bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal environments of subsurface treatment wetlands
Authors: Kadlec R.H.
Published: May 2018

Treatment wetlands are solar powered ecosystems, resulting in annually cyclic temperatures. This paper reports data and models for temperatures and energy flows for subsurface flow wetlands. The water temperature seasonal cycle follows the air temperature during unfrozen conditions, with small hysteresis. Winter under-ice water temperatures are approximately 2°C. The energy balance is dominated by radiation to and from the wetland, and evaporative losses. Sensible heat flows, conduction and convection are of smaller magnitude. Lateral energy losses were measured to be small. Vertical gains and losses were also small, but of importance in winter conditions. A simple model for ice formation shows that ice formation may be held to an acceptable minimum by addition of mulch or by early snow accumulation.
Determining ecologically acceptable nutrient loads to natural wetlands for water quality improvement
Authors: Keenan L.W. , Lowe E.F.
Published: May 2018

Natural wetlands often function as nutrient sinks, reducing nutrient inputs into lakes and streams. P loading from anthropogenic sources has significantly affected many natural wetlands. This paper describes a method to determine an acceptable P load to natural wetlands based on ecological principles. This approach can be used to determine how much P can be assimilated without diminishing species diversity and, thereby, sets a limit for cultural eutrophication of natural wetlands. The basis for determining an acceptable load is management of risk to species diversity by determination of the maximum area of a wetland that can be put at risk while preserving biodiversity of the overall wetland system. Two cases are distinguished: 1) simple-stress, where growth of the affected area immediately increases risks for species loss, and 2) subsidy-stress, where growth of the affected area first benefits then diminishes net species diversity.
Surmounting the engineering challenges of Everglades restoration
Authors: Goforth G.F.
Published: May 2018

The South Florida Water Management District, in partnership with other agencies and stakeholders, is undertaking one of the world's largest ecosystem restoration programs. The foundation of the nutrient control program for the Everglades is a set of six large constructed wetlands, referred to as Stormwater Treatment Areas (STAs). The initial treatment goal is to reduce phosphorus entering the Everglades to 50 parts per billion. The STAs comprise almost 17,000 hectares, with a capital cost of approximately $700 million. Approximately 4,720 hectares are currently operational, another 2,600 hectares are in the start-up phase, and construction is just getting under way on the remaining areas.

Throughout the design process, engineers and scientists collaborated to capture the best available information on wetland treatment systems, and to develop the most appropriate design criteria. Some of the more challenging issues included characterizing stormwater inflows and phosphorus loads, determining appropriate nutrient removal performance characteristics, and estimating hydraulic design parameters relating to densely vegetated systems.

The design process combined in-house staff with engineering consultants, construction contractors, external review groups and independent peer-review. This paper summarizes major design aspects and key assumptions, and sets the stage for addressing future challenges associated with achieving long-term water quality goals of Everglades restoration.
Changes in plant biomass and nutrient removal over 3 years in a constructed wetland in Cairns, Australia
Authors: Greenaway M. , Woolley A.
Published: May 2018

The surface flow wetland in Cairns, Australia consists of 3 linear channels each 65 m long. Channels 1 and 2 are 5 m wide and Channel 3 is 15 m wide. The wetland was constructed in 1994 and band planted with emergent macrophyte species and alternating open water sections. The wetland was monitored for plant growth and nutrient removal until 1997. During that period HRT was 16 days in Channel 1 and 10 days in Channels 2 and 3; mass loading rates were 2.4 kg Total N and 2.0 kg Total P ha-1 d-1 in Channel 1 and 3.7 kg TN and 3.3 kg TP ha-1 d-1 in Channels 2 and 3. The aim of this work was to determine the proportion of nutrient removal that could be attributed to direct uptake by macrophytes and incorporated into plant biomass. Over the 3 year monitoring period reduction in total mass of nutrients was: Channel 1: 26% P, 85% N; Channel 2: 28% P, 87% N; Channel 3: 21% P, 81% N. Percentage reduction of FRP (Filterable Reactive Phosphorus) was similar to TP; NOx removal was 97-98%. Mass removal rates for TN and TP were higher in Channels 2 and 3 despite greater nutrient loading rates and shorter detention times. Total FRP removal was 23 kg P in Channel 1, 33 kg P in Channel 2 and 70 kg P in Channel 3 of which plant biomass accounted for 65%, 44% and 47% respectively. Total nitrogen removal was 92 kg in Channel 1, 154 kg in Channel 2 and 386 kg in Channel 3 of which plant biomass accounted for 47%, 27% and 27% respectively. Thus, in this tropical surface flow wetland supporting a mixture of emergent macrophytes and floating duckweed, vegetation is an important mechanism for direct nutrient removal.
Constructed wetlands for wastewater treatment in central Italy
Authors: Conte G. , Matinuzzi N. , Giovannelli L. , Pucci B. , Masi F.
Published: May 2018

The performance of 4 constructed wetlands designed by IRIDRA Srl and operating in Tuscany (central Italy) has been monitored during the last three years. The 4 treatment systems have different sizes and characteristics: one single stage secondary treatment (150 p.e.); two secondary treatment plants with effluent reuse: one small (60 p.e) and the other big (350 p.e.); a tertiary treatment of effluents from an activated sludge plant with high hydraulic load fluctuation (5-500 p.e.). Due to geographical and economic constraints the four systems have high hydraulic and organic loading rates, neverthless the systems show very good removal performance of COD (62-95%), especially the ones with higher inflow COD concentrations (87-95%). Interesting results concerning also removal percentage of MBAS (42-88%) and ammonium (42-85%) were obtained, even though NH4+ concentration in the outflows of some of the plants, doesn't always comply with Italian quality standards.
On-site domestic wastewater treatment by reed bed in the moist subtropics
Authors: Davison L. , Headley T. , Edmonds M.
Published: May 2018

This paper summarises the results of studies on four subsurface flow wetlands (reed beds) located in the moist sub-tropical north eastern corner of the Australian state of New South Wales. The reed beds, which are subjected to a variety of effluent types, all have a gravel substrate planted with Phragmites australis. All four units were found to maintain satisfactory treatment performance year round. Mean removal efficiencies ranged from 56% to 90% (SS), 70% to 93% (BOD), 38% to 66% (TN), 87% to 99.8% (Faecal coliforms), and 42% to 70% (TP - with one seasonal result of 0% for the eight year old unit) for the four reed beds. After eight years in operation the oldest reed bed was showing signs of phosphorus saturation with outlet TP concentrations exceeding inlet concentrations on some occasions. The youngest reed bed studied appeared to be operating efficiently after five months. A summer water balance on one of the reed beds revealed an average crop factor of 1.6 and a moisture loss to atmosphere of 40% of influent flow. Treatment performance (particularly for TN and SS) was found to be negatively correlated with rainfall during one study. The paper discusses the implications of the above results for on-site system designers and regulators and identifies areas for further investigation.
Experimental results on constructed wetland pilot system
Authors: González J.M. , Ansola G. , Luis E.
Published: May 2018

Research into a constructed wetland for wastewater treatment using M.H.E.A. (Hierarchical Mosaic of Artificial Ecosystems) pilot system was carried out over a vegetative period in 8 different flow and vegetable composition series. The system consisted of a free water pond as a first step working as primary treatment followed by a zone with Typha sp. and surface flow and finally a woody zone with a subsurface flow and planted with ligneous species (Salix sp., Populus sp., Fraxinus sp. and Alnus sp.).

Removal efficiency in the study reflects an optimal result: 80-99% total suspended matter removal, 82-98% organic matter removal, 70-98% nutrients removal and up to 99.9% faecal bacterial disinfecting. Effluent characteristics were in accordance with European Union legislation criteria for wastewater treatment systems.
Reed beds: constructed wetlands for municipal wastewater treatment plant sludge dewatering
Authors: Begg J.S. , Lavigne R.L. , Veneman P.L.M.
Published: May 2018

Reed beds are an alternative technology wastewater treatment system that mimic the biogeochemical processes inherent in natural wetlands. The purpose of this project was to determine the effectiveness of a reed bed sludge treatment system (RBSTS) in southern New England after a six-year period of operation by examining the concentrations of selected metals in the reed bed sludge biomass and by determining the fate of solids and selected nutrients. Parameters assessed in both the reed bed influent and effluent: total suspended solids, biochemical oxygen demand, nitrate-nitrogen and total phosphorus. In addition, the following metals were studied in the reed bed influent, effluent and Phragmites plant tissue and the sludge core biomass: boron, cadmium, chromium, copper, iron, lead, manganese, molybdenum, nickel, and zinc. The removal efficiencies for sludge dewatering, total suspended solids and biochemical oxygen demand were all over 90%. Nitrate and total phosphorus removal rates were 90% and 80% respectively. Overall metals removal efficient was 87%. Copper was the only metal in the sludge biomass that exceeded the standards set by the Massachusetts Department of Environmental Protection for land disposal of sludge. The highest metal concentrations, for the most part, tended to be in the lower tier of the sludge profile. The exception was boron, which was more concentrated in the middle tier of the sludge profile. The data and results presented in this paper support the notion that reed bed sludge treatment systems and the use of reed beds provide an efficient and cost effective alternative for municipal sludge treatment.
Zero-discharge of nutrients and water in a willow dominated constructed wetland
Authors: Gregersen P. , Brix H.
Published: May 2018

A novel constructed wetland system has been developed to treat sewage, evaporate water and recycle nutrients from single households at sites where effluent standards are stringent and soil infiltration is not possible. Main attributes of the willow wastewater cleaning facilities are that the systems have zero discharge, the willows evapotranspire the water, and nutrients can be recycled via the willow biomass produced in the system. The willow wastewater cleaning facilities generally consist of c. 1.5 m deep high-density polyethylene-lined basins filled with soil and planted with clones of willow (Salix viminalis L.). The surface area of the systems depends on the amount and quality of the sewage to be treated and the local annual rainfall. For a single household the area needed typically is between 200-300 m2. Settled sewage is dispersed underground into the bed under pressure. When correctly dimensioned, the willow will - on an annual basis - evapotranspire all water from the sewage and rain falling onto the system, and take up all nutrients and heavy metals from the sewage. The stems of the willows are harvested on a regular basis to remove nutrients and heavy metals and to stimulate the growth of the willows. Initial experiences from full-scale systems in Denmark show promising results.
Diel changes in iron concentrations in surface-flow constructed wetlands
Authors: Goulet R.R. , Pick F.R.
Published: May 2018

Diel changes in Fe concentrations were examined from spring to late fall at two surface-flow wetlands. The highest concentrations of ferrous, dissolved and total Fe were measured at night in the littoral zone, when oxygen and pH were low. The lowest Fe concentrations were measured during the day when oxygen and pH were highest. The amplitude of change over the day-night cycle was greatest in July and lowest in May and October. These diel changes were also observed at the outlet of both wetlands. Overall, O2 and pH explained 60% of the observed seasonal and diel variation in water Fe (R2=0.60, p=0.004). The treatment performance of wetlands can be overestimated when based on samples collected during the day.
Wastewater treatment by algal turf scrubbing
Authors: Craggs R.L.
Published: May 2018

Algal turf scrubbing (ATS) is a novel wetland technology that has been designed and engineered to promote natural wastewater treatment processes. Algal turf scrubbing improves water quality by passing a shallow stream of wastewater over the surface of a gently sloped floway. The floway is colonised by a natural heterogeneous assemblage of periphyton consisting of cyanobacteria, filamentous algae and epiphytic diatoms together with aerobic bacteria and fungi. Algal photosynthesis provides oxygen for aerobic breakdown of wastewater by heterotrophic bacteria. Pollutants are extracted from the wastewater by several processes including assimilation, adsorption, filtration and precipitation. The algal turf is harvested periodically to remove the accumulated periphyton biomass and associated pollutants from the system. This paper will present results from a demonstration ATS facility in Patterson, California which was used to polish secondarily treated wastewater. The design and operational factors that influence the treatment performance of ATS systems is discussed. Results indicate the potential of the ATS for nutrient removal from secondarily treated wastewater and agricultural drainage waters.
Retention of selected heavy metals: Cd, Cu, Pb in a hybrid wetland system
Authors: Obarska-Pempkowiak H.
Published: May 2018

The budget of heavy metals was investigated in a constructed wetland in a hybrid wetland system near Gdan«sk. It is a pilot wastewater treatment plant (WWTP) designed for 150 PE (person equivalent). The system consists of two sections: a vegetated submerged bed (VSB) with horizontal flow of sewage and a cascade filter situated on a slope of a hill. Total area of the constructed wetland is about 870 m2. Domestic sewage, after a conventional pretreatment (consisting of an Imhoff tank and a trickling filter) is pumped to the VSB filter located on the top of the hill and then flows through subsequent segments of the constructed wetland. In the period 1995-98 the measurements of several heavy metals (Cd, Cu, Pb) were carried out in sewage inflowing, outflowing and collected from the in between sections of the system. Moreover analysis of sediment collected in ditches of the cascade filter, VSB filter and reed were carried out. The content of heavy metals in suspended solids decreased along the course of treatment, starting from VSB filter, through the first ditch to the last ditch. Measurable concentrations of dissolved heavy metals were found in sewage collected from several subsequent ditches. Sorption was deemed the main mechanism of dissolved metals removal in subsequent ditches.
Treatment of swine wastewater in marsh-pond-marsh constructed wetlands
Authors: Reddy G.B. , Hunt P.G. , Phillips R. , Stone K. , Grubbs A.
Published: May 2018

Swine waste is commonly treated in the USA by flushing into an anaerobic lagoon and subsequently applying to land. This natural system type of application has been part of agricultural practice for many years. However, it is currently under scrutiny by regulators. An alternate natural system technology to treat swine wastewater may be constructed wetland. For this study we used four wetland cells (11 m width × 40 m length) with a marsh-pond-marsh design. The marsh sections were planted to cattail (Typha latifolia, L.) and bulrushes (Scirpus americanus). Two cells were loaded with 16 kg N ha-1 day-1 with a detention of 21 days. They removed 51% of the added N. Two additional cells were loaded with 32 kg ha-1 day-1 with 10.5 days detention. These cells removed only 37% of the added N. However, treatment operations included cold months in which treatment was much less efficient. Removal of N was moderately correlated with the temperature. During the warmer periods removal efficiencies were more consistent with the high removal rates reported for continuous marsh systems - often > than 70%. Phosphorus removal ranged from 30 to 45%. Aquatic macrophytes (plants and floating) assimilated about 320 and 35 kg ha-1, respectively of N and P.
Reed bed dewatering of agricultural sludges and slurries
Authors: Edwards J.K. , Gray K.R. , Cooper D.J. , Biddlestone A.J. , Willoughby N.
Published: May 2018

In trials at Rugeley, UK, reed beds were used for dewatering agricultural sludges and slurries. Three beds, each of 3.5m2, were employed, two planted with Phragmites australis, the third left unplanted as control. The sludge contained partly oxidised solids from a Biological Aerated Filter (BAF) treating weak pig slurry. It was supplemented with untreated settled pig slurry. Following reed establishment planted Bed A was fed at a constant similar rate to the unplanted Control Bed C. The second planted Bed B was fed at higher rates alternating with rest periods. On this bed the aeration pipes were blocked off. The trials were run for 16 months, which included two summer periods. The results showed that the planted Bed A had definitely better dewatering ability than the unplanted one fed at a similar rate. During the summer months Bed B could be fed at over twice the rate used for the constant input beds. The percolate from the control bed was more highly oxidised than from the planted beds, probably due to a longer holdup time in the absence of reeds. On Bed B the reed quality deteriorated during the second year, after use of untreated slurry as feed.
Using wetlands for water quality improvement in agricultural watersheds; the importance of a watershed scale approach
Authors: Crumpton W.G.
Published: May 2018

Agricultural applications of fertilizers and pesticides have increased dramatically since the middle 1960s, and agrochemical contamination of surface and groundwater has become a serious environmental concern. Since the mid-1980s, a variety of state and federal programs have been used to promote wetland restoration, and these continuing efforts provide a unique opportunity for water quality improvement in agricultural watersheds. However, wetland restorations have been motivated primarily by concern over waterfowl habitat loss, and model simulations suggest that commonly used site selection criteria for wetland restorations may be inadequate for water quality purposes. This does not lessen the promise of wetlands for water quality improvement in agricultural watersheds, but rather emphasizes the need for watershed scale approaches to wetland siting and design. Water quality is best viewed from a watershed perspective, and watershed scale endpoints should be explicitly considered in site selection for wetland restoration.
Removal of bacterial and viral faecal indicator organisms in a waste stabilization pond system in Choconta, Cundinamarca (Colombia)
Authors: Campos C. , Guerrero A. , Cárdenas M.
Published: May 2018

A major objective for domestic wastewater treatment using waste stabilization pond systems is the removal of pathogenic microorganisms. Traditional evaluation parameters for faecal contamination are the total and faecal coliforms. However, epidemiological studies, environmental resistance and the behaviour in the treatment systems, show that viruses are an important disease agent and even more resistant to disinfection than bacteria. Therefore, it is important to introduce viruses as a faecal indicator and to compare them with the traditional bacterial indicators. A waste stabilization pond system was evaluated in the municipality of Chocontá, Cundinamarca (Colombia), for the removal of faecal indicators (such as Escherichia coli, Streptococcus faecalis, Clostridium perfringens) and viruses like F+, somatic and Bacteroides fragilis phages. The system includes two facultative ponds in series with a flow of 1555 m3/day. Samples were collected at the entrance of the system, in the two ponds and from the final effluent. Results show a decrease between 0.3 and 4.7 logarithmic units in the bacterial indicators and between 1 and 4.6 logarithmic units with viral indicators.
Effect of anaerobic pretreatment on environmental and physicochemical characteristics of duckweed based stabilization ponds
Authors: Caicedo J.R. , Espinosa C. , Andrade M. , Gijzen H.
Published: May 2018

Duckweed based stabilization ponds, an alternative for wastewater treatment, are attracting a growing interest from researchers because they are basically a low cost technology, easy to built and operate, and produce tertiary quality effluents. Besides, this technology offers the possibility of resource recovery by producing high quality duckweed protein, which can be of further use. Since the technology is rather new, there are many aspects to be studied before its full-scale implementation. It is necessary to gain sound knowledge of the basic principles of the complex processes occurring in the system, as well as of the practical aspects of design and operation. The presence of a layer of duckweed on the surface is expected to produce different environmental and physicochemical conditions in the water from those found in conventional stabilization ponds. These environmental and physicochemical conditions affect both plant growth and biological treatment processes in the system, therefore it is important to determine their behavior in a duckweed system and how they can be affected by an anaerobic pretreatment. Continuous flow pilot plants composed of seven ponds in series were operated with artificial substrate under two different conditions: with anaerobic pretreatment and without anaerobic pretreatment. The flow was kept constant during the operation. Conditions such as pH, temperature, dissolved oxygen, alkalinity, conductivity, chemical oxygen demand, biochemical oxygen demand, total and ammonium nitrogen, nitrites and nitrates, and phosphorus were evaluated in the system under steady state conditions. The main conclusions from the study include the following: pH, temperature and oxygen profiles are more stable in duckweed ponds than in conventional stabilization ponds; anaerobic pretreatment has a significant effect on the oxygen concentration in the system and on the organic matter removal but not on the nutrient removal.
The potential for water hyacinth to improve the quality of Bogota River water in the Muña Reservoir: comparison with the performance of waste stabilization ponds
Authors: Giraldo E. , Garzón A.
Published: May 2018

The potential application of Water Hyacinth (Eichhornia crassipes) in organic matter degradation, sedimentation, nutrient and heavy metal absorption and sulfur reduction in the Muña Reservoir has been tested in experimental lagoons. The lagoons were operated at hydraulic retention times (HRT) of 6, 9 and 15 days. One lagoon was covered with Water Hyacinth, which is naturally growing in the Muña Reservoir, while another lagoon was operated as a conventional oxidation pond. The Water Hyacinth lagoon had better removal efficiencies for almost all parameters measured: BOD5, total suspended solids, COD, nitrogen, phosphorus and heavy metals. The oxidation lagoon was facultative for HRT of 9 and 15 days, and anoxic when operated at 6 days HRT. At HRT of 15 days the water quality in the effluent of the covered lagoon corresponded to 12 mg/l of BOD, 6 mg/l of suspended solids and 0.8 mg/l of hydrogen sulfide. Hydrogen sulfide levels in the Muña reservoir can be substantially reduced at HRT higher than 15 days in both lagoons. The uncovered lagoon had better hydrogen sulfide removal during the day but presents high levels at night. If the hydraulic retention time in the Muña reservoir is increased, the water quality of the Bogota river can be substantially improved for all the HRTs tested in the pilot units. HRT seems to give a better prediction of overall effluent water quality than surface loading. More research is needed in order to define the optimum water hyacinth density in the Muña reservoir to determine its influence on the water quality of the effluent. The influence is expected to be negative due to an internal increase of BOD, solids, nutrients and metals loads due to plant decay.
Comparison of conventional and macrophyte-based systems for the treatment of domestic wastewater
Authors: Baldizón M.E. , Dolmus R. , Quintana J. , Navarro Y. , Donze M.
Published: May 2018

Different wetland and stabilisation ponds, comprising of duckweed, reed and algal systems, were compared for the treatment of domestic sewage. Within the large performance variations observed within systems, the differences observed between systems can be considered to be insignificant.
Effects on crops of irrigation with treated municipal wastewaters
Authors: Fasciolo G.E. , Meca M.I. , Gabriel E. , Morábito J.
Published: May 2018

The fertilizing potential of treated municipal wastewater (oxidation ditch) and crop sanitary acceptability for direct human consumption were evaluated in Mendoza, Argentina. Two experiments were performed on a pilot plot planted with garlic (1998) and onions (1999) using furrow irrigation with three types of water in 10 random blocks: treated effluent (2.5 × 103 MPN Escherichia coli/100ml, 3 helminth eggs/l, and Salmonella (positive); and well water (free of microorganisms), with and without fertilizer. Two responses were evaluated: (1) crop yield, and (2) crop microbiological quality for human consumption at different times after harvest. Crop yields were compared using Variance analysis. Crops' sanitary acceptability was assessed using a two-class sampling program for Salmonella (n=10; c=0), and a three-class program for E. coli (n=5, c=2, M=103 and m=10 MPN/g) as proposed by the International Commission on Microbiological Specifications for Foods (ICMSF) for fresh vegetables. Wastewater irrigation acted as well water with fertilizer, increasing garlic and onion yields by 10% and 15%, respectively, compared to irrigation with well water with no fertilizer. Wastewater-irrigated garlic reached sanitary acceptability 90 days after harvest, once attached roots and soil were removed. Onions, which were cleaned immediately after harvest, met this qualification earlier than garlic (55 days). Neither the wastewater-irrigated crops nor the control crops were microbiologically acceptable for consumption raw at harvest.
Microbiological quality of a waste stabilization pond effluent used for restricted irrigation in Valle Del Cauca, Colombia
Authors: Madera C.A. , Peña M.R. , Mara D.D.
Published: May 2018

This paper discusses the applicability of effluent reuse in agriculture after treatment in a series of anaerobic, facultative and maturation ponds. The WSP system is located in Ginebra municipality, a small town in southwest Colombia. The total HRT is 12 days. Several samples of the final effluent were taken over a 55 day period and were analysed for E.coli, Streptococcus spp. and helminth eggs. Some additional grab samples were taken to determine the presence of pathogenic bacteria such as Salmonella spp. and Shigella spp. The results showed that the system was able to remove 4 log units of E.coli, 1 log unit of Streptococcus spp. and 100% of helminth eggs. Meanwhile, Salmonella spp. were detected in the effluent of the facultative pond whilst Shigella spp. were not detected in any sample. The main species of helminth eggs encountered were Taenia spp., Ascaris spp., Trichuris spp., Hymenolepis nana, H. diminuta and Enterobius vermicularis. Removal efficiencies were satisfactory despite the relatively short HRT. Nevertheless, WHO guidelines were slightly surpassed in the case of E.coli for unrestricted irrigation. The helminth egg value was always below the maximum WHO limit. Hence, this effluent can be safely used for restricted irrigation provided that field workers are protected from direct contact with wastewater given the presence of Salmonella spp. in the facultative pond effluent.
Tipping bucket mechanical errors and their influence on rainfall statistics and extremes
Authors: La Barbera P. , Lanza L.G. , Stagi L.
Published: May 2018

Based on the error figures obtained after laboratory tests over a wide set of operational rain gauges from the network of the Liguria region, the bias introduced by systematic mechanical errors of tipping bucket rain gauges in the estimation of return periods and other statistics of rainfall extremes is quantified. An equivalent sample size is defined as a simple index that can be easily employed by practitioner engineers to measure the influence of systematic mechanical errors on common hydrological practice and the derived hydraulic engineering design. A few consequences of the presented results are discussed, with reference to data set reconstruction issues and the risk of introducing artificial climate trends in the observed rain records.
100 years of Belgian rainfall: are there trends?
Authors: Vaes G. , Willems P. , Berlamont J.
Published: May 2018

In 1999 the digitisation of old rainfall records of measurements at Uccle (Belgium) was completed, which resulted in a unique rainfall series of 100 years (period 1898-1997). This is an ideal opportunity to search for trends in the rainfall over the last century. Large variations in rainfall probability over the century have been observed. For small aggregation levels there is a small decrease in extreme rainfall events over the century. For large aggregation levels there is a more explicit increase in extreme rainfall. Because the rainfall on seasonal aggregation level is only slightly increased, the increase in extreme rainfall events for aggregation levels between a few days and a few months can only occur due to larger clustering. However, the final conclusion is that no significant trend can be observed. A pure random variation of the rainfall can cause equally large variations. This does not exclude a possible trend in flooding frequency, due to the strong increase in urbanisation over the last century.
Evaluation of an artificial neural network rainfall disaggregation model
Authors: Burian S.J. , Durrans S.R.
Published: May 2018

Previous research produced an artificial neural network (ANN) temporal rainfall disaggregation model. After proper training the model can disaggregate hourly rainfall records into sub-hourly time increments. In this paper we present results from continued evaluations of the performance of the ANN model specifically examining how the errors in the disaggregated rainfall hyetograph translate to errors in the prediction of the runoff hydrograph. Using a rainfall-runoff model of a hypothetical watershed we compare the runoff hydrographs produced by the ANN-predicted 15-minute increment rainfall pattern to runoff hydrographs produced by (1) the observed 15-minute increment rainfall pattern, (2) the observed hourly-increment rainfall pattern, and (3) the 15-minute increment rainfall pattern produced by a disaggregation model based on geometric similarity. For 98 test storms the peak discharges produced by the ANN model rainfall pattern had a median under-prediction of 16.6%. This relative error was less than the median under-prediction in peak discharge when using the observed 15-minute rainfall patterns aggregated to hourly increments (40.8%), and when using rainfall patterns produced by the geometric similarity rainfall disaggregation model (21.9%).
Integrated urban drainage, status and perspectives
Authors: Harremös P.
Published: May 2018

This paper summarises the status of urban storm drainage as an integrated professional discipline, including the management-policy interface, by which the goals of society are implemented. The paper assesses the development of the discipline since the INTERURBA conference in 1992 and includes aspects of the papers presented at the INTERURBA-II conference in 2001 and the discussions during the conference. Tools for integrated analysis have been developed, but there is less implementation than could be expected. That is due to lack of adequate knowledge about important mechanisms, coupled with a significant conservatism in the business. However, significant integrated analyses have been reported. Most of them deal with the sewer system and the treatment plant, while few incorporate the receiving water as anything but the object of the loads to be minimised by engineering measures up-stream. Important measures are local infiltration, source control, storage basins, local treatment and real time control. New paradigms have been introduced: risk of pollution due to system failure, technology for water reuse, sustainability, new architecture and greener up-stream solutions as opposed to down-stream concrete solutions. The challenge is to combine the inherited approaches with the new approaches by flexibility and adaptability.
Management of sensible water uses with real-time measurements
Authors: Fleischmann N. , Staubmann K. , Langergraber G.
Published: May 2018

For the protection of bankside wells and a groundwater recharge an early warning system had to be developed. The monitoring network design is based on sensor measurements only. For this purpose a new submersible spectrometer has been successfully tested for multi-parameter measurements directly in the medium. The developed system can easily be upgraded with other new sensors. Only calibration and validation data are supplied by conventional grab sampling and laboratory analysis.. A conventional testfilter improved by on-line monitoring at 5 sampling sites serves as a reference system. The whole system is equipped with remote control and the internet serves as the control centre of the network. All measurement data from all 9 sites are available in real time on the internet.
Fate of pharmaceuticals during indirect potable reuse
Authors: Drewes J.E. , Heberer T. , Reddersen K.
Published: May 2018

The scope of this study was directed to examine different wastewater treatment technologies (activated sludge, trickling filter, nanofiltration, reverse osmosis) at full-scale facilities in Arizona and California leading to indirect potable reuse and their capability to remove pharmaceuticals. Additionally, the fate of selected pharmaceuticals was studied during soil-aquifer treatment (SAT) at sites where secondary and tertiary treated effluents are used for subsequent groundwater recharge. Facilities employing longer detention times during treatment (nitrifying and denitrifying plants) showed significant lower effluent concentration for analgesic drugs as compared to trickling filter or activated sludge facilities applying shorter detention times. A similar trend was observed for the lipid regulator gemfibrozil, which was significantly removed in denitrified effluents, whereas a trickling filter treated effluent exhibited concentration of 1,235 ng/L. Antiepileptic drugs, such as carbamazepine and primidone, showed no dependency on the wastewater treatment applied. None of the investigated drugs was detected in tertiary treated effluents after nanofiltration or reverse osmosis. After SAT, analgesic/anti-inflammatory drugs were efficiently removed after retention times of less than 6 months and remaining concentrations were near or below the detection limit of the analytical method. A high potential for biodegradation was also observed for anti-inflammatory drugs in groundwater recharge systems. The antiepileptics carbamazepine and primidone represented the most dominant of all investigated drugs in well treated domestic effluents (nitrifying/denitrifying plants). Removal of carbamazepine and primidone did not seem to occur during travel times of more than 6 years in the subsurface.
A broad spectrum analytical scheme for the screening of endocrine disruptors (EDs), pharmaceuticals and personal care products in wastewaters and natural waters
Authors: Bruchet A. , Prompsy C. , Filippi G. , Souali A.
Published: May 2018

This paper describes the implementation of a broad-spectrum analytical scheme which was used at three wastewater plants for the screening of organic micropollutants. The more than 200 compounds identified comprised a variety of endocrine disrupters, pharmaceutical compounds and personal care products. Glycol ethers which have well established effects on the development of the embryo were outstanding in all plants investigated. The first plant, which was investigated at various stages of treatment, was quite efficient at removing undesirable compounds. The second plant, which received 50% of effluents from pharmaceutical industries, released low but significant levels of drugs. An antibiotic, cyclamidomycine, was identified in the effluent from the third plant.
Virus removal by soil passage at field scale and ground-water protection of sandy aquifers
Authors: Schijven J.F. , Hassanizadeh S.M.
Published: May 2018

Virus removal from groundwater by soil passage often appears to be much higher during the first few metres due to the presence of more favorable sites for attachment than thereafter. A model is presented which interprets virus removal as a function of collision efficiencies αbeta; and αλl, inactivation rate coefficient μll and rate parameter γ. Initial high removal is determined by αβ, which decreases exponentially at a rate γ to a constant base removal rate that is determined by αλ and μl.

A hypothetical worst case was simulated to calculate the travel distance and time required for 9 log10 protection against virus contamination of groundwater wells in anoxic sandy aquifers. Unfavorable conditions for attachment were assumed. Virus was constantly leaking from a sewage pipe lying at the groundwater table. Mixing reduced virus concentration by 3.1 to 4.0 log10. For an additional 5.0 to 5.9 log10 protection against virus contamination by attachment and inactivation, residence times of about three to seven times longer than the current guideline of 60 days are needed, depending on abstraction rates, aquifer thickness and grain size of the sand.
Particle transport in a karst aquifer: natural and artificial tracer experiments with bacteria, bacteriophages and microspheres
Authors: Auckenthaler A. , Raso G. , Huggenberger P.
Published: May 2018

Fast changes in spring water quality in karst areas are a major concern for production of drinking water and require detailed knowledge of the complex interaction between karst aquifer, transport behavior of microorganisms and water treatment. We have conducted artificial and natural particle transport experiments at a karst spring with bacteria, bacteriophages, microspheres, and pathogens. Transport of the investigated microorganisms, turbid matter and chemical pullutants as well as increase in discharge are strongly related to precipitation and the heterogeneity of the aquifer. The indicator bacteria E. coli revealed a significant correlation to verotoxin-producing E. coli and Cryptosporidium spp. We conclude that artificial particle tracers can help identify “ot spots” for microbial recharge and that system parameters in spring water such as turbidity, UV-extinction and increase in discharge can be key parameters for efficient raw water management.
Modelling the activated sludge flocculation process combining laser light diffraction particle sizing and population balance modelling (PBM)
Authors: Nopens I. , Biggs C.A. , De Clercq B. , Govoreanu R. , Wilén B.-M. , Lant P. , Vanrolleghem P.A.
Published: May 2018

A technique based on laser light diffraction is shown to be successful in collecting on-line experimental data. Time series of floc size distributions (FSD) under different shear rates (G) and calcium additions were collected. The steady state mass mean diameter decreased with increasing shear rate G and increased when calcium additions exceeded 8 mg/l. A so-called population balance model (PBM) was used to describe the experimental data. This kind of model describes both aggregation and breakage through birth and death terms. A discretised PBM was used since analytical solutions of the integro-partial differential equations are non-existing. Despite the complexity of the model, only 2 parameters need to be estimated: the aggregation rate and the breakage rate. The model seems, however, to lack flexibility. Also, the description of the floc size distribution (FSD) in time is not accurate.
Modelling wastewater transformation in sewers based on ASM3
Authors: Huisman J.L. , Gujer W.
Published: May 2018

A deterministic model for wastewater transformations in the sewer that includes activity in the wastewater and in the sewer wall biofilm was developed. It is based on the Activated Sludge Model No. 3 (ASM3). The mass transfer processes in the biofilm were modelled with the effectiveness approach. This approach allowed for fast calculation, required only a limited number of parameters and gave good results. The ASM3 related parameters were calibrated and validated with laboratory experiments. An equation for the aeration of the wastewater through the water surface was determined with a method based on the inert gas sulphur hexafluoride. The other model parameters such as wall roughness, attachment of particles to the biofilm and biofilm erosion were calibrated and validated with field experiments in a main sewer. The resulting model described the oxygen concentration and wastewater respiration well. It can be easily linked for integrated urban hydrology modelling with the WWTP Activated Sludge Model and the newly proposed River Water Quality Model No. 1.
Experience with guidelines for wastewater characterisation in The Netherlands
Authors: Roeleveld P.J. , van Loosdrecht M.C.M.
Published: May 2018

In this paper experiences and results are presented with guidelines for wastewater characterisation that are standardised in the Netherlands for modelling purposes with ASM. The wastewater characterisation is based on a physical-chemical method to characterise the soluble and particulate fractions, combined with a BOD-analysis for characterising the biodegradable fraction of the influent COD. By following the guidelines, a sufficiently detailed and practical characterisation is obtained, and the results can be used for simulation studies on treatment plants for process optimisation, trouble-shooting and design assistance. At present, five years of experience is gained with the guidelines and they were used for the simulation of circa 100 treatment plants. The guidelines are evaluated as simple and easy to implement in routine analysis programs.
Effect of solids retention time and wastewater characteristics on biological phosphorus removal
Authors: Henze M. , Aspregren H. , la Cour Jansen J. , Nielsen P.H. , Lee N.
Published: May 2018

The paper deals with the effect of wastewater, plant design and operation in relation to biological nitrogen and phosphorus removal and the possibilities to model the processes. Two Bio-P pilot plants were operated for 2.5 years in parallel receiving identical wastewater. The plants had SRT of 4 and 21 days, the latter had nitrification and denitrification. The plant with 4 days SRT had much more variable biomass characteristics, than the one with the high SRT. The internal storage compounds, PHA, were affected significantly by the concentration of fatty acids or other easily degradable organics in the wastewater, and less by the plant lay-out. The phosphorus removal is mainly dependent on availability in the wastewater of fatty acids but also by the suspended solids in the effluent, which is higher in the plant with nitrification-denitrification, probably due to a higher SVI or denitrification in the settler. The addition of glucose to the influent seems to have an effect on the performance of the plants similar to that of acetic acid. In spite of great load variations over time to the pilot plants and the different operational modes, the study of population dynamics showed less significant variations with time which has importance in relation to modelling. The overall conclusion of the comparison between the two plants is that the biological phosphorus removal efficiency under practical operating conditions is affected by the SRT in the plant and the wastewater composition. Thus great care should be taken when extrapolating results from one type of plant to another. Indirectly the experiments confirm that results from lab-experiments with artificial wastewater are difficult to extrapolate through modelling to real life wastewater and conditions. The 2.5 years time series can be valuable in verification of models for Nitrogen and Enhanced Biological Phosphorus Removal.
Error diagnostics and data reconciliation for activated sludge modelling using mass balances
Authors: Meijer S.C.F. , van der Spoel H. , Susanti S. , Heijnen J.J. , van Loosdrecht M.C.M.
Published: May 2018

Research on activated sludge models is mainly directed towards the reliability and estimation of model coefficients. Model calculations however, rely heavily on accurate determination of operational conditions. Accurate measurement of operational conditions and mass flows is difficult, caused by large (full-scale) process flows and the absence of reliable measurements. Therefore operational data should be verified on (gross) errors before being implemented in model studies. Calibrating a model on erroneous mass flows leads to laborious calibration procedures and moreover, unjustified adaptation of the model (kinetic and stoichiometric) parameters. Gross error detection is possible when there are more measurements than strictly required to solve a system of linear conservation relations (mass balances). A simple method for error detection is evaluating the mass balance residuals. For over determined systems data accuracy can be improved using balancing methods (i.e. minimising balance residuals). This is referred to as data reconciliation. A reconciled data set contains fewer errors and is exactly in line with the mass balances of the system. In this paper we describe a method for gross error detection and data reconciliation. It is shown how data reconciliation improves the accuracy of the data set and how the use of a balanced data set simplifies the model calibration procedure. This is demonstrated on the basis of a modelling study of a full-scale WWTP.
Experiences with computer simulation at two large wastewater treatment plants in northern Poland
Authors: Makinia J. , Swinarski M. , Dobiegala E.
Published: May 2018

Mathematical modelling and computer simulation have became a useful tool in evaluating the operation of wastewater treatment plants (WWTPs) in terms of nutrient removal capability. In this study, steady-state simulation results for two large biological nutrient removal WWTPs are presented. The plants are located in two neighbouring cities Gdansk and Gdynia in northern Poland. Simulations were performed using a pre-compiled model and layouts (MUCT and Johannesburg processes) implemented in the GPS-X simulation package. The monthly average values of conventional parameters, such as COD, Total Suspended Solids, total N, N-NH4+, P-PO4− were used as input data. The measured effluent concentrations of COD, N-NH4+, N-NO3− and P-PO4− as well as reactor MLSS were compared with model predictions. During calibration, performed from the process engineering perspective, default values of only five model parameters were changed. The opportunities for further applications of such models in municipal WWTPs are discussed.