Simulated storm event flow design and modelling for stormwater treatment studies

Urban stormwater is a major non-point source of aquatic pollution. It is necessary to design and implement pilot experiments to investigate the effect of specific forcing functions under controlled conditions. In this work, a simple storm event inflow is designed to simulate a variable duration storm event using only a pump and mixer. The results indicate that two-phase straight inflow changed to right-skew convex curve after cylinder transformation. The method can be used to rapidly design simulated variable duration storm event flows for pilot studies for researchers, hydrologists and engineers.     

Influence of aging on phosphorus sorption to alum floc in lake water

Alum is often added to eutrophic lakes to limit the release of phosphorus from sediments. This study quantified the effect of age and extent of crystallization on the phosphate (PO4-P) sorption capacity of alum floc. Aluminum hydroxide flocs were formed from alum addition at a dose of 25 mg/L of Al3+ to Big Bear Lake waters returned to the laboratory; flocs were then aged for 4, 20, 50, 120, and 180 days in the treated lake waters. The physical and mineralogical properties of the alum floc were characterized using surface area and thermal analyses. Phosphate sorption to the floc was evaluated using filtered lake water and NaCl/NaHCO3 solutions spiked with PO4-P concentrations ranging from 0 to 100 mg/L. The Langmuir model provided reasonable fits to data (r2 = 0.97-1.00), from which sorption constants and sorption maxima were determined. Phosphate sorption decreased with increased floc age and crystallinity and decreased surface area. Phosphate sorption maximum of the alum floc aged for 6 months was about 50% lower than freshly precipitated floc, while the binding constant, Kads, decreased approximately 65% over this same time period.     

Influence of salinity and mineralization on trace metal sorption to cyanobacteria in natural waters

The equilibrium distribution of Cd, Cu and Pb between the cyanobacterium Anabaena spp. and natural lake water as a function of salinity and degree of algal decomposition, was studied using batch experiments. Adsorption isotherms could be described with the Freundlich equation. Distribution coefficients (K_d) for Anabaena spp. were largest for Pb, followed by Cd and Cu. The variation in K_d values for Cd was explained by a model accounting for metal complexation to the algal surface and complexation by dissolved ligands of variable concentration. The phytoplankton/water distribution of Cd in waters of different salinity appears to be regulated by the free Cd²⁺ activity in solution. Mineralization of Anabaena spp. for 42 d resulted in a decrease of the solid to water ratio by a factor of 12, and an increase in K_d for Cd (factor four), Cu (factor eight) and Pb (factor 10–20). The increase in K_d is attributed to a higher affinity of the metals for the adsorbent. The use of constant K_d values for mineralizing phytoplankton and detritus in trace metal fate models, may result in underestimations of bound fractions. The extent to which this fraction is underestimated, depends on the time course of the distribution coefficient and the solid to water ratio during the mineralization process.     

Distribution of organic pollutants and natural organic matter in urban storm water sediments as a function of grain size

The sealing of surfaces in urban areas makes storm water management compulsory. Contaminated particles carried from urban surfaces are deposited in infiltration ponds. This gives rise to a highly organic (11% DW) contaminated sedimentary layer (Zn:1.2 mg/g, Cd:15 mg/kg) that could threaten groundwater quality. During infiltration, particle arrangement impacts infiltrating water and sediment exchanges. In this context, understanding particle arrangement and leachable components is essential. This study investigates Organic Matter (OM) not only as a pollutant but also as a substrate and a structuring element. The leachable fraction was collected and grain size fractionation was performed. OM of sediments and isolated fractions were characterized by measuring organic carbon content, isolating aromatic hydrocarbons, saturated hydrocarbons and polar compounds after dichloromethane extraction, and by gas chromatography-mass spectrometry (GC-MS) molecular analyses. The organic compounds observed were petroleum byproducts (steranes and terpanes, unresolved complex mixture (UCM) and polycyclic aromatic hydrocarbons (PAH)), but plant and bacteria biomarkers were also found (phytol and derivatives, sterols). Leachable OM consisted of 6% of sediment OM (associated with particles >0.45 microm). This leachable OM is easily extractable by dichloromethane (96%) and contains fewer macromolecules than other fractions. Isolated grain size fractions showed dissimilarities (total organic carbon from 3.5 mg/g to 88.6 mg/g, extraction rate from 24 to 96%, aromatic hydrocarbon distribution) and similarities (proportions of aromatic and saturated hydrocarbons and polar compounds, molecular distribution of saturated hydrocarbons and polar compounds). The results suggest that organic macromolecules take part in the aggregation of sediments and prevent fine particles (<10 microm) from being leached. On the other hand, leachable particles (20 microm grain size mode) could carry low molecular weight organic molecules. The physical structure of the sediments and the leaching of particles containing contaminants are considerably affected by the presence of OM.     

Disinfection by-products in filter backwash water: Implications to water quality in recycle designs

The overall purpose of this research was to investigate disinfection by-product (DBP) concentrations and formation potential in filter backwash water (FBWW) and evaluate at bench-scale the potential impact of untreated FBWW recycle on water quality in conventional drinking water treatment. Two chlorinated organic compound groups of DBPs currently regulated in North America were evaluated, specifically trihalomethanes (THMs) and haloacetic acids (HAAs). FBWW samples were collected from four conventional filtration water treatment plants (WTP) in Nova Scotia, Canada, in three separate sampling and plant audit campaigns. THM and HAA formation potential tests demonstrated that the particulate organic material contained within FBWW is available for reaction with chlorine to form DBPs. The results of the study found higher concentrations of TTHMs and HAA9s in FBWW samples from two of the plants that target a higher free chlorine residual in the wash water used to clean the filters (e.g., clearwell) compared to the other two plants that target a lower clear well free chlorine residual concentration. Bench-scale experiments showed that FBWW storage time and conditions can impact TTHM concentrations in these waste streams, suggesting that optimization opportunities exist to reduce TTHM concentrations in FBWW recycle streams prior to blending with raw water. However, mass balance calculations demonstrated that FBWW recycle practice by blending 10% untreated FBWW with raw water prior to coagulation did not impact DBP concentrations introduced to the rapid mix stage of a plant’s treatment train.     

A pilot-scale percolating filter for use in sewage treatment studies

A pilot-scale filter is described which can be quickly and easily constructed, even by those with limited engineering skills, using materials most of which are likely to be available in the stores department or on the site of a normal sewage works. It is robust, durable, easily modified and produces a well purified effluent using either mineral or random plastic media at conventional loadings. The simple design offers a low cost, reliable and versatile pilot-filter system suitable for a wide range of research, evaluation and development work.     

Chemical characterisation of natural organic substrates for biological mitigation of acid mine drainage

The current approach of the biological treatment of acid mine drainage by means of a passive remediation system involves the choice of an appropriate organic substrate as electron donor for sulphate reducers. Nowadays this selection is one of the critical steps in the performance of such treatment, as this depends to a great extent on the degradability of the organic substrate. Thus, a prior characterisation of the organic substrate predicting its biodegradability would be desirable before embarking on an extensive large-scale application. The aim of this study was to correlate the chemical composition (lignin content) of four different natural organic substrates (compost, sheep and poultry manures, oak leaf) and their capacity to sustain bacterial activity in an attempt to predict biodegradation from chemical characterisation. The results showed that the lower the content of lignin in the organic substrate, the higher its biodegradability and capacity for developing bacterial activity. Of the four organic materials, sheep and poultry manures and oak leaf evolved reducing conditions and sustained active sulphidogenesis, which coupled with the decrease in sulphate concentration indicated bacterial activity. Sheep manure was clearly the most successful organic material as electron donor (sulphate removal >99%), followed by poultry manure and oak leaf (sulphate removal of 80%). Compost appeared to be too poor in carbon to promote sulphate-reducing bacteria activity by itself. Column experiments emphasised the importance of considering the residence time as a key factor in the performance of continuous systems. With a residence time of 0.73 days, sheep manure did not promote sulphidogenesis. However, extending residence time to 2.4 and 9.0 days resulted in an increase in the sulphate removal to 18% and 27%, respectively.     

A semi-implicit finite element model for natural water bodies

In this work, a semi-implicit model, applied to the shallow water equations, is developed for natural water bodies. In the proposed model, the shallow water equations are integrated in the vertical direction, finite elements are employed in the spatial discretization, and finite differences in the time discretization. The model is based on the uncoupling of the governing equations, in which the expressions of the velocity components, obtained explicitly from the discretized momentum equations, are substituted in the continuity equation. Therefore, there is an uncoupling of the solution; initially the continuity equation is solved, and, in the sequence, the momentum equations are solved. Yet, this uncoupling produces a significant reduction in the number of equations of the resulting systems, when compared to standard coupled systems. This reduction improves substantially the computer performance.     

Hydraulic linkage of a storm water tank to a karst spring (Gallusquelle)

Grundwasser - A&nbsp;significant proportion of the global water supply is ensured by karst aquifers. However, these are often highly vulnerable to contamination. A&nbsp;storm water tank...     

Membrane filter procedure for enumeration of Pseudomonas aeruginosa in water

In this report, the efficiency of replacing the antibiotics in mPA-C and mPA-D agars by C-390 as selective agent, has been studied, and compared with MPN procedure. In a second step a resuscitation technique to recover stressed Pseudomonas aeruginosa cells has been tested with the mentioned MF media. Counts obtained with MPN technique were always significantly higher than when using MF without resuscitation. No significant differences were obtained between MPN and MF technique when the resuscitation step was used with the second one. mPA-C390 and mPA-D390 present the advantage of being autoclavable and specific for selective isolation of P. aeruginosa from different kinds of waters.     

Development of maize cob‐based biochar filter for water purification

The study aimed at biochar production from maize cob and its performance in improving water physiochemical attributes. Three feedstock masses (2, 2.5, 3 kg) were used for biochar production. Nine treatment combinations of T1L1, T1L2, T1L3, T2L1, T2L2, T2L3, T3L1, T3L2 and T3L3 in triplicate were used for biochar performance. Biochar yield of 50% was averagely achieved at slow pyrolysis conditions (300 to 600°C) and 120 min residence time. Biochar had 4.13% moisture content, 6.86% ash, 17.70% volatile matter, 71.28% fixed carbon, and a pH of 10.27. Odour, colour, and total hardness of the wastewater improved after filtration using biochar to acceptable levels for potable water use. Total hardness reduced by 51.9% in T2L2 and 44.4% in T3L2. Findings front maize cob biochar as a purification technology for domestic potable water use. There is need for maize cob biochar performance on heavy metals and when it is sandwiched with other materials.     

Epidemiological studies related to enhanced natural radiation: Possibilities and problems

Ultimately epidemiological studies alone provide the means to determine whether or not persons exposed to specified levels of enhanced natural radiation are at increased risk of developing cancers or other diseases. Various types of epidemiological study can be used to examine this issue, but each type has problems and limitations. In order to be viable any study must satisfy certain basic criteria concerning sample size, timespan, data quality, and allowance for confounding factors.     

Long-term storage of natural water samples for dissolved oxygen determination

A method for preserving natural water samples for dissolved oxygen analysis is recommended. The conventional method of using greased glass stoppers have been found to cause an increase in oxygen concentration by 12% over 1-month period as a result of evaporation of water sample through micro-gaps and concurrent intrusion of air into the water sample bottles. Sealing the sample bottles with water has been found to be the optimal storage method. It permits a 100.2 +/- 0.3% recovery of dissolved oxygen concentration from storage seawater samples over 4 months.     

Comparison of batch sorption tests, pilot studies, and modeling for estimating GAC bed life

Saint Paul Regional Water Services (SPRWS) in Saint Paul, MN experiences annual taste and odor episodes during the warm summer months. These episodes are attributed primarily to geosmin that is produced by cyanobacteria growing in the chain of lakes used to convey and store the source water pumped from the Mississippi River. Batch experiments, pilot-scale experiments, and model simulations were performed to determine the geosmin removal performance and bed life of a granular activated carbon (GAC) filter-sorber. Using batch adsorption isotherm parameters, the estimated bed life for the GAC filter-sorber ranged from 920 to 1241 days when challenged with a constant concentration of 100 ng/L of geosmin. The estimated bed life obtained using the AdDesignS model and the actual pilot-plant loading history was 594 days. Based on the pilot-scale GAC column data, the actual bed life (>714 days) was much longer than the simulated values because bed life was extended by biological degradation of geosmin. The continuous feeding of high concentrations of geosmin (100-400 ng/L) in the pilot-scale experiments enriched for a robust geosmin-degrading culture that was sustained when the geosmin feed was turned off for 40 days. It is unclear, however, whether a geosmin-degrading culture can be established in a full-scale filter that experiences taste and odor episodes for only 1 or 2 months per year. The results of this research indicate that care must be exercised in the design and interpretation of pilot-scale experiments and model simulations for predicting taste and odor removal in full-scale GAC filter-sorbers. Adsorption and the potential for biological degradation must be considered to estimate GAC bed life for the conditions of intermittent geosmin loading typically experienced by full-scale systems.     

生物沸石滤池去除微污染水源水中氨氮的挂膜启动

对沸石滤料生物滤池处理微污染水源水中低浓度氨氮的挂膜启动性能进行了研究。试验结果表明,挂膜过程可以根据氨氮、亚硝酸盐氮、硝酸盐氮浓度的变化分为三个阶段：初期沸石发挥本身对铵离子的吸附交换性能,氨氮去除率达88％以上;中期开始出现生物硝化作用,亚硝酸盐积累明显,硝酸盐出水浓度不稳定,氨氮去除率稳定,但下降至65％左右;后期硝化反应稳定进行,亚硝酸盐迅速转化为硝酸盐,氨氮去除率稳定在60％以上。生物沸石滤池挂膜同时应考察亚硝酸盐氮、硝酸盐氮浓度变化,在出水亚硝酸氮明显积累后又稳定降低,且硝酸盐氮稳定积累时方可认为挂膜成功。进出水pH值的变化可以指示硝化反应的进行程度和生物膜形成阶段。     

Cucurbituril for water treatment. Part I: Solubility of cucurbituril and sorption of reactive dyes

Cucurbituril was investigated regarding its potential as a sorbent for the removal of reactive dyes from model solutions and authentic wastewaters. The solubility of cucurbituril is low in pure water but increases in the presence of salts. When dyes sorbing onto cucurbituril are present, solubility is drastically decreased compared to dye-free media. Sorption efficiency depends on salt concentration and salt species. Moderate salt concentrations favor sorption, high concentrations lead to cucurbituril dissolution. Divalent ions have a stronger effect than monovalent ions and larger ions more than smaller ones. In tests with authentic wastewaters cucurbituril was partially (20-100%) dissolved and contaminant removal was inefficient. Because of its solubility, cucurbituril is not feasible as a sorbent in wastewater treatment unless it could be covalently fixed onto a suitable support material.     

Use of some natural and waste materials for waste water treatment

A fundamental study was conducted to assess removal and filtration capacity of waste and natural indigenous materials as treatment mediums e.g., shell, limestone, waste paper mixed with refuse concrete, refuse cement, also processed nitrolite, charcoal-bio and charcoal. Under room temperature condition removal of phosphoric, nitric and ammonium-ions, filtration of suspended substance (SS) together with removal of COD in waste water was investigated. Influence of particle size effect for all treatment mediums except for waste paper was pursued. Significant improvement of waste water quality with respect to SS, phosphoric ions and decrease in COD is possible by treating with these filtration mediums. With specific reference to some treatment mediums NO3-N and NH4-N showed reasonable improvement in quality, although generally removal effect was not very significant. Efficacy of treatment was dependent on the particle size of treatment mediums in general, however, nitrolite for NH4--N, charcoal-A for SS and COD, refuse cement mixed with waste paper for PO4 ion removal showed insignificant variability on the particle size effect. Results of this fundamental study demonstrate effectiveness and feasibility for applied application of these proposed waste and naturally available treatment ingredients at lower cost.     

Structure of nitrifying biofilms in a high-rate trickling filter designed for potable water pre-treatment

This study examined the composition and structure of nitrifying biofilms sampled from a high-rate nitrifying trickling filter which was designed to pre-treat raw surface water for potable supply. The filter was operated under a range of feed water ammonia and organic carbon concentrations that mimicked the raw water quality of poorly protected catchments. The biofilm structure was examined using a combination of fluorescence in situ hybridisation and scanning electron microscopy. Biopolymers (carbohydrate and protein) were also measured. When the filter was operated under low organic loads, nitrifiers were abundant, representing the majority of microorganisms present. Uniquely, the study identified not only Nitrospira but also the less common Nitrobacter. Small increases in organic carbon promoted the rapid growth of filamentous heterotrophs, as well as the production of large amounts of polysaccharide. Stratification of nitrifiers and heterotrophs, and high polysaccharide were observed at all filter bed depths, which coincided with the impediment of nitrification throughout most of the filter bed. Observations presented here specifically linked biofilm structure with filter functionality, physically validating previous empirical modelling hypotheses regarding competitive interactions between autotrophic and heterotrophic bacteria in biofilms.     

A membrane filter technique for the concentration and detection of Salmonella from drinking water

A methodology for the concentration, detection and enumeration of Salmonella from drinking water by membrane filter technique is described. A single step filtration methodology for enteroviruses and Salmonella was not possible, due to the inactivation of Salmonella at conditions necessary for concentration of enteroviruses, i.e. pH 3.5 and 9.5. Enrichment in selenite cystine broth and incubation at 37°C followed by plating on brilliant green agar provided maximum recovery of Salmonella. Out of 21 drinking water samples in Delhi, India examined during March to May 1991, three were positive for Salmonella.     

Experimental studies on natural smoke filling in atrium due to a shop fire

How smoke spilling out of a shop fire would fill up an atrium has been studied experimentally in this paper. Full-scale burning tests were carried out in the PolyU/USTC Atrium constructed in Hefei, China. Since balcony spill plume expressions appeared in the literature might not be applicable for a shop fire with finite width, two plume models for smoke spilling out of a shop fire inside an atrium were proposed and assessed. An equation on studying the smoke layer interface height with a two-layer approach was derived.