined cultures in R2, R3, and R4 exhibited average BOD5 removal efficiencies of 52, 75, and 76%, respectively. The use of these cultures might be proposed as an alternative for municipal wastewater treatment due to their advantages such as achievement of required discharge standards, prevention of biomass loss/settleability problems unlike activated sludge systems and possible methanogenic activity, as well as high settling characteristics comparable to those of anaerobic granules.     

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.     

Experimental Determination of Energy Content of Unknown Organics in Municipal Wastewater Streams

A bomb calorimetry method has been used for the first time to measure the energy content of raw municipal wastewater. The method was first validated using standard compounds (arginine, glucose, and propionic acid) and then tested with municipal sludge samples, with the results compared to previously published values. By drying a large enough sample to yield approximately 0.5 g of solid residue and using benzoic acid in a 1:1 ratio as a combustion aid, an accurate and precise measurement of the energy content of raw municipal wastewater can be made. The energy content measurements indicate that for the full-scale treatment facility examined, the potential energy available in the raw waste-water exceeds the electricity requirements of the treatment process by a factor of 9.3.     

New Protocol for the Enumeration of Salmonella and Shigella from Wastewater

Development of stringent standards for the microbiological quality of the wastewater has necessitated a sensitive and efficient method for the enumeration of pathogens present in wastewaters. Standard methods are used all over the world for the identification of microbes by the public health engineers. However, this conventional method has serious problems, which are related to the long detection time required for turbid wastewaters and corresponding reduced isolation of the microbes. The Conventional method has been modified by omitting the concentration and blending steps, and named as the “Direct method.” The Direct method should be able to provide maximum possible recovery specifically for the turbid wastewaters. An existing sewage treatment plant was selected to carry out the study over a period of six months. Samples were collected from the various stages of treatment and analyzed for the isolation of Salmonella and Shigella using the Conventional method and the proposed direct method. The direct method required less time compared to the Conventional method. More importantly, the recovery of Salmonella and Shigella has improved by 105% and 276%, respectively, over the Conventional method. The consistent improvement in the recovery of the pathogens has been seen at various stages of the sewage treatment.     

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.     

Nitrous Oxide Emissions and the Anthropogenic Nitrogen in Wastewater and Solid Waste

In the 20th century, human interference in the nitrogen cycle has caused a doubling of the global nitrogen fixation rate (an element critical in the proteins of all organisms), thereby intensifying global nitrous oxide (N2O) production during microbial nitrification and denitrification. Nitrous oxide is a powerful greenhouse gas, important in climate change, and as well, is a stratospheric ozone-depleting substance. It is likely that much of the Earth’s population now relies on anthropogenic nitrogen in its food supplies, resulting in anthropogenic nitrogen contained in wastes requiring management. Food production is considered as a source of global nitrous oxide emissions; however, the nitrogen in wastewater and solid wastes may be a significant fate of much anthropogenic nitrogen. This factor has largely escaped in-depth, critical analysis from the perspective of nitrous oxide emissions. This paper introduces nitrogen cycling and nitrous oxide production and reviews the research currently available on N2O emissions from wastewater treatment operations, landfilling, composting, and incineration; demonstrating that each process can emit large amounts of this important gas. This is followed by a discussion of the limited research. The relative importance of N2O in waste management is also estimated, indicating that wastewater treatment may be the most important operation for managing anthropogenic nitrogen in wastes.     

Anaerobic Filter Treatment of Municipal Wastewater: Biosolids Behavior

Three 12.5?L upflow anaerobic filter (AF) reactors, with ceramic saddle, plastic ring, and crushed stone packing, were employed to evaluate the treatment of raw municipal wastewater under a wide range of hydraulic and organic loadings and operating conditions. Emphasis is placed in this paper on column profile sampling, draining, and biomass evaluation studies conducted to ascertain the functioning of the reactors and accumulation of biosolids. The concentration of organics and solids within the AF gradually increased, starting at the low end and progressing to higher elevations. The peak chemical oxygen demand value measured within the reactors was 11,500?mg/L and was noted in the stone-packed unit at 20?cm after 1,009?days, and the stabilization of suspended material was greater in lower column sections. Packing material morphology influenced the removal by draining of entrapped biomass, and the volume of drainage recovered was substantially smaller than available void space. Biosolids retained in the saddle-packed unit after 34?months totaled 33?kg/1,000?m3 wastewater treated, and no signs of clogging were observed in any of the reactors.     

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.     

Nutrient Removal in a Cold-Region Wastewater Stabilization Pond: Importance of Ammonia Volatilization

Nitrogen (N), phosphorus (P), and carbon (C) flux through a three pond wastewater stabilization system (WWSP) was measured over the course of a year in a cold weather region (Minnesota) with 4?months of ice cover. The system was surprisingly efficient at N removal (averaging 80%) primarily through volatilization of un-ionized ammonia during the late spring when the pH was above 8 and ammonia levels were still high. P removal was less efficient, with over 50% of influent P leaving the system in the effluent. Soluble carbonaceous biochemical oxygen demand (CBOD) removal was >90%, with most of the removal occurring in the primary pond. Algal carbon requirements were met by a combination of CO2 released by bacterial oxidation of influent organic matter and inorganic carbon in the influent. Photosynthesis provided much of the oxygen needed for CBOD removal in the primary pond, and the onset of aerobic conditions was nearly coincident with the highest rates of ammonia volatilization. Bacterial respiration in the sediment returned >80% of the sedimented C back to the water column long term. These results demonstrate the importance of ammonia volatilization as a N sink in WWSPs that experience ice cover setting up conditions for both high primary production and high ammonia levels in spring.     

Computer Program Development for the Design of Integrated Fixed Film Activated Sludge Wastewater Treatment Processes

The Integrated Fixed Film Activated Sludge (IFAS) wastewater treatment systems are activated sludge biological nutrient removal processes that have been enhanced by the addition of biofilm support media into the aerobic zone of the system to obtain year round nitrification in activated sludge systems that otherwise could not support it. The objective of this study was to develop a computer package called “IFAS” that allows steady-state simulation of IFAS wastewater treatment processes based on the International Association Water Quality general model for activated sludge and empirical equations for chemical oxygen demand (COD) uptake and nitrification on integrated fixed film developed at Virginia Tech. The current version of the IFAS program supports only sponge-type media; however, the model could be modified for other media if the appropriate equations and required parameters values are known. Data obtained from IFAS sponge media pilot scale plants treating a weak municipal wastewater supplemented by sodium acetate, urea, sodium bicarbonate, and potassium phosphates and operated at different aerobic mean cells residence times were used to evaluate the model with parameter values for nitrification and COD uptake rates developed in batch studies. The model-generated ammonia and soluble COD profiles were insignificantly different statistically from the experimental data. The IFAS model satisfactorily predicts carbonaceous removal and nitrification, and has the potential to be a useful tool for scientists and engineers seeking to design and optimize either IFAS or conventional biological nutrient removal activated sludge systems.     

Evaluation of Integrated Fixed Film Activated Sludge Wastewater Treatment Processes at High Mean Cells Residence Time and Low Temperatures

Suspended solids mean cells residence time (MCRT) and temperature are two key parameters for designing Integrated Fixed Film Activated Sludge (IFAS) wastewater treatment processes, as an alternative for achieving year-round nitrification. It has been demonstrated from both full-scale and bench-scale studies that IFAS can accomplish year-round nitrogen removal and denitrification in aerobic zones in winter when operated with suspended growth MCRTs less than the critical MCRT for nitrifiers, thus avoiding increasing reactor or clarifier volumes. The objective of this study was to investigate the performances of IFAS systems that were operated at relative high MCRT compared to nitrifier washout MCRT and low temperature for biological nutrient removal. The comparison between two IFAS systems with Accuweb media in both the anoxic and aerobic zones, and a conventional three zone biological nutrient nemoval (BNR) system was conducted at 10°C with a 10 day MCRT using the UCT/VIP configuration for both systems and feeding with Blacksburg domestic wastewater. Influent flow was split 50% to the first anaerobic reactor and 50% to the first anoxic reactor to enhance denitrification in one of IFAS systems and the conventional BNR control system whereas 100% of the influent flow was fed to the first anaerobic reactor in the other IFAS system. The data from this investigation indicated that the performances of the control and IFAS systems were insignificantly different under the experimental operating conditions for both biological nitrogen and biological phosphorus removal except for IFAS with integrated fixed film media in the anoxic zone and when 50% of the influent was added directly to the first anoxic reactor.     

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.     

Biostorage Polymers Phenomena in Cheese Wastewater Treatment by a Sequencing Batch Reactor

Typically, microbes associated with biological wastewater treatment processes are subjected to dynamic organic and nutrient loading conditions. This constantly changing environment imposes a stress, referred to as “feast-famine” that selects for microbes capable of biologically storing substrates as polymers during high organic concentration periods (i.e., feast) for use during periods of low organic availability (i.e., famine). In this study, we monitored the production of biostorage polymers generated with actual cheese wastewater treatment by way of sequencing batch reactors (SBRs). SBRs were employed and operated in duplicate under two long (i.e., hours) filling scenarios (1) “react fill” with mixing/aeration and (2) “static fill” with no mixing/aeration. Despite comparable effluent water quality levels, the results reveal that a “static fill” approach outperforms a “react fill” with respect to maximum biostorage polymer production (50% more poly-β-hydroxybutyrate, 15% more glycogen). The presence of biostorage polymer production has been shown to be indicative of a more stable and robust process.     

Electrochemical Pretreatment of Wastewater from Bulk Drug Manufacturing Industry

The present study involves the treatment of high strength Bulk Drug Industry Wastewater by electrochemical method. The treatability studies were carried out with four different electrodes made of mild steel, aluminum, carbon, and stainless steel. The treatment efficiencies for chemical oxygen demand (COD)/biochemical oxygen demand (BOD), color, and heavy metal removals were assessed at different electrolysis time. A comparative study for heavy metal removal between chemical precipitation using aluminum and electrocoagulation with aluminum electrode has shown electrocoagulation to be more effective. Carbon electrode has shown COD removal of 34.0% and high BOD5f/CODf ratio of 0.581 at 120-min exposure time. Among all electrodes, aluminum was found as the most efficient in removal of color, suspended solids, and heavy metals with the least energy consumption of 95.83?Wh?kg?1?CODr and anode efficiency of 5.76?kg?COD?A?1?m?2?h?1. After electrochemical treatment, certain increase in BOD/COD ratio attributed to increase in biodegradability of wastewater. The study reveals that the wastewater could be effectively pretreated by electrochemical method.     

Electrochemical Oxidation and Ozonation for Textile Wastewater Reuse

Ozone and electrochemical oxidation treatment technologies were evaluated for wastewater recycling in the textile industry. Textile wastewater was collected from eight textile mills that use different dying processes. Both ozone and electrochemical oxidation removed the color from wastewater containing acid, reactive, and natural dyes, while mixed results were achieved with pigment and disperse dyes. The variability in color removal for the pigment and disperse dyes may be related to the concentration and type of auxiliary chemicals used. Color criteria for reusing wastewater for reactive dye was determined to be ΔE ? 2. This level of treatment provided an acceptable level of residual color for reuse in dark color dyeing operations and for rinse water. Some reformulation of the dye concentration and auxiliary chemicals is necessary for wastewater reuse in light color dyeing operations. Also, multiple reuse of the treated wastewater, as would occur in a completely closed system, would require changes in salt and other auxiliary chemicals to achieve the same fabric color as clean process water.     

Activated Sludge Process Modification for Sludge Yield Reduction Using Pulp and Paper Wastewater

Implications of conventional activated sludge (CAS) process modification to a low sludge production (LSP) process have been studied for treating pulp and paper wastewaters. The activated sludge process is modified to a two-stage design to establish a microbial food chain that would result in reduced sludge production. The return activated sludge in the LSP process bypasses the first (dispersed growth) stage to be received only by the second (predatory) stage. The resulting once-through operation of the dispersed growth (DG) stage makes it potentially susceptible to bacterial washout under hydraulic shock conditions. A sensitivity analysis of the DG stage operation was performed by varying its hydraulic residence time. The experimental data revealed that the optimal DG stage hydraulic residence is between 3 and 5?h, with bacterial washout likely to be initiated within 2?h. Based on laboratory results, it appears that a well-designed LSP system is likely to be able to handle day-to-day variations in hydraulic and organic loading rates. The LSP process produced 36% less sludge than the CAS process while consuming approximately 25% more oxygen. The treatment performance of the two systems was comparable except that the LSP sludge had much better settling and dewatering properties.     

Treatment of Polishing Wastewater from Semiconductor Manufacturer by Dispersed Air Flotation

Treatment of chemical mechanical polishing wastewater containing nanosized silica from semiconductor industry by dispersed air flotation was investigated. Very effective removal of particles from wastewater was found when cationic surfactant, cetyltrimethyl ammonium bromide (CTAB), was used as a collector. The flotation efficiency decreased slightly under a pH of 4.5. The zeta potential increased with a increasing concentration of CTAB, and flocculation of particles by CTAB was found. It is proposed that both the change of interface properties and the aggregation of particles contributed to flotation removal of particles. Longer reaction time and higher dosage were needed when n-dodecyl amine chloride (DAC) was used as a collector, owing to its relatively weak adsorption. The flotation efficiency increased with increasing DAC concentration. The improved flotation efficiency at pH of 10.0 was probably due to the formation of DAC precipitate.     

Industrial Plant for Olive Mill Wastewater from Two-Phase Treatment by Chemical Oxidation

Olive-oil production generates high and variable amounts of wastewaters from the olives and olive-oil washing (OMW), resulting to great environmental impact. These waters are normally stored in large holding ponds for evaporation during the summer. The present study examines the chemical-oxidation process using ferric chloride catalyst for the activation of H2O2 (Fenton reaction). Tests have been made on an industrial scale. The final average value of chemical oxygen demand (COD) was close to 371?mg?O2?L?1 (%CODremoval = 86%, CODinitial = 2684?mg?O2?L?1), and the water produced can be used for irrigation or can be discharged directly into the municipal wastewater system for tertiary treatment.