This paper presents a comparison between three simple sewage treatment lines involving natural processes: (a) upflow anaerobic sludge blanket (UASB) reactor-three maturation ponds in series-coarse ...rock filter; (b) UASB reactor-horizontal subsurface-flow constructed wetland; and (c) vertical-flow constructed wetlands treating raw sewage (first stage of the French system). The evaluation was based on several years of practical experience with three small full-scale plants receiving the same influent wastewater (population equivalents of 220, 60 and 100 inhabitants) in the city of Belo Horizonte, Brazil. The comparison included interpretation of concentrations and removal efficiencies based on monitoring data (organic matter, solids, nitrogen, phosphorus, coliforms and helminth eggs), together with an evaluation of practical aspects, such as land and volume requirements, sludge production and handling, plant management, clogging and others. Based on an integrated evaluation of all aspects involved, it is worth emphasizing that each system has its own specificities, and no generalization can be made on the best option. The overall conclusion is that the three lines are suitable for sewage treatment in small communities in warm-climate regions.
Horizontal flow wetlands have been designed using the so-called P-k-C* approach, which has been largely embraced by the treatment wetlands literature. P is meant to represent the equivalent number of ...apparent tanks in series (hydraulic factor), but also incorporates the loss of biodegradability as the wastewater undergoes treatment (kinetic factor). For design purposes, literature proposes fixed values of P. The proposal of this paper is to decouple hydraulics from kinetics and use the traditional concept of N or NTIS (number of tanks in series) as a function of geometric relationships of the wetland to be designed, leaving kinetic elements to be dealt with solely by the first-order removal rate coefficient (k). From the literature, a database with 41 wetlands with data from tracer studies was used, and a novel regression-based equation was derived relating N with the ratio length/depth of horizontal wetlands. This equation can be used at the design stage for estimating N and, hence, the output concentration of the pollutant using the traditional structure of the TIS model, with a possible inclusion of background concentration (C*). The paper presents all relevant equations, including those from the plug-flow with dispersion model (PFD), and it is shown how to convert from one hydraulic model to the other, what is also believed to be a novel approach in the treatment wetland literature. Finally, the area-based removal rate coefficients (kA) proposed by Kadlec and Wallace (2009) for designs of horizontal wetlands treating domestic wastewater based on the P-k-C* approach are converted into kA values for the TIS model in the paper.
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•Utilization of the TIS model for the design of horizontal flow wetlands is proposed.•Estimation of the number of TIS can be made based on the wetland ratio length/depth.•Equations for areal-based and volumetric-based TIS and PFD models are presented.•TIS and PFD give virtually the same estimation of effluent concentrations.•An adaptation of removal rate coefficients from P-k-C* to TIS and PFD models is made.
Basic Principles of Wastewater Treatment is the second volume in the series Biological Wastewater Treatment, and focusses on the unit operations and processes associated with biological wastewater ...treatment. The major topics covered are: microbiology and ecology of wastewater treatment reaction kinetics and reactor hydraulics conversion of organic and inorganic matter sedimentation aeration The theory presented in this volume forms the basis upon which the other books of the series are built. About the series: The series is based on a highly acclaimed set of best selling textbooks. This international version is comprised by six textbooks giving a state-of-the-art presentation of the science and technology of biological wastewater treatment. Other titles in the series are: Volume 1: Wastewater Characteristics, Treatment and Disposal; Volume 3: Waste Stabilisation Ponds; Volume 4: Anaerobic Reactors; Volume 5: Activated Sludge and Aerobic Biofilm Reactors; Volume 6: Sludge Treatment and Disposal
"Waste Stabilisation Ponds is the third volume in the series Biological Wastewater Treatment. The major variants of pond systems are fully covered, namely: facultative ponds anaerobic ponds aerated ...lagoons maturation ponds The book presents in a clear and informative way the main concepts, working principles, expected removal efficiencies, design criteria, design examples, construction aspects, operational guidelines and sludge managment for pond systems. About the series: The series is based on a highly acclaimed set of best selling textbooks. This international version is comprised by six textbooks giving a state-of-the-art presentation of the science and technology of biological wastewater treatment. Other titles in the series are: Volume 1: Waste Stabilisation Ponds Volume; 2: Basic Principles of Wastewater Treatment; Volume 4: Anaerobic Reactors; Volume 5: Activated Sludge and Aerobic Biofilm Reactors; Volume 6: Sludge Treatment and Disposal"
•The clogging solids are predominantly inorganic.•The greater source of clogging solids is the wear of the filter material.•The organic solids influence most the pore spaces, due to their greater ...volume.•Near the outlet, the solids characteristics are closer to those of the substrate.
The influent solids load, biofilm formation and occupation of void spaces by precipitates have been identified as major contributors to clogging the pores of horizontal subsurface flow constructed wetlands (HSSF-CWs). Several publications suggest that most of the accumulated material is inorganic, and this indicates that wear of the substrate may be an important constituent of clogging. The objective of this study was to characterize, in mineralogical, physical (specific mass) and chemical terms (neutralization power and volatile and fixed solids) the clogging material from the pores and the substrate medium (blast furnace slag) in two small full-scale HSSF-CWs, one planted with cattail (Typha latifolia) and another kept unplanted. The system received urban wastewater pre-treated in an upflow anaerobic sludge blanket reactor, was operating for seven years and showed signs of heavy clogging leading to overland flow. Samples were collected at intermediate points along the two units in order to identify the origin of the accumulated material and thereby enable the proposition of a conceptual model for the clogging process of these systems. The results indicated that most of the mass of clogging solids were inorganic and originated from wear of the substrate. However, the volume occupied by the organic solids was larger, and those were the major contributors to the clogging process.
This article presents a reliability analysis of 166 full-scale wastewater treatment plants operating in Brazil. Six different processes have been investigated, comprising septic tank+anaerobic ...filter, facultative pond, anaerobic pond+facultative pond, activated sludge, upflow anaerobic sludge blanket (UASB) reactors alone and UASB reactors followed by post-treatment. A methodology developed by Niku et al. 1979. Performance of activated sludge process and reliability-based design.
J. Water Pollut. Control Assoc., 51(12), 2841–2857 is used for determining the coefficients of reliability (COR), in terms of the compliance of effluent biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP) and fecal or thermotolerant coliforms (FC) with discharge standards. The design concentrations necessary to meet the prevailing discharge standards and the expected compliance percentages have been calculated from the COR obtained. The results showed that few plants, under the observed operating conditions, would be able to present reliable performances considering the compliance with the analyzed standards. The article also discusses the importance of understanding the lognormal behavior of the data in setting up discharge standards, in interpreting monitoring results and compliance with the legislation.
Activated Sludge and Aerobic Biofilm Reactors is the fifth volume in the series Biological Wastewater Treatment. The first part of the book is devoted to the activated sludge process, covering the ...removal of organic matter, nitrogen and phosphorus.A detailed analysis of the biological reactor (aeration tank) and the final sedimentation tanks is provided. The second part of the book covers aerobic biofilm reactors, especially trickling filters, rotating biological contractors and submerged aerated biofilters. For all the systems, the book presents in a clear and informative way the main concepts, working principles, expected removal efficiencies, design criteria, design examples, construction aspects and operational guidelines. About the series: The series is based on a highly acclaimed set of best selling textbooks. This international version is comprised by six textbooks giving a state-of-the-art presentation of the science and technology of biological wastewater treatment.
Identification of the degree of porous medium clogging in constructed wetlands (CWs) is a complex procedure because bed obstruction is a phenomenon that occurs in the subsurface and involves several ...factors. Ideal methods must allow for subsurface analysis and be non-invasive, what is the case of ground penetrating radar (GPR or georadar) used for soil characterization. Thus, this work aimed to evaluate the use of GPR for clogging characterization of two full-scale horizontal subsurface flow constructed wetlands (HSSF-CWs), one unit planted with cattail (Typha latifolia) and the other unit with no vegetation. Both units received municipal sewage (50 p.e. each) previously treated in an anaerobic reactor, had been in operation for seven years (at the time the GPR was used) and showed signs of heavy clogging, leading to surface flow. In order to produce a standard for GPR image (created by the response of the reflected wave in the passage through different media) identification and association of colors with the environmental conditions inside the medium (cleaner or more obstructed condition), a clean granular rock filter (in operation for only one month), similar to the unplanted unit, was used. Equations developed for indirectly estimating the porosity, based on the RGB (red, green and blue) color scale, indicated that the methodology was in agreement with the visual conditions of surface flow occurrence in the HSSF-CW, showing to be a suitable non-invasive method to characterize the advancement of clogging in CWs.
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•GPR shows to be a promising way to assess the clogging degree in CW;•The method allows the estimation of a possible surface flow occurrence;•The developed equations allow porosity estimation;•The methodology reduce visual interpretation subjectivity.
Waste stabilisation ponds are applied all over the world for treating domestic wastewater. In many developing countries, they constitute the most widely used treatment process, and incorporate the ...important function of pathogen removal. Because of this wide utilisation, ponds have been extensively studied, resulting in new insights on the disinfection mechanisms, thus leading to more efficient systems and lower land and volume requirements. The previous “black-box” approach for pond design is being substituted by a more conceptual view resulting from a better understanding of pathogen removal mechanisms. This review manuscript aims at gathering previous and current research done on this matter, concentrating on coliforms, and evaluating the following mechanisms and influencing factors: temperature; sedimentation and attachment; dissolved oxygen and pH levels; sunlight-mediated disinfection (in combination with DO and pH) and dark inactivation/repair; biological disinfection (predation, starvation and competition); algal toxins; depth and hydraulic retention time; physical design and hydrodynamic behaviour. Gaps that still need to be filled are identified, which could still lead to further optimisation of waste stabilisation ponds performance.
The paper presents a very extensive evaluation of the coliform decay in facultative and maturation ponds, based on data from 186 different ponds in the world. The ponds encompass a very wide ...diversity in terms of physical and operating conditions, covering most situations encountered in practice. The median values for the coliform removal efficiencies were 1.8
log units (98% removal) for primary facultative ponds, 1.0
log units for secondary facultative ponds (90% removal) and 1.2
log units (94% removal) for each maturation pond in the series. Two equations to be used for design purposes were derived for estimating the die-off coefficient
K
b (dispersed flow, 20
°C) in facultative and maturation ponds. The first equation led to a slightly better fitting with the observed logarithm of the effluent coliform concentrations (
R
2
=
0.874
), and related
K
b with the pond detention time
t and depth
H (
K
b
=
0.682
H
–
1.286
t
–
0.103
). The other equation also led to a satisfactory fitting (
R
2
=
0.845
), but was slightly simpler, depending only on the pond depth (
K
b
=
0.549
H
–
1.456
).
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