Controlled Field Experiment for Performance Evaluation of Septic Tank Effluent Treatment during Soil Infiltration

Decentralized systems are responsible for treating approximately 25% of the wastewater generated in the United States. The most common decentralized system involves onsite treatment using a septic tank unit followed by dispersal to a subsurface soil infiltration unit where percolation to groundwater occurs. To evaluate the hydraulic and purification processes occurring during soil treatment of septic tank effluent (STE), a field experiment was initiated in the Spring of 2003 with continued operation and monitoring for 2 years. A replicated factorial design (22) was employed to evaluate three infiltrative surface architectures (ISAs) (open, stone, and synthetic) and two daily hydraulic loading rates (HLRs) (4 and 8?cm/day). Pilot-scale test cells were established in native sandy loam soils at the Mines Park Test Site located on the Colorado School of Mines campus in Golden, Colo. STE was obtained from a nearby multifamily apartment building and applied to the test cells daily. Field monitoring included baseline characterization of soil and site properties, routine characterization of the STE applied, observations of STE ponding on the infiltrative surface, periodic measurement of constant-head infiltration rates, and periodic sampling and analyses of the soil pore water at 60- or 120-cm depths below the infiltrative surface. Monitoring revealed that the ISA and HLR influenced the rate and extent of hydraulic capacity loss during soil treatment. For example, an open horizontal infiltrative surface maintained an infiltration capacity that was 40–80% higher than one covered with either washed stones or synthetic aggregate. Purification of STE during infiltration and percolation through the sandy loam soil was very high. The cumulative mass removed during 2 years of operation for dissolved organic carbon, total nitrogen, and total phosphorus averaged 94, 42, and 99%, respectively. While there was no significant difference in the purification performance based on ISA or HLR, an increase in the vadose zone depth slightly increased purification.     

Use of Layered Geotextiles to Provide a Substrate for Biomass Development in Treatment of Septic Tank Effluent Prior to Ground Infiltration

The use of layered geotextile filters for biological treatment of septic tank effluent prior to ground infiltration was investigated. The goal was to provide secondary treatment and prevent soil clogging by fostering biomass growth in the internal porosity of commercially available geotextiles. The study used primary effluent from a water pollution control facility that serves a combined sewer area. To identify sustainable operating conditions, the hydraulic loading rate (HLR) and other parameters were varied in tests with columns packed with multiple geotextile and granular layers. At continuous high hydraulic loading rate application, over 90% of total suspended solids and biochemical oxygen demand was removed, but the three layer filters eventually clogged. When a 365?L/m2?day?(9.0?gal/ft2?day) HLR was applied in dose and drain cycles to two filter layers, not only was there little loss in permeability, but ammonia (NH3) and nitrate (NO3?) concentrations in the effluent were reduced to below 5 and 10?mg/L, respectively. Scanning electron microscope images showed that the biomass morphology was not a continuous biofilm as was expected, but a discontinuous floc trapped within the geotextile pore structure. This provided intimate contact between substrate, oxygen, and biomass to produce the desired effluent quality and limited loss in filter permeability.     

Simultaneous Wastewater Nutrient Removal by a Novel Hybrid Bioprocess

A combined activated sludge–biofilm bioprocess called TNCU-I was developed by adding a rotating biological contactor to the aerobic zone of a traditional A2O process in order to solve the sludge retention time conflict between nitrifiers and phosphate accumulating organisms (PAOs), and the carbon source competition between denitrifiers and PAO. The TNCU-I process shows excellent carbon, nitrogen, and phosphate removal performance when treating synthetic wastewater. The process also achieved a more stable nitrification performance than the A2O process. The specific nitrification rate, the specific anoxic and aerobic phosphate uptake rates, the specific denitrification rate, and the specific anaerobic phosphate release rate were determined by a series of batch experiments. Such data were further analyzed to optimize the volume ratio of the TNCU-I anaerobic, anoxic, and aerobic tanks. The optimized process was also operated to confirm the performance. In addition, both Nitrosospira and Nitrospira were identified in the activated sludge and the rotating biological contactor biofilm by 16S rDNA based biotechnology.     

Hydrological Evaluation of Septic Disposal Field Design in Sloping Terrains

The most common form of onsite domestic wastewater treatment in the United States is the septic system. Although the design of these systems has been well established, no systematic evaluation of septic system performance exists for sloping hardpan soils. In this paper, we develop a simple hydrologic model for assessing the probability of failure for a set of hydrologic conditions, septic loading rates, and soil and landscape parameters that are readily available for sloping soils. To demonstrate the model capabilities, input data for a septic field of a two-person residence in the New York City drinking water basin in the Catskills was utilized. Our analysis showed that the saturated hydraulic conductivity, depth to the impermeable layer, and slope of the drain field are critical parameters to assess in the design and siting of these systems. We concluded that septic systems perform poorly in undulating landscapes where the hydraulic conductivity is low and the impermeable layer is close to the surface. Under prolonged rainfall conditions on these soils, the septic field and downslope field saturate, causing hydraulic failure of the septic system and saturation in the downslope field; as a result, effluent may be routed directly to streams via overland runoff.     

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.     

Model to Quantify Removal and Inactivation of Microorganisms Occluded in Effluent Wastewater Particles Using Filtration and Disinfection Systems

A model is presented to quantify microbial occlusion in effluent particles and improve understanding of the removal and inactivation of occluded microorganisms in filtration and disinfection systems. Microbial occlusion in particles is described in the model as a function of the particle size distribution, the microbial density (N1), which is the average quantity of target microorganisms within the subset of particles that contain microorganisms, and the frequency of association (N2), which is the ratio of particles that contain at least one target microorganism. To demonstrate the model, undisinfected secondary effluent samples were collected from an extended aeration treatment facility and analyzed to determine values for the model variables, N1 and N2 for heterotrophic bacteria and aerobic endospores and N2 for total coliform bacteria. Heterotrophic bacteria were present in most effluent particles (73–100%) at high densities (7–93 per particle), whereas aerobic endospores and total coliform bacteria were only present in a small percentage of effluent particles (0.1–6%) and the density of aerobic endospores in effluent particles was not appreciably higher than one per particle.     

Efficient Parallel Implementation of Hybrid Optimization Approaches for Solving Groundwater Inverse Problems

Inverse problems that are constrained by large-scale partial differential equation (PDE) systems demand very large computational resources. Solutions to these problems generally require the solution of a large number of complex PDE systems. Three-dimensional groundwater inverse problems fall under this category. In this paper, we describe the implementation of a parallel simulation-optimization framework for solving PDE-based inverse problems and demonstrate it for the solution of groundwater contaminant source release history reconstruction problems that are of practical importance. The optimization component employs several optimization algorithms, including genetic algorithms (GAs) and several local search (LS) approaches that can be used in a hybrid mode. This hybrid GA-LS optimizer is used to drive a parallel finite-element (FEM) groundwater forward transport simulator. Parallelism is exploited within the transport simulator (fine grained parallelism) as well as the optimizer (coarse grained parallelism) through the exclusive use of the Message Passing Interface (MPI) communication library. Algorithmic and parallel performance results are presented for an IBM SP3 supercomputer. Simulation and performance results presented in this paper illustrate that an effective combination of efficient optimization algorithms and parallel computing can enable solution to three-dimensional groundwater inverse problems of a size and complexity not attempted before.     

Hybrid Genetic Programming with Local Search Operators for Dynamic Force Identification

In this paper, based on the Darwinian and Lamarckian evolution theories, three hybrid genetic programming (GP) algorithms integrated with different local search operators (LSOs) are implemented to improve the search efficiency of the standard GP. These three LSOs are the genetic algorithm, the linear bisection search, and the Hooke and Jeeves method. A simple encoding method is presented to encode the GP individuals into the expressions that can be recognized by the different LSOs. The implemented hybrid GP algorithms are applied to identify the excitation force acting on the structures from the measured structural response, which is an important type of inverse problem in structural dynamics. Illustrative examples of a frame structure and a multistory building structure demonstrate that, compared with the standard GP, the hybrid GP algorithms have higher search efficiency which can be used as alternate global search and optimization tools for other engineering problem solving.     

Bricks from Petroleum Effluent Treatment Plant Sludge: Properties and Environmental Characteristics

A voluminous and hazardous sludge containing a high amount of hydrocarbons and several trace metals is generated in petroleum oil field effluent treatment plants. The aim of this study was to utilize the sludge in preparing environmentally acceptable masonry bricks in a commercial brick plant. The effect of the sludge on the plasticity behavior of the brick raw mix was investigated. The addition of the sludge reduces the requirement of process water and fuel. The fired bricks meet all the requirements of the Indian Standard Specification. The bricks were subjected to toxicity characteristics leaching protocol leaching tests. Most of the toxic metals are fixed in the vitrification process and the leachates values meet the Environmental Protection Agency’s requirement for recycling of hazardous materials.     

Postprocessing the Hybrid Method for Addressing Uncertainty in Risk Assessments

In a previous paper in this Journal, a “hybrid method” was proposed for the joint propagation of probability distributions (expressing variability) and possibility distributions (i.e., fuzzy numbers, expressing imprecision or partial ignorance) in the computation of risk. In order to compare the results of the hybrid computation (a random fuzzy set) to a tolerance threshold (a tolerable level of risk), a postprocessing method was proposed. Recent work has highlighted a shortcoming of this postprocessing step which yields overly conservative results. A postprocessing method based on Shafer’s theory of evidence provides a rigorous answer to the problem of comparing a random fuzzy set with a threshold. The principles behind the new postprocessing scheme are presented and illustrated with a synthetic example.     

Hybrid Time-Cost Optimization of Nonserial Repetitive Construction Projects

Time-cost trade-off analysis represents a challenging task because the activity duration and cost have uncertainty associated with them, which should be considered when performing schedule optimization. This study proposes a hybrid technique that combines genetic algorithms (GAs) with dynamic programming to solve construction projects time-cost trade-off problems under uncertainty. The technique is formulated to apply to project schedules with repetitive nonserial subprojects that are common in the construction industry such as multiunit housing projects and retail network development projects. A generalized mathematical model is derived to account for factors affecting cost and duration relationships at both the activity and project levels. First, a genetic algorithm is utilized to find optimum and near optimum solutions from the complicated hyperplane formed by the coding system. Then, a dynamic programming procedure is utilized to search the vicinity of each of the near optima found by the GA, and converges on the global optima. The entire optimization process is conducted using a custom developed computer code. The validation and implementation of the proposed techniques is done over three axes. Mathematical correctness is validated through function optimization of test functions with known optima. Applicability to scheduling problems is validated through optimization of a 14 activity miniproject found in the literature for results comparison. Finally implementation to a case study is done over a gas station development program to produce optimum schedules and corresponding trade-off curves. Results show that genetic algorithms can be integrated with dynamic programming techniques to provide an effective means of solving for optimal project schedules in an enhanced realistic approach.     

焦化废水零排放处理

焦化废水是一种较难处理的工业废水，按国内现有处理工艺很难达到一级排放标准。若根据不同的工业水质要求，将生化处理后废水直接回用，或进行深度处理后回用，既解决了废水外排造成的环境污染问题，叉提高了水的重复利用率，进而为焦化废水的零排放创造了有利条件。     

Potential of a Combination of UASB and DHS Reactor as a Novel Sewage Treatment System for Developing Countries: Long-Term Evaluation

A novel municipal wastewater treatment system, consisting of a combination of an upflow anaerobic sludge blanket (UASB) and down-flow hanging sponge (DHS) posttreatment unit, was continuously evaluated for more than three years with raw sewage as an influent. The system was installed at a sewage treatment site and operated at 25±3°C. This paper reports on the results of a long term monitoring of the system. The whole experimental period was divided into three distinct phases with different operating conditions. Organic pollutants were only partially removed in anaerobic UASB pretreatment unit. The remaining organics as well as nitrogenous compounds were almost completely removed by the DHS posttreatment unit. In all phases the system demonstrated removal efficiency consistently over 95% for unfiltered biochemical oxygen demand (BOD), 80% for unfiltered-chemical oxygen demand and 70% for suspended solids. The system produced an excellent effluent quality with only 4–9?mg/L of residual unfiltered BOD. Dissolved oxygen in the final effluent was 5–7?mg/L although no aeration was provided to DHS system. Moreover, excess sludge production from DHS was negligible thus eliminating secondary sludge that is troublesome to dispose off. The system also exhibited substantial stability against twofold hydraulic shock load and fourfold organic shock load. The results suggested that the proposed system may be a competitive solution for municipal sewage treatment under variable conditions.     

Mixing Water Treatment Residual with Excavation Waste Soil in Brick and Artificial Aggregate Making

A large quantity of water treatment residual is generated each year from fresh water treatment plants in Taiwan. Landfill disposal of the nonhazardous sludge is impractical because of the high cost of transportation and an increasing scarcity of landfill sites in Taiwan. The water treatment residual was characterized; the ceramic bodies were prepared and sintered to formulate into building bricks and artificial aggregates. The sintering temperature requirement by the water treatment residual was higher than normally practiced in brick works due to the higher Al2O3 and lower SiO2 content. The excavation waste soil, practically clay, was blended with water treatment residual to improve the brick quality. Under the commonly practiced brick-making condition, up to 15% of water treatment residual could be added to produce first grade brick specified by the National Science Council (NSC). Test results of specific gravity, water absorption, and compressive strength of the artificial aggregates confirmed its applicability in constructions as various degrees of light-weight aggregates.     

Coupled Creep and Seepage Model for Hybrid Media

The permeability coefficient of a rock mass depends mainly on the aperture of the joint and the porosity of the block, which may alter with time when creep of the rock mass is taken into account. Therefore, a coupled creep and seepage model for hybrid media is proposed in this paper. Large-scale and strongly permeable joints are simulated according to their spatial distributions, while other discontinuities are treated as equivalent continuum. Based on the fundamental mechanism of creep effects on the permeability of the rock mass, together with empirical equations for hydraulic conductivity, coupled creep and seepage equations for filled joints, rough joints, and equivalent continuum are proposed. By application of these equations, governing equations for the coupled creep and seepage model are deduced. A simplified numerical solution is proposed to solve the coupled creep and seepage model. The coupled model is shown to simulate the evolvement of seepage, deformation, and stress field in a gravity dam. By comparing the results derived by coupled and uncoupled models, it is concluded that the coupling between creep and seepage should be taken into account when performing engineering design of large dams.     

Experimental Validation of the Static Granular Bed Reactor for Industrial Waste Anaerobic Treatment

The static granular bed reactor (SGBR) is a unique high-rate anaerobic reactor designed to operate in a simple downflow manner, offering high chemical oxygen demand (COD) removal efficiencies (greater than 90%) resulting from high biomass retention in the system. A study was performed to evaluate the SGBR versus a control system, the upflow anaerobic sludge blanket (UASB) reactor, and to evaluate performance idiosyncrasies of the SGBR and the control. The two reactors were operated at three different hydraulic retention times (HRTs): 8, 16, and 24 h. The reactors treated synthetic wastewater, intended to simulate food industry waste, composed of sucrose and nonfat dry milk. Overall, COD removal was higher for the SGBR than for the UASB reactor. In particular, at a HRT of 8 h, the SGBR achieved a COD removal of 90.7% and the UASB reactor reduced the COD concentration by 77.5%. The UASB reactor’s specific COD loading factor proved rate limiting with values ranging from 0.19 to 0.94?gCOD/(gVS?d) versus 0.11 to 0.34?gCOD/(gVS?d) for the SGBR. A tracer study idealized hydraulics within the two systems, and the results showed minimal dead volume and 4–6% short circuiting for both reactors.     

Hybrid Soft Computing Approach for Mining of Complex Construction Databases

The paper presents a hybrid soft computing system for mining of complex construction databases. The proposed approach hybridizes soft computing techniques, such as fuzzy logic, artificial neural networks (ANNs), and messy genetic algorithms (mGAs), to form a novel computational method for mining of human understandable knowledge from historical databases. The hybridization combines the merits of explicit knowledge representation of fuzzy logic decision-making systems, learning abilities of ANNs, and global search of mGAs. A hybrid soft computing system (HSCS) is developed for mining complex databases in construction with three characteristics: scarcity, incompleteness, and uncertainty. Real-world construction data repositories are selected to test the capabilities of the proposed HSCS for data-mining under the above-mentioned complex conditions. The testing results show the promising potential of the proposed HSCS for mining of complex databases in construction.     

Comparative Study between a Hybrid System and a Biofilm System for the Treatment of Ammonia and Organic Matter in Wastewaters

The efficiency of two similar gas-lift bioreactors, a biofilm reactor and a hybrid circulating floating bed reactor (CFBR), were studied and compared. In the biofilm CFBR the biomass grew preferably adhered on a plastic granular support, whereas in the hybrid CFBR both suspended biomass and biofilms were allowed to grow in the reactor. COD/NH4+ ratio (COD=chemical oxygen demand) was manipulated between 0.0 and 8.0?g/g, maintaining the ammonia influent concentration around 50?mg N–NH4+/L, the ammonia loading rate at 0.9?kg N–NH4+/m3?day and the hydraulic retention time at 1.36?h. At low COD/NH4+ ratio (0 and 0.5?g/g) both systems behaved similarly, achieving ammonia removal percentages higher than 95%. In the biofilm CFBR a reduction of the nitrification percentage from 95 to 20% was observed when a COD/N–NH4+ ratio up to 8?g/g was applied in the influent. However, at the same operational conditions, the nitrification process in the hybrid CFBR was slightly affected. In the hybrid-CFBR reactor heterotrophs growing in suspension consumed the COD source faster than those growing in biofilms as was monitored. The growth of heterotrophic microorganism in suspension had a beneficial effect for the nitrifying population growing in the biofilm of the hybrid CFBR. Nitrifying activity of the biofilm was not limited by the presence of heterotrophs consuming dissolved oxygen, displacing the nitrifying bacteria or creating mass transfer resistance as was observed in the biofilm CFBR.     

Hybrid Method for Analysis of Segmented Shotcrete Tunnel Linings

When driving tunnels according to the New Austrian Tunneling Method. (NATM), shotcrete is applied onto the newly excavated areas of the tunnel surface. Large deformations occurring when driving tunnels under squeezing rock conditions lead to the destruction of a conventional shotcrete lining. As a remedy, segmented shotcrete linings characterized by an increased compliance have successfully been installed. In this paper a hybrid method for the analysis of such segmented tunnel linings is presented. It combines in situ displacement measurements with a thermochemomechanical material law for shotcrete. The application of this method to the Semmering pilot tunnel provides new insights into the load-carrying behavior of segmented tunnel linings.     

Framework to Support the Representations of Semantic Mappings for a Hybrid Integration Strategy

To provide an integrated information system for decision support, many previous studies focused on a strategy of sharing a common semantic model among heterogeneous data sources. Such a strategy has many advantages; however, it works only when it is possible for the heterogeneous data sources to share a common semantic model. For collaborating systems that cannot assume a prior knowledge of heterogeneity among them, a different strategy is needed. This paper, discussing a hybrid integration strategy and its applications to the architecture-engineering-construction industry, is focused on the development of a framework of semantic mappings so that high-level applications can use the mappings for data retrieval and processing. Based on a case study of integrating schedule and cost information, a prototype is developed to demonstrate the use of the framework, as well as to test the framework. Limitations and future studies are also discussed.