Effect of Organic Surface Load on Process Performance of Pilot-Scale Algae and Duckweed-Based Waste Stabilization Ponds

Removal efficiencies in pilot scale algae-based ponds (ABPs) and duckweed-based ponds (DBPs) were assessed during two periods of 4 months each. During Periods 1 and 2, the effect of low and high organic loading was studied. A linear correlation between ponds organic surface loading rates and the corresponding biochemical oxygen demand (BOD) removal rates was observed in both systems. For both periods, higher BOD and total suspended solids (TSS) removal efficiencies were found in DBPs compared to ABPs. Nitrogen removal rates (λr) in ABPs were linearly correlated with BOD surface loading rates (λs,BOD) and nitrogen loading rates (λs,N), while in DBPs, N removal rates were almost constant irrespective of λs,BOD or λs,N. Overall N removal rate in the algae system was significantly higher than that in duckweed system. Organic loading had no effect on total phosphorus removal efficiency in both systems. Higher P removal efficiency was achieved in the duckweed system than in the algae system. In ABPs as well as DBPs, fecal coliforms were better removed during low organic loading in comparison with high organic loading. During the two operational periods, higher fecal coliform removal efficiency in the algae system than in the duckweed system was observed.     

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.     

Seasonal Operation of Ponds for Chemical Precipitation of Wastewater

Wastewater precipitation ponds (fellingsdams) are conventional stabilization ponds adapted to cold climate by the use of chemical precipitation to attain sufficient removal efficiency of impurities, primarily phosphorus. The objective with this investigation was to study the influence of an interruption of the dosage of coagulant during summer periods at two fellingsdam systems (Orrviken and Lockne) in the middle of Sweden. The investigation took place over two years characterized by unusual precipitation conditions; 2001 was intense in precipitation whereas summer 2002 represented a dry season. The results showed that there is a potential to utilize the summer biological activity in fellingsdams. At Orrviken the effluent quality measured as organic matter and phosphorus in the effluent was just slightly above the values that were reached by chemical precipitation. At Lockne the performance was lower. The organic matter reduction at Orrviken in the summers of 2001 and 2002 were 71 and 67%, respectively, compared to previous years using precipitant when the average was 78%. At Lockne, however, the values in the summers of 2001 and 2002 were 36 and 18%, respectively, compared to previous years using precipitant when the average was 55%. The phosphorous reduction at Orrviken in the summers of 2001 and 2002 were 85 and 89%, respectively, compared to previous years using precipitant when the average was 95%; at the Lockne plant, the phosphorous reduction during the summers of 2001 and 2002 were 60 and 66%, respectively, compared to the previous years' average of 86%. The nitrogen reduction varied considerably over the two summer periods. The reduction at Orrviken was 13% in 2001 and 58% in 2002; the reduction at Lockne was 13% in 2001 and 33% in 2002. Reference values of nitrogen reduction during normal operations were not available.     

Identifying and Assessing Influence Factors on Improving Waste Management Performance for Building Construction Projects

Environmental sustainability has become one of the key drivers for continuous growth in the construction industry. Many project practitioners face challenging circumstances in finding an effective way to prevent pollution and minimize wastes by making the best use of the increasingly scarce natural resources. However, most of these efforts are focused on planning and/or design strategies; therefore, they fail to thoroughly cover the environmental issues based on the construction execution level. Further, there is a lack of quantitative measurement system and management-level guidance. To overcome these limitations, this paper proposes a new methodology that assists project managers to assess the performance level of a project in terms of waste management practice. This study is based on a two-pronged approach. One is the identification of the waste management influence factors that play an important role in decreasing waste and increasing recycled materials on construction sites. The other is the development of an assessment tool to measure the level of waste management performance for a particular project. As a result of this work, 59 factors were identified and an assessment tool was developed based on quantification of these factors. The tool has been proved to effectively measure waste management performance throughout four real-case validity tests. From the industry perspective, this paper contributes to establishing the environmentally sustainable production systems by providing the project stakeholders with an established set of influence factors and with a diagnosis tool for measuring their current performance. Additionally, project owners can use the output of the tool, especially the total index score, as a measure to benchmark the level of waste management for continuous improvement.     

Novel Design Concept for Facultative Ponds Using Rock Filters to Reclaim the Effluent

This paper presents a novel design concept for using rock filters as in-line natural media in waste stabilization ponds. A pilot-scale algae-rock-filter pond (ARP) system was investigated in parallel with algae-based ponds (ABPs) over a period of 6 months to evaluate the treatment efficacy of both systems. Each system entailed four equally sized ponds in a series and was continuously fed with domestic wastewater from Birzeit University. The removal rates of organic matter, nutrients, and fecal coliforms were monitored within each treatment system. The results obtained revealed that the ARP system was more efficient in the removal of organic matter [total suspended solids (TSS) and chemical oxygen demand (COD), 86% and 84%, respectively] and fecal coliforms (4log?) than the ABP system (81%, 81%, 3log?, respectively). The ARPs showed higher removal rates for ammonium and phosphorus (68.8% and 50.0%, respectively) compared with the ABPs (57.9% and 41.5%, respectively). The biogenic-aerated ARP option is a cost-effective and land-saving alternative with effluent quality suitable for restricted agricultural irrigation. The ARPs utilizing a new algae-biofilm design concept should be investigated at a large scale to enhance the information available to relevant decision makers, who are seeking sustainable on-site wastewater treatment alternatives.     

Comparison of Computation Fluid Dynamics Simulation against Tracer Data from a Scale Model and Full-Sized Waste Stabilization Pond

The use of computation fluid dynamics (CFD) for waste stabilization pond design is becoming increasingly common but there is a large gap in the literature with regard to validating CFD pond models against experimental flow data. This paper assesses a CFD model against tracer studies undertaken on a full-sized field pond and then on a 1:5 scale model of the same pond operated under controlled conditions in the laboratory. While the CFD tracer simulation had some discrepancies with the field data, comparison to the laboratory model data was excellent. The issue is, therefore, not in the way the model solves the problem, for example, the choice of turbulence model or differencing scheme, but rather with how accurately the physical conditions in the field are defined. Extensive survey of the sludge layer and transient input of changing flow rates, wind velocities, and temperature could allow closer alignment of CFD simulations to field data. However, in the practical application of CFD where a modification such as baffle installation results in a large change, then a simple pragmatic model, while not exact, can still provide valuable design insight.     

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.     

Aerated Rock Filters for Enhanced Ammonia and Fecal Coliform Removal from Facultative Pond Effluents

Rock filters used to treat effluents from waste stabilization ponds do not remove ammonia as they are anoxic. A pilot-scale aerated rock filter was investigated, in parallel with an unaerated control, over an 18-month period to determine whether aeration provided conditions within the rock filter for nitrification to occur. Facultative pond effluent containing ～ 10?mg NH4–N/L was applied to the filters at a hydraulic loading rate of 0.15?m3/m3?day during the first 8?months and at 0.3?m3/m3?day thereafter. The results show that the ammonia and nitrate concentrations in the effluent from the aerated filter were <3 and ～ 5?mg?N/L, respectively, whereas the ammonia concentration in the effluent from the control filter was ～ 7?mg?N/L. Fecal coliforms were reduced in the aerated filter to a geometric mean count of 65?per?100?mL; in contrast the effluent from the control filter contained 103–104 fecal coliforms per 100?mL. Aerated rock filters are thus a useful land-saving alternative to aerobic maturation ponds.     

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.     

Developing a Web-Based System for Large-Scale Environmental Hydraulics Problems with Application to Oil Spill Modeling

Oil spill models are used for decision making during emergencies, contingency planning, and risk assessment. Many of these oil spill models are desktop based. A typical desktop model system is served by an input and output interface to communicate with the user. In a desktop model system, all components reside in the user’s computer. The development of a Web-based model system (Web-CDOG) for large-scale environmental hydraulics problems with an application to oil spill modeling is presented in this paper. The Web-CDOG provides a number of advantages and features that are not available through a desktop system. It helps users to access the model, improves user-developer communication, gives the user access to distributed data, restricts some user access to data (e.g., direct transfer of data from third party sites to the model system without allowing user access), classifies users with different levels of accessibility, and allows multiple users to access the same data. Other examples where a similar Web-based system could be useful include modeling sediment plumes and deepwater oil well blowouts.     

Metals Removal from Municipal Waste Incinerator Fly Ashes and Reuse of Treated Leachates

Incinerator fly ash from municipal solid waste is considered as a hazardous waste and can release toxic metals such as Pb and Cd into the environment. This research verifies the performance of a sequential, closed circuit treatment process involving chemical leaching (alkaline washings followed by an acid washings) and precipitation (neutralization at pH = 5 and 7). This method also includes the recirculation of treated leachates during the acid washing steps. In total, ten recirculation loops were executed in laboratory pilot scale. The three alkaline leaching steps effectively solubilized the leachable Pb. Two acid leaching steps were required to solubilize Cd, Al, and Zn. Toxic metals, Cd and Pb, were removed from the fly ash at 72 and 30%, respectively. The toxicity characteristic leaching procedure (TCLP), the synthetic precipitation leaching procedure (SPLP), and a simple test using neutral water were conducted on the treated ash in order to validate the process. The results obtained were below the norm for the TCLP and near 0.01?mg/L of Cd and Pb in solution for the other two tests. The removal efficiency during the precipitation step were 21% Cd, 99% Pb, 100% Al, and 63% Zn. The metallic residue produced at pH = 7 contained 23% Zn which is potentially recyclable in the metallurgical industry. The recirculation of treated leachates reduced water consumption for the decontamination process by 60%.     

Application of Natural Clayey Soil as Adsorbent for the Removal of Copper from Wastewater

Use of clayey soil has been explored in the laboratory scale experiment as a low cost adsorbent for the removal of copper from wastewater. The influence of metal ion concentration, weight of adsorbent, stirring rates, influence of temperature, pH are also evaluated and the results are fitted using adsorption isotherm models. From the experimental results it is observed that almost 90–99% copper can be removed from the solution using clay at optimized pH 5.5. Langmuir adsorption isotherm, Freundlich isotherm and Tempkin isotherm model have been used to describe the distribution of copper between the liquid and solid phases in batch studies and it has been observed that Langmuir isotherm better represents the phenomenon. From the experimental results rate constant, activation energy, Gibbs free energy, enthalpy, and entropy of the reaction are calculated to determine the mechanism of the sorption process. Thomas, Adams-Bohart, and Yoon-Nelson models are applied to the experimental data to determine the characteristic parameters of the column for process design.     

Luminol-Based Enhanced Chemiluminescence Assay for Quantification of Peroxidase and Hydrogen Peroxide in Aqueous Solutions: Effect of Reagent pH and Ionic Strength

The effect of reagent pH and ionic strength was evaluated on the horseradish peroxidase (HRP)-luminol-p-iodophenol enhanced chemiluminescence assay. This assay was optimized for HRP and H2O2 quantification during enzyme-mediated remediation of groundwater or wastewater contaminated with phenolic chemicals. The maximum chemiluminescence intensity (ICLmax) and total area under the chemiluminescence intensity profiles were measured as a function of p-iodophenol concentration, reagent solution pH, and reagent ionic strength. ICLmax values were optimum at pH 8.5 and increased linearly with reagent ionic strength. Optimum chemiluminescence enhancement was produced at a p-iodophenol concentration of 0.3 mM under the reaction conditions. ICLmax values were linearly correlated with HRP and H2O2 concentrations within the ranges of 0.1–1 activity units/mL and 0.1–1 mM, respectively. Results indicate that the HRP-luminol-p-iodohenol enhanced chemiluminescence assay has a potential to be used for quantification of HRP activity and H2O2 concentration in aqueous solutions encountered in groundwater remediation or wastewater treatment scenarios.     

Application Framework for Mapping and Simulation of Waste Handling Processes in Construction

This research is focused on modeling waste-handling processes in construction, with particular emphasis on how to map out and simulate on-site waste sorting processes. The research proposes an application framework for (1) guiding the development of process mapping models and simulation models; and (2) further assessing the cost effectiveness of on-site waste sorting efforts under practical site constraints (such as labor resource availability, time control on refuse chute usage, and limited working area space in a building site). The connection has been established between the mapping and simulation techniques in the context of modeling waste handling processes in construction sites, such that the process flowchart resulting from the mapping technique can serve as convenient model input to facilitate the creation of a “dynamic” operations simulation model. A case study of the on-site waste sorting method with one refuse chute for waste classification is presented to demonstrate the complete application framework spanning (1) process mapping; (2) mapping-to-simulation model conversion; and (3) method optimization based on valid simulations.     

Modeling the Oxidation of Sulfide in Pulp and Paper Wastewaters

Reactor experiments were conducted to study aerobic sulfide oxidation in pulp and paper wastewaters under typical operating conditions. Data produced from these experiments were used to develop a set of sequential rate equations that describe the significant sulfide and oxygen processes in the reactors. Model parameters were estimated for three different pulp and paper wastewaters using a multiresponse procedure. The sulfide oxidation rate coefficients for the wastewaters ranged from 0.108 to 0.155?min?1 at 35°C and approximately neutral pH. The reaction order with respect to oxygen could not be precisely estimated but appeared to be near the lower boundary for the fitting procedure (essentially zero order). Modeling of the oxygen depletion data provided evidence that the first sulfide oxidation reaction product consumed 0.5 mg of oxygen per mg of sulfide oxidized, suggesting polysulfides and elemental sulfur as the initial reaction products. The oxygen depletion modeling also suggested oxidation of the initial reaction product to a more stable intermediate which is postulated to be thiosulfate.     

冲击波清灰技术在锌沸腾焙烧余热锅炉中的应用

介绍锌精矿沸腾焙烧余热锅炉烟气性质,分析锅炉清灰方案设计思路,详细介绍了冲击波清灰的原理、安装及调试方法。根据两年多的生产实践,说明冲击波清灰完全满足生产工艺要求,而且具有免维护、运行费用省、操作简单等优点。     

Factors Affecting Effectiveness and Efficiency of DNAPL Destruction Using Potassium Permanganate and Catalyzed Hydrogen Peroxide

This paper describes laboratory studies conducted to evaluate the impact of varying environmental conditions (dense nonaqueous phase liquid (DNAPL) type and mass, and properties of the subsurface porous media) and design features (oxidant type and load) on the effectiveness and efficiency of in situ chemical oxidation (ISCO) for destruction of DNAPL contaminants. Porous media in 160?mL zero-headspace reactors were employed to examine the destruction of trichloroethylene and perchloroethylene by the oxidants potassium permanganate and catalyzed hydrogen peroxide. Measures of oxidation effectiveness and efficiency include (1) media demand (mg-oxidant/kg-porous media), (2) oxidant demand (mol-oxidant/mol-DNAPL), (3) reaction rate constants for oxidant and DNAPL depletion (min?1), (4) the percent (%) DNAPL destroyed, and (5) the relative treatment efficiency, i.e., the rate of oxidant depletion versus rate of DNAPL destruction. While an obvious goal of ISCO for DNAPL treatment is high effectiveness (i.e., extensive contaminant destruction), it is also important to focus on oxidation efficiency, or to what extent the oxidant is utilized for contaminant destruction instead of competing side reactions, for improved cost effectiveness and/or treatment times. Results indicate that DNAPL contaminants can be treated both effectively and efficiently under many environmental and design conditions. In some cases, DNAPL treatment was more effective and efficient than dissolved/sorbed phase treatment. In these experiments, permanganate was a more effective oxidant, however catalyzed hydrogen peroxide treated contaminants more efficiently (e.g., less oxidant required per mass contaminant treated). Results also indicate that oxidation treatment goals can be dictated by environmental conditions, and that specific treatment goals can dictate remediation design parameters (e.g., faster contaminant destruction was realized in catalyzed hydrogen peroxide systems, whereas greater contaminant destruction occurred in permanganate systems).     

Quality, Environmental, and Health and Safety Management Systems for Construction Engineering

The philosophy behind quality, environmental, and safety (QES) management systems is a concept that has been accepted by various contractors. Furthermore, a process has been developed insuring that the output produced conforms to customer satisfaction without violating any environmental, health, and safety rules and regulations. An effective QES program not only assures a quality product but also reduces costs, and enhances productivity. It is a top down process, i.e., top management together with line management and other employees develop the program and motivate all personnel to accept the process. Important functions to take under consideration are (1) explain and clarify the quality, environmental, and safety performance expected; (2) involve employees in decision-making and problem solving; (3) describe the consequences of poor quality and unsafe/unhealthy work conditions; (4) establish QES goals and provide feedback on performance; (5) provide a self-monitoring system; and (6) recognize and reinforce good performance and develop a reward system. This paper presents a discussion of the development of a portion of a QES management system which has been employed by a medium to large size construction company. In particular, Items 1–4, listed above, are described in detail.     

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.