bluuebunny/crossref_metadata_2025 huggingface dataset:
UV disinfection for reuse applications in North America
Authors: Sakamoto G. , Schwartzel D. , Tomowich D.
Published: May 2018

In an effort to conserve and protect limited water resources, the States of Florida and California have actively promoted wastewater reclamation and have implemented comprehensive regulations covering a range of reuse applications. Florida has a semi-tropical climate with heavy summer rains that are lost due to run off and evaporation. Much of California is arid and suffers periodic droughts, low annual rainfall and depleted ground water supplies. The high population density combined with heavy irrigation demands has depleted ground water supplies resulting in salt-water intrusion. During the past decade, Florida reuse sites have increased dramatically from 118 to 444 plants representing a total flow capacity of 826 MGD. California presently has over 250 plants producing 1 BGD with a projected increase of 160 sites over the next 20 years.

To prevent the transmission of waterborne diseases, disinfection of reclaimed water is controlled by stringent regulations. Many states regulate wastewater treatment processes, nutrient removal, final effluent quality and disinfection criteria based upon the specific reuse application. As a rule, the resulting effluents have low turbidity and suspended solids. For such effluents, UV technology can economically achieve the most stringent disinfection targets that are required by the States of California and Florida for restricted and unrestricted reuse.

This paper compares UV disinfection for wastewater reuse sites in California and Florida and discusses the effect of effluent quality on UV disinfection.
Influence of the free water content on the dewaterability of sewage sludges
Authors: Kopp J. , Dichtl N.
Published: May 2018

Dewaterabilty of sewage depends on the physical water distribution. The various types of water in sewage sludge are mainly distinguished by type and intensity of their physical bonding to the solids. In a sewage sludge suspension different types of water can be distinguished. These are free water, which is not bound to the particles, interstitial water, which is bound by capillary forces between the sludge flocs, surface water, which is bound by adhesive forces and intracellular water. Only free water can be separated during mechanical dewatering. It can be shown, that thermo-gravimteric measurement of the free water content leads to an exact prediction of full-scale dewatering results. Maximum dewatering results are reached by separating all free water during centrifugation. Furthermore on the basis of the drying curve an estimation of water binding energies can be achieved. The binding energy for free water is less than 0,28 kJ/kg water. The binding energy for bound water (sum of surface and intracellular water) is higher than 5 kJ/kg water.
Sludge reduction potential of metazoa in membrane bioreactors
Authors: Luxmy B.S. , Kubo T. , Yamamoto K.
Published: May 2018

In order to check the sludge reduction capacity of metazoa in a membrane bioreactor (MBR), pilot-scale studies were conducted. Three MBRs had been set in a wastewater treatment plant at Tokyo, Japan and they were receiving real wastewater. Initially pH inside the three MBRs was controlled as pH 7, 6 and 5 respectively. Then metazoa population was monitored along with MLSS change. It was found that the presence or absence of the metazoa population did not have any significant effect on the increasing pattern of MLSS. In the MBR with pH 6 highest accumulation of sludge was observed though a high and steady level of metazoa (1,000-2,000 per ml) was present there. But in this MBR a lot of metazoa attached in the membrane was also observed and here the increase in transmembrane pressure was less than in the other two. So, metazoa population especially the attached one in the membrane plays an effective role in fouling control of the membrane. Presence of attached media may provide a suitable niche for metazoa in the process. So, attached media known as DB lace was also inserted in MBRs for testing its capacity along with inoculum of oligochaete worms. Accumulation of sludge was not satisfactory in the attached string and it seems that inoculated worm could not adjust to the environment as they were not sludge originated. So, in the next experimental stage, attached media was inserted in the form of a bundle and this time no inoculation of worm was used. A steady metazoa population was observed in the system but the accumulation of sludge in the attached media was the same as before.
Advanced biological unit processes for domestic water recycling
Authors: Jefferson B. , Laine A. L. , Stephenson T. , Judd S. J.
Published: May 2018

The potential of advanced biological unit operations for the recycling of grey and black waters has been evaluated. The membrane bioreactor (MBR) demonstrated the greatest efficacy towards water recycling in terms of all the quality determinants. Both the biologically aerated filter (BAF) and the MBR were able to effectively treat the organic and physical pollutants in all the types of wastewater tested. The main difference was observed in terms of the microbiological quality, measured as total coliforms. The open bed structure of the BAF enabled passage of coliforms whereas the complete barrier of the MBR produced a non detectable level in the effluent. The MBR process complied with commonly adopted water recycling quality standards for the all determinants during the grey water trials and failed only in terms of total coliform counts once black water had been introduced into the feed. The MBR was seen as a particularly suitable advanced biological process as it was very effective at stabilising out the considerable load variations encountered during the trial.
Effect of carbon to nitrogen ratio on the composition of microbial extracellular polymers in activated sludge
Authors: Durmaz B. , Sanin F.D.
Published: May 2018

Effect of carbon to nitrogen ratio (C/N) on the sludge extracellular polymer composition is studied in synthetically fed semi-continuous reactors with 8 days of sludge age. Results show that C/N ratio influences the relative distribution of polymer carbohydrate and protein. At low C/N ratio of 5, polymer extracts have high protein and low carbohydrate content. As the C/N ratio is increased to 17.5 and then to 40, carbohydrate concentration increases sharply and protein concentration decreases.
Membrane filtration of wastewater effluents for reuse: effluent organic matter rejection and fouling
Authors: Jarusutthirak C. , Amy G.
Published: May 2018

The reuse of treated wastewater to augment natural drinking water supplies is receiving serious consideration. Treatment of secondary and tertiary effluent by membrane filtration was investigated by assessing nanofiltration (NF) membrane and ultrafiltration (UF) membranes in bench-scale experiments. It was found that secondary and tertiary effluent contained high concentration of effluent organic matter (EfOM), contributing EfOM-related fouling. Flux decline and EfOM rejection tests were evaluated, using a dead-end stirred cell filtration unit. Surface charge and molecular weight cut-off (MWCO) of membranes were significant factors in membrane performance including permeability and EfOM-rejection.
Potential and limitations of alum or zeolite addition to improve the performance of a submerged membrane bioreactor
Authors: Lee J. C. , Kim J. S. , Kang I. J. , Cho M. H. , Park P. K. , Lee C. H.
Published: May 2018

In this study, alum and natural zeolite were added to a submerged membrane bioreactor (MBR) not only to reduce membrane fouling but also to increase the removal of nitrogen and phosphorus. Alum addition reduced significantly the rising rate of suction pressure and also resulted in stable and better COD removal. Although phosphorus removal was more than 90% by chemical precipitation, nitrification inhibition was observed. With the addition of natural zeolite, membrane permeability was greatly enhanced by the formation of rigid floc that had lower specific resistance than that of the control activated sludge floc. In particular, the nitrification efficiency was over 95% even at N-shock loading due to the ion-exchange capacity of zeolite. The mechanisms for improved membrane permeability through alum or zeolite addition were discussed in detail.
Flotation with polyelectrolytes as a first step of a more sustainable wastewater treatment system
Authors: Mels A. R. , Rulkens W. H. , van der Meer A. K. , Nieuwenhuijzen A. F. , Klapwijk A.
Published: May 2018

Within the framework of a research programme into more sustainable wastewater treatment systems based on physical-chemical pretreatment the application of dissolved air flotation (DAF) with polyelectrolytes as a primary treatment was investigated. Experiments with municipal wastewater were carried out in 2.5 l flotation batches and in a 100 l DAF pilot reactor. Two cationic polyelectrolytes (PEs) with molecular weights of 4×106 g/mol and 8×106 g/mol, were tested. The higher weight PE was more effective in removing turbidity and was used in the pilot experiments for coagulation/flocculation. Within the pilot system experiments the dry solids concentration of the float layer as well as the removal efficiencies of turbidity, CODparticulate, CODdissoIved and nutrients, were studied. Typical results were that the obtained dry solids concentration of the floated sludge was 10%, when the float layer was removed after several hours. By using polyelectrolytes it was possible to remove more than 80% of CODparticulate and turbidity at dosages of 7-8 mg/g influent COD (i.e. 5 mg PE/l00 NTU). The removal efficiency of CODdissolved was low. There was a proportional relationship between CODparticulate and turbidity. This led to the conclusions that by introducing a dosing control strategy based on continuous turbidity measurements a constant CODparticulate removal efficiency can be obtained.
UV dose distribution characterization using fractal concepts for system performance evaluation
Authors: Lin L.-S. , Blatchley E. R.
Published: May 2018

This paper presents a mathematical model for estimating the UV dose distribution delivered by continuous-flow UV disinfection processes. The model adopts fractal concepts and a stochastic method to simulate microorganism (particle) trajectories through the irradiation zone of an open-channel UV system. The irregularity of particle trajectories attributable to random movements was characterized by fractal dimension. In turn, trajectory-specific doses were calculated by integrating UV intensity over travel time. Results of these simulations indicated that radiation intensities along the trajectories could be highly variable. Therefore, microorganisms are expected to receive a broad range of radiation doses as a result of variations in radiation intensity along their trajectories and spatial heterogeneity in the radiation intensity field. This supports previous assertions that the conventional averaged-dose approach will result in substantial deviations between predicted and actual system performance. Implications of the results in terms of treatment efficiency and system design are discussed. The presented approach is found to be useful as a tool for rapid estimation of the dose distribution delivered by UV processes.
New methods for the detection of viruses: call for review of drinking water quality guidelines
Authors: Grabow W.O.K. , Taylor M.B. , de Villiers J.C.
Published: May 2018

Drinking water supplies which meet international recommendations for source, treatment and disinfection were analysed. Viruses recovered from 100 L-1,000 L volumes by in-line glass wool filters were inoculated in parallel into four cell culture systems. Cell culture inoculation was used to isolate cytopathogenic viruses, amplify the nucleic acid of non-cytopathogenic viruses and confirm viability of viruses. Over a period of two years, viruses were detected in 23% of 413 drinking water samples and 73% of 224 raw water samples. Cytopathogenic viruses were detected in 6% raw water samples but not in any treated drinking water supplies. Enteroviruses were detected in 17% drinking water samples, adenoviruses in 4% and hepatitis A virus in 3%. In addition to these viruses, astro- and rotaviruses were detected in raw water. All drinking water supplies had heterotrophic plate counts of <100/mL, total and faecal coliform counts of 0/100 mL and negative results in qualitative presence-absence tests for somatic and F-RNA coliphages (500 mL samples). These results call for a revision of water quality guidelines based on indicator organisms and vague reference to the absence of viruses.
Occurrence of Cryptosporidium oocysts and Giardia cysts in a conventional water purification plant
Authors: Hashimoto A. , Hirata T. , Kunikane S.
Published: May 2018

A one-year monitoring of Cryptosporidium oocysts and Giardia cysts was conducted at a water purification plant. A total of thirteen 50 L samples of river source water and twenty-six 2,000 L samples of filtered water (treated by coagulation-flocculation, sedimentation and rapid filtration) were concentrated using a hollow fibre ultrafiltration membrane module at a purification plant. Cryptosporidium oocysts were detected in all raw water samples with a geometric mean concentration of 400 oocysts/m3 (range 160-1,500 oocysts/m3). Giardia cysts were detected in 12/13 raw waters (92%) with a geometric mean concentration of 170 cysts/m3 (range 40-580 oocysts/m3). Probability distributions of both Cryptosporidium oocyst and Giardia cyst concentration in raw water were nearly log-normal. In filtered water samples, Cryptosporidium oocysts were detected in 9/26 samples (35%) with a geometric mean concentration of 1.2 oocysts/m3 (range 0.5-8 oocysts/m3) and Giardia cysts in three samples (12%) with 0.8 cysts/m3 (range 0.5-2 oocysts/m3). The estimated removal of Cryptosporidium oocysts and Giardia cysts was, respectively, 2.54 log10 and 2.53 log10 on the basis of geometric means, 3.20 and 3.57 log10 on the basis of 50% observation level and 2.70 and 2.90 log10 on the basis of 90% observation level.
Comparative survival of enteric viruses and bacteria in Atlantic Ocean seawater
Authors: Wait D. A. , Sobsey M. D.
Published: May 2018

The survival of Escherichia coli, Salmonella typhi, Shigella sonnei, poliovirus type 1 and a parvovirus (Minute Virus of Mice) was determined in seawater. Seeded seawater was incubated in the laboratory at 6, 12, 20 and 28°C for up to 40 d. In-situ survival studies were done seasonally (winter, spring, summer and fall) using seeded microbial dialysis equipment placed in the Atlantic Ocean off coastal North Carolina at water depths of 3–10 m. In laboratory studies all test microbes survived longer at lower temperatures with typical times for 90% inactivation (T90) of 1–3 d at the highest temperature and >10 d at the lowest temperature. Of the microbes tested, E. coli survived least well while S. typhi and Sh. sonnei survived similar to or greater than enteric viruses. Parvovirus survival was similar to that of poliovirus. Under in-situ conditions, E. coli also survived least well of all microbes tested with T90 values of 0.9–3.9 d depending upon season. All other test microbes had generally similar survivals. Overall, microbial survival in seawater was greater under laboratory conditions than under in-situ conditions. There was no clear association between microbial survival and water temperature. The lower survival of E. coli compared to the bacterial and viral pathogens under laboratory conditions raises concerns because it is a key microbial indicator of faecal contamination.
Water quality improvement of treated wastewater by intermittent soil percolation
Authors: Castillo G. , Mena M. P. , Dibarrart F. , Honeyman G.
Published: May 2018

Our research aimed to evaluate intermittent soil infiltration of treated sewage for reuse in the north of Chile. Aerated lagoon effluent was infiltrated in columns packed with native soils (sandy-lime, lime-gravel and limey-sand). Columns were operated for more than a year under different cycles of filling and drying, depths and load pressures depending on soil characteristics. The efficiency of the system was determined through influent-effluent microbiological indicators level (faecal coliforms, E. coli, Salmonella spp, MS2 phage, and protozoan cysts), physicochemical characterisation (TOC, COD, BOD, nitrogen), and hydraulic flow measurement. Results showed: (a) high reduction of enteric bacteria (5–7 log10), some inactivation of phage (2–4 log10) and complete removal of intestinal cyst; (b) stable removal of organic matter (80–90% reduction of TOC, COD, BOD); and (c) partial ammonia reduction through adsorption and nitrification with denitrification mainly occurring in sandy soil. Preliminary data from pilot plant working in the field showed better results that those obtained in the laboratory especially removal of microbiological indicators. Microbiological quality of effluent met Class A regulations for agricultural reuse (WHO, 1989) and the system looks like an attractive alternative to cope with water shortage in the region.
Planning of wastewater treatment and disposal systems of Istanbul metropolitan area
Authors: Eroglu V. , Sarikaya H. Z. , Aydin A. F.
Published: May 2018

Current and future wastewater treatment and disposal strategies of Istanbul city are presented. Istanbul is the largest city of Turkey and has a population of 10 million that may reach about 20 million in 2032. The city is divided into Asian and European sides by the Bosphorus Strait. The Sea of Marmara is an enclosed sea, connected to the Black Sea and Aegean Sea by the straits of Bosphorus and Dardanelles. Therefore, there is very strong and permanent stratification in the Sea of Marmara throughout the year, lower layers carrying Mediterranean and the upper layers carrying Black Sea water. This unique coastal structure of Istanbul necessitated a detailed study to determine the level of wastewater treatment and the location and depth of marine outfalls.

A comprehensive three-dimensional water quality modelling study concluded that tertiary treatment including nitrogen and phosphorus removal is required for the effluent discharges into the Marmara Sea. However, enhanced primary or even primary treatment has been found satisfactory for discharges into the lower layers of the Bosphorus and into the Black Sea. Provisions for upgrading to secondary treatment were recommended. The status of existing and planned wastewater treatment plants and sea outfalls of Istanbul city are also presented. Although the amount of treated wastewater was only 63 percent in 1998, a target of 95 percent treatment level by the end of 2000 has been adopted in implementation plans. All treatment plants are located at or close to the coast except Pasakoy WWTP which is in the catchment area of Omerli Reservoir, the major source of drinking water for Istanbul city. The Pasakoy WWTP has been designed to treat wastewaters collected from the catchment area of Omerli Reservoir to tertiary level before ultimate disposal. The implementation programme together with the cost estimates are given. Total investment on water, wastewater and stormwater projects up to year 2032 is estimated at about 10 billion US Dollars. The share of the wastewater projects in this total is increasing with time. The financial analysis concluded that investments for a Higher Demand Scenario can be realised by raising the water tariffs to 1.0 $/m3 for Phase 1 and 0.9 $/m3 for Phase 2.
Benchmarking - an approach to efficiency enhancement in planning, construction and operation of wastewater treatment plants
Authors: Stemplewski J. , Schulz A. , Schön J.
Published: May 2018

In the following paper the technique of benchmarking was transferred to the field of wastewater treatment. The method was developed within a pilot project, in which 4 wastewater treatment plants (WWTP) (size category: 10,000-100,000 p. e.) of the Emschergenossenschaft/Lippeverband and the Aggerverband were involved. Meanwhile this method is applied to more than 100 WWTP. Specific technical and economic parameters were determined for the whole treatment plant and afterwards assigned to the different treatment steps. With these numbers differences between the examined plants and the respective benchmarks were visible. On the basis of the following cause analysis a schedule could be developed containing at first measures, which could be translated into action immediately. The less obvious reasons for differences between individual numbers required a deeper cause analysis. Because of external influences not all the plants can reach the benchmarks.
Using the World Wide Web to revolutionise technology transfer and training in the water and wastewater industries
Authors: Lant P. A. , Emmett D.
Published: May 2018

Industry professionals of the near future will be supported by an IT infrastructure that enables them to complete a task by drawing on resources and people with expertise anywhere in the world, and access to knowledge through specific training programs that address the task requirements. The increasing uptake of new technologies enables information to reach a diverse population and to provide flexible learning environments 24 hours a day, 7 days a week. This paper examines one of the key areas where the World Wide Web will impact on the water and wastewater industries, namely technology transfer and training. The authors will present their experiences of developing online training courses for wastewater industry professionals over the last two years. The perspective is that of two people working at the “coalface”.
The effect of acid cleaning on a fine pore ceramic diffuser aeration system
Authors: Hung C.-H. , Boyle W. C.
Published: May 2018

Fine pore ceramic diffuser aeration, a very competitive high efficiency system, is widely used in aerobic biological processes for providing dissolved oxygen and mixing. Concern has been registered regarding the maintenance of these systems and their susceptibility to diffuser fouling. Selected ceramic diffusers, removed from the Madison Metropolitan Sewage District (MMSD) Nine Springs Wastewater Treatment Plant, Wisconsin, U.S.A., were fractured and analyzed in an attempt to identify the elemental components of the internal foulants and to evaluate the effect of acid cleaning on diffuser performance. The fouling condition of diffusers were initially characterized by dynamic wet pressure (DWP) measurements. Microimages taken from the non acid-treated diffuser profile using scanning electronic microscopy revealed the structural difference of internal foulants which may correspond to the stage of foulant formation. For diffuser samples from the MMSD facility, calcium phosphate minerals were predominant foulants, although some calcium carbonate and organic carbon have also accumulated. The clogging of diffuser internal void space was verified by observing thin sections of diffuser cross-sections. Selected diffusers were then treated with strong acid to study its effectiveness in removing internal foulant by acid soaking. Even though the acid treated diffusers showed significant reduced DWP values, acid treatment, the common diffuser cleaning technique, does not completely remove these internal foulants. This may be the reason why the acid-treated diffusers never reached like-new conditions. Furthermore, once these acid-treated diffusers are installed back to the aeration tank, these dewatered foulant sections may very well behave as seed for future clogging.
Self-monitoring of water quality in sewer systems using absorbance of ultraviolet and visible light
Authors: Ruban G. , Yuperd Y. , Laveau B. , Lucas E.
Published: May 2018

Continuous pollution measurement is interesting to optimize the operation of sanitary facilities as well as to minimize the stormwater discharges. An experimental study was carried out for the determination of Suspended Solids (SS) and Chemical Oxygen Demand (COD) concentrations in combined sewers using ultraviolet and visible absorbances. The maintenance of the measurement system requires six hours a month for the cleaning of the hydraulic feeding system and adjustment of the optical device. The feeding system developed increased the representativeness and reliability of the pollution measurement, but needs to be validated on other measurement sites. The determination of SS concentrations from visible absorbances requires 2 calibration curves for dry and rainy weather respectively. The corresponding accuracies appear satisfactory when compared with the results of standard sampling/laboratory analysis. The accuracy of COD determination from ultraviolet absorbance is less satisfactory, but could perhaps be improved taking into account another parameter. Then the optical measurement of SS and COD is interesting to determine average or long term pollution loads, for example the yearly impact of urban stormwater discharges. With this kind of continuous and on-line measurement, it is possible to react with short delay to unexpected phenomena which could damage the environment or water treatment efficiency.
Optimisation of operational management practices for the detention basins
Authors: Jacopin C. , Lucas E. , Desbordes M. , Bourgogne P.
Published: May 2018

The objective of this study is to develop new operational management practices for detention basins during rainfall events in order to limit flooding risk and, at the same time, to reduce pollutant discharges by optimising the settling process. For this work, a methodology was developed to study the integration of the stormwater treatment into existing detention structures. In this article, it was applied on two experimental sites. The current operation of the basins and “on/off” regulation studies were first carried out to quantify the freedom to act to change the control schemes. Relying on the support of these studies, new operational rules based on the current or “on/off” principle were then elaborated and tested on the experimental basins using a hydraulic model. Finally, their efficiency to protect against flooding and to reduce pollutant discharges was assessed.
Municipal wastewater sludge dewaterability and the presence of microbial extracellular polymer
Authors: Houghton J. J. , Quarmby J. , Stephenson T.
Published: May 2018

Dewatering of sewage sludge is an essential and costly part of the wastewater treatment process. The presence of microbial extracellular polymer (ECP) is important for sludge flocculation, but ECP has also been shown to have a detrimental effect on the dewaterability of certain sludge types. This paper investigates the relationship between sludge dewaterability and the level of ECP present in a range of sludges obtained from 8 full-scale municipal treatment works in the UK. Sludge dewaterability was determined using the capillary suction time (CST) test, and a thermal extraction process followed by solvent precipitation was used for ECP extraction. The results indicate that for each type of sludge examined there appears to be an optimum level of ECP (raw sludge 20 mg ECP/g SS; activated sludge 35 mg ECP/g SS; digested sludge 10 mg ECP/g SS) at which the sludge should exhibit maximum dewaterability. The establishment of a trend between sludge dewaterability and the quantity of ECP present opens up the possibility of manipulating the level of microbial polymer present to aid sludge dewatering, and hence reduce plant operating costs.
Vane shear strength of dewatered sludge from Hong Kong
Authors: Koenig A. , Bari Q. H.
Published: May 2018

The vane shear strength and total solids content of dewatered sludge from Hong Kong were determined in order to evaluate their geotechnical suitability for disposal in landfills. The results obtained indicate that (i) the total solids and vane shear strength of dewatered sludge from different treatment plants varied considerably depending on the type of sludge and dewatering method; and, (ii) percent total solids alone is not sufficient to guarantee geotechnical stability in terms of vane shear strength. The critical state model for soils provided a good fit for the characteristic relationship between vane shear strength and total solids, which can be used to estimate vane shear strength from total solids only. No relationship between volatile solids and vane shear strength was found. The results of the laboratory vane shear test correlated well with those obtained by a pocket shearmeter indicating the usefulness of this method for rapid determination of vane shear strength on site. Some factors that influence vane shear strength were briefly evaluated. Implications of the results for sludge management with special emphasis on dewatering and landfilling were discussed.
Chemical characteristics and leachability of organically contaminated heavy metal sludge solidified by silica fume and cement
Authors: Jun K.-S. , Hwang B.-W. , Shin H.-S. , Won Y.-S.
Published: May 2018

This paper discusses the development of mixtures with silica fume as a stabilization/solidification agent and binder for industrial wastewater residue containing organic and heavy metal contaminants. The UCS (Unconfined Compressive Strength) gradually increased to 66.7% as the silica fume content increased to 15%. The leaching of TOC and chromium decreased as more OPC was substituted with silica fume. When the mix had 5% silica fume, it retained about 85% TOC, and chromium leached out 0.76mg-Cr/g-Cr in acidic solution. Also, microstructural studies on the solidified wastes through the scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and X-ray diffraction analysis showed that the silica fume caused an inhibition to the ettringite formation which did not contribute to setting, but coated the cement particles and retarded the setting reactions. The results indicated that the incorporation of silica fume into the cement matrix minimized the detrimental effects of organic materials on the cement hydration reaction and contaminant leachability.
Size and structure effects on centrifugal dewatering of digested sewage sludge
Authors: Feitz A. J. , Guan J. , Waite T. D.
Published: May 2018

The application of light scattering over small angles for the determination of digested sludge floc size and structure and its relationship with dewaterability is investigated. It appears that improved dewatering corresponds with lower floc fractal dimension (a more open structure) and a smaller proportion of fine particles. The initial increase in fractal dimension with increasing polymer dose for the digested sludge is most likely due to more efficient aggregation of the finer particles and the resulting formation of denser particle aggregates. A large colloidal fractal of the digested sludge (< 10 μm) appears to be less negative than the bulk digested sludge. This suggests that the fine particles will react differently and possibly less aggressively to the cationic polymer than the larger and more negative particles. The higher negative charge associated with the larger particles might be related to greater levels of highly negatively charged extracellular polysaccharides (EPS) adsorbed to the flocs or could result from the association of FeS with the finer fraction. The appearance of much greater levels of fine particles after digestion suggests that the flocs have undergone disintegration. Whether this is due to reduced biological efficiency within the digestor or iron reduction under the anaerobic conditions is not known for certain, although no indication of prolonged stress in the digesters could be found from plant performance data.
Surface flow (SF) treatment wetlands as a habitat for wildlife and humans
Authors: Knight R.L , Clarke R.A. , Bastian R.K.
Published: May 2018

Water quality improvement is generally the primary objective of treatment wetlands. Creation of wildlife habitat is an inevitable outcome of these projects. However, an increasing number of treatment wetland projects have been purposely designed and operated to enhance their beneficial utility to wildlife and humans. This trend to multi-purpose treatment wetlands has broadened the basis for assessing the advantages of this natural treatment alternative. There are at least 21 treatment wetlands in the U.S. that were implemented with wildlife habitat creation and/or human use as principal goals. A number of treatment wetlands outside the U.S. also share these priorities. Hundreds of other wetlands have collected and reported quantitative data on wildlife and/or human uses. The North American Treatment Wetland Database (NADB) has been expanded to include critical wildlife habitat and human use data. This paper provides a preliminary inventory of these habitat and human use treatment wetlands, summarizes lessons learned, and identifies additional data needs.
Environmental impacts to the Everglades ecosystem: a historical perspective and restoration strategies
Authors: Chimney M.J. , Goforth G.
Published: May 2018

The Everglades is a vast subtropical wetland that dominates the landscape of south Florida and is widely recognized as an ecosystem of great ecological importance. As a result of anthropogenic disturbances over the past 100 years (i.e., agricultural and urban development, eutrophication resulting from stormwater runoff, changes in hydrology and invasion of exotic species), the biotic integrity of the entire Everglades is now threatened. To protect this valuable resource, the state of Florida and the Federal Government, in cooperation with other interested parties, have developed a comprehensive restoration strategy that addresses controlling excess nutrient loading and reestablishment of a more natural hydrology. These efforts include building approximately 17,000 ha of treatment wetlands, referred to as Stormwater Treatment Areas, to treat surface runoff before it is discharged into the Everglades. We briefly discuss the history of the Everglades in the context of environmental disturbance and outline the steps being taken to ensure its survival for future generations.
Evaluation of phosphorus retention in a South Florida treatment wetland
Authors: Nungesser M.K. , Chimney M.J.
Published: May 2018

The Everglades Construction Project of the South Florida Water Management District (District) will employ large constructed wetlands known as Stormwater Treatment Areas (STAs) to reduce phosphorus concentrations in runoff entering the Everglades. The District built and operated a prototype STA, the 1,545 ha Everglades Nutrient Removal Project (ENRP), to determine the efficacy of subtropical wetlands for improving regional water quality with a focus on reducing total phosphorus (TP). In five years of operation, the ENRP has consistently exceeded its performance goals of TP outflow concentrations <50 μg P/L and a 75% TP load reduction.

Since August 1994, the ENRP has retained 70.3 metric tons of TP that otherwise would have entered the Everglades. When corrected for surface area and inflow TP load, TP removal efficiency was highest in the inflow buffer cell and decreased generally in a downstream fashion through the wetland. High TP removal efficiency in treatment cell 4 was attributed to superior performance of its submerged aquatic vegetation community relative to the emergent and floating macrophyte community in the other cells. Controlled experiments in the District's STA Optimization Research Program will help clarify what effect vegetation and operational conditions may have on nutrient removal in the STAs.
Progress in the research and demonstration of Everglades periphyton-based stormwater treatment areas
Authors: Bays J.S. , Knight R.L. , Wenkert L. , Clarke R. , Gong S.
Published: May 2018

The South Florida Water Management District (District) is conducting research focused on potential advanced treatment technologies to support reduction of phosphorus (P) loads in surface water entering the remaining Everglades. Periphyton-based stormwater treatment areas (PSTA) are one of the advanced treatment technologies being researched by the District. This detailed research and demonstration project is being conducted in two phases. Basic research in field-based mesocosm experiments was conducted during the first phase within the District's Everglades Nutrient Removal Project (ENR). Studies were conducted in 24 portable PSTA mesocosms and three of the south ENR test cells. Phase 1 studies addressed the effects of system substrate (shellrock, organic peat, or sand), water depth, hydraulic loading rate, vegetation presence, depth:width ratio, and inhibition of algal growth on total phosphorus removal performance of the PSTA mesocosms. A second phase of research is currently under way, during which PSTA feasibility will be evaluated further in four field-scale constructed mesocosms totaling about 2 ha, and follow up studies within the ENR test cells and portable mesocosms will be conducted to further investigate the effects of other inorganic substrates, shallow water depth, and velocity on treatment performance. Phase 1 monitoring has determined that periphyton-dominated communities can be established in constructed wetlands within 5 months. The algal component of these periphyton plant communities is characteristic of natural Everglades periphyton. High macrophyte densities resulted from use of peat soils in PSTA mesocosms, while shellrock and sand soils promoted more desirable sparse macrophyte stands. P removal rates under the conditions of this research were relatively high considering the low influent total P concentrations tested (average 23 μg/L). PSTA mesocosms on shellrock soils were able to attain long-term average outflow total P concentrations as low as 11 μg/L. The maximum one-parameter TP first-order removal rate constant (k1) measured was 27 m/y. Minimum attainable outflow total P concentrations and mass removals appear to be the result of a balance between internal P loading from antecedent soils, uptake and burial processes in new sediments, and rainfall inputs. A different soil type (limerock) will be tested for effectiveness during Phase 2. Selected existing treatments will also be continued to look for trends over a second growing season.
Microbial indicator removal in onsite constructed wetlands for wastewater treatment in the southeastern U.S.
Authors: Barrett E.C. , Sobsey M.D. , House C.H. , White K.D.
Published: May 2018

Seven onsite constructed wetlands for wastewater treatment in the coastal plains of Alabama and North Carolina were studied from September 1997 to July 1998. Each site was examined for its ability to remove a range of fecal contamination indicators from settled wastewater. Indicator organisms include total and fecal coliforms, enterococci, Clostridium perfringens, and somatic and male-specific (F+) coliphages. Four identical domestic wastewater treatment sites in Alabama were evaluated. In these sites the Log10 geometric mean reductions ranged between 0.5 and 2.6 for total and fecal coliforms, 0.1 and 1.5 for enterococci, 1.2 to 2.7 for C. perfringens, -0.3 and 1.2 for somatic coliphages, and -0.2 and 2.2 for F+ coliphages. Three unique designs were examined in North Carolina. Log10 geometric mean reductions ranged between 0.8 to 4.2 for total and fecal coliforms, 0.3 to 2.9 for enterococci, 1.6 to 2.9 for C. perfringens, -0.2 and 2.8 for somatic coliphages, and -0.1 and 1.5 for F+ coliphages. Somatic and F+ coliphage detection was highly variable from month to month.
Distribution and retention of faecal coliforms in the Nakivubo wetland in Kampala, Uganda
Authors: Kansiime F. , van Bruggen J.J.A.
Published: May 2018

Nakivubo wetland, which has been receiving wastewater from the capital of Uganda for more than 40 years is a tropical wetland dominated by Cyperus papyrus and Miscanthidium violaceum. Field, pilot and laboratory studies were carried out to assess the distribution of faecal coliforms and factors responsible for their retention in different compartments of the two macrophytes in the wetland. There were higher coliform numbers in the free water column below the mat of zones dominated by Miscanthidium (1.1±0.6×105 MPN/100 ml) compared to those dominated by papyrus (8.9±3.1×104 MPN /100 ml). The thick (1.3 m) and compact mat of Miscanthidium restricts vertical transport of wastewater into the mat, resulting in flow-through of wastewater under the mat. The papyrus mat is loose, open and thin (0.5 m) and allows easy vertical penetration of wastewater into the mat. The unrestricted interaction between the wastewater in the water column and that in the mat of papyrus in addition to plant debris and detritus continuously sedimenting out of the mat to the wetland bottom are responsible for the retention of coliforms in the papyrus dominated zones. Attachment, sedimentation and natural die-off were found to be important mechanisms responsible for the retention of coliforms in the Nakivubo wetland.
Biota participating in wastewater treatment in a horizontal flow constructed wetland
Authors: Vymazal J. , Sládeček V. , Stach J.
Published: May 2018

During the period 1996-1997, three constructed wetlands with sub-surface horizontal flow were investigated. All systems are designed to treat municipal sewage from small villages (150, 200 and 300 PE). The survey included microscopical identification of organisms in both wastewater and filtration substrate. The organisms were used as an indication of oxygen conditions (aerobic, anoxic and anaerobic) in the particular microenvironment. Saprobiological terms characterizing different levels of saprobity were employed to characterize inflowing wastewater, filtration bed and outflowing water. The occurrence of organisms was correlated with BOD5 values in particular profiles. It has been found that the biocenosis in the inflowing wastewater differs from those found in the filtration bed and water outflowing from the vegetated beds. The organisms were grouped into those living under anaerobic and anoxic conditions and those living under aerobic conditions. More than 70 species of bacteria, amoebae, ciliates, rotifers, colorless flagellates, cyanobacteria and algae were found and the most important 45 species were figured in a plate together with saprobiological information for each species. Biota of the inflowing water is usually restricted to bacteria, ciliata and colorless flagellata while the organisms found in outflowing water as well as in periphyton growing on outflow structures indicate 2-3 levels better quality.
Removal of Salmonella and microbial indicators in constructed wetlands treating swine wastewater
Authors: Hill V.R. , Sobsey M.D.
Published: May 2018

Reductions of Salmonella bacteria and enteric microbial indicator organisms were measured in swine wastewater treated by a field-scale surface flow (SF) constructed wetland at a commercial hog nursery in North Carolina and in laboratory-scale SF and subsurface flow (SSF) constructed wetland reactors. Overall reductions of Salmonella, fecal coliforms and E. coli were 96, 98 and 99%, respectively, in the two-cell field-scale wetland. Somatic and F-specific coliphage viral indicators were reduced by 99 and 98%, respectively. Reductions of Salmonella, fecal coliforms and E. coli were similar in the first cell of the field system and in the laboratory-scale SF wetland operated at a TKN loading of 25 kg ha-1 d-1 and 30°C (approximately 70, 90 and 90%, respectively). In the SSF wetland reactor, Salmonella and fecal coliform reductions were 80 and 98%, respectively, at a 40 kg TKN ha-1 d-1 loading and 99.8 and 99.99%, respectively, at a 10 kg TKN ha-1 d-1 loading. These results show that SF constructed wetlands can be effective for reducing enteric pathogens in swine wastewater and that greater removals can be achieved using SSF designs and lower TKN loading rates.
Modelling nitrogen transformations in surface flow wastewater treatment wetlands in Sweden
Authors: Kallner S. , Wittgren H.B.
Published: May 2018

The purpose of this study was to describe and compare the fate of nitrogen (N) in two Swedish wastewater treatment wetlands in the cities of Oxelösund and Hässleholm. Specifically, we wanted to see if a fairly simple model, developed with regard to common data availability, could satisfactorily describe the concentration dynamics at the outlet from the wetlands. A first-order area-based model, with two alternative expressions for temperature dependence, was set up to describe three major processes: ammonification, nitrification and denitrification. The N concentration dynamics at the outlet of the Oxelösund wetland was not satisfactorily described, R2(NH4+-N)=0.33 and R2(NO3--N)=0.10, while the modelled concentrations corresponded quite well with measured concentrations in the Hässleholm wetland, R2(NH4+-N)=0.83 and R2(NO3--N)=0.58. The NO3--N concentrations, in both wetlands, could be slightly better described when introducing a temperature coefficient as an additional free parameter. The explained variances reported above were achieved when the model was calibrated individually for the two wetlands, when the resulting (optimised) reaction rate coefficients for each of the three processes were quite different between the two wetlands. To improve model performance, the rate equations may have to be changed to include factors in addition to concentration and temperature, such as dissolved oxygen and hydraulic efficiency. It may also be important to include other processes, such as plant uptake/decay and ammonia volatilisation.
Development of a conceptual model for vertical flow wetland metabolism
Authors: Giraldo E. , Zárate E.
Published: May 2018

Four parallel vertical constructed wetlands, with a total area of 556 m2, are used to treat domestic wastewater, coming from a community of 550 inhabitants. The system includes pre-treatment with an anaerobic filter and post-treatment with chlorine, before discharging the effluent to the ocean. Four native species of macrophytes were planted: Paspalum penisetum, Typha sp, Conocarpres erectus and Scirpus lacustris. In situ measurements of gas content were performed for each bed during an operation cycle. After a feeding discharge, an unaltered sample of sand from each bed was taken, and a respirometric test was implemented to measure the metabolic activity in terms of oxygen consumption kinetics, CO2 production and organic matter degradation. The results were used to develop a conceptual model of the microbiologic metabolism for the process of organic matter removal from wastewater. Sorption in the bed is the main mechanism for organic matter removal from the wastewater, with subsequent biological oxidation during the resting period. The degradation rate for dissolved organic matter is found to be dependent on its concentration and on oxygen content in the gaseous phase. During the days of major activity, the oxygen content was not fully recovered when a new discharge occurred, finding anaerobic activity within the bed.
Performance of two macrophyte species in experimental wetlands receiving variable loads of anaerobically treated municipal wastewater
Authors: da Motta Marques D.M.L. , Leite G.R. , Giovannini S.G.T.
Published: May 2018

Two highly productive emergent macrophytes, Zizaniopsis bonariensis and Typha subulata were established in experimental subsurface flow, sand-based wetlands receiving anaerobically treated municipal wastewater. The hydraulic loading rate was tested in two levels, sequentially, 6.8 cm.d-1 and 13.6 cm. d-1, for 70 days each. In the 13.6 cm. d-1-loading treatment, among all monitored variables only COD, PO4-Total-P, and Turbidity were removed more efficiently by the planted beds in comparison to unplanted sand beds (P<0.001). When the 6.7 cm. d-1-loading rate was applied no significant improvement in removal was found comparing macrophyte beds to unplanted sand beds, except for PO4-P. T. subulata beds were significantly more efficient than Z.bonariensis beds for most of the variables. The highest significant differences (P<0.001) were related to the main effect of the factor hydraulic loading rate, with decreased removal for increased load when considering the variables Total Coliforms (99.4% to 87.7%), Fecal Coliforms (100% to 89.7%), NH3-N (95.8% to 55.2%), NO3--N (-54% to -396%), Total-N (90.4% to 59.6%), and TSS (86.1% to 46.1%). The performance similarity of planted and unplanted wetland beds in the lower loading condition, except for PO4-P, indicates that plants may not be needed under low loading. However aquatic macrophytes improved wetland efficiency under high loading.