Performance of infiltration swales with regard to operation in winter times in an Alpine region

In cold climate regions winter conditions significantly influence the performance of stormwater infiltration devices. Frozen soil and water storage by snow changes their operation. In this paper winter operation of a grassed infiltration swale was investigated using on-site and laboratory measurements. The field investigation of a grassed swale at a parking place in an Alpine region showed that the swale fulfilled its function properly. Although the top layer was frozen for some time, the storage capacity of the swale was sufficient to store the precipitation until the conditions improved. The soil attenuated the air temperature, at 20 cm below ground surface the soil was only frozen for one week. winter maintenance proved to be a problem, together with the snow from the parking place a lot of gravel and fine particles were deposited at one end of the swale. This decreased the hydraulic conductivity at that point significantly. The laboratory tests with soil columns showed an increase of flow time through the soil column with decreasing soil moisture content. For soil temperatures below 0 degrees C the hydraulic conductivity was reduced for increasing initial soil moisture contents. All in all the hydraulic conductivity was best around 0 degrees C for all soil water contents. However, also at minus 5 degrees C the coefficient of hydraulic conductivity was always at least above 10(-6) m/s, thus within the range of tolerated hydraulic conductivity specified in the national guidelines. Nevertheless, the handling of the soil was found to have high influence on the results. The results indicate that in the Alpine region infiltration swales operate sufficiently under winter conditions although with decreased performance.     

Combined biological and physico-chemical treatment of baker's yeast wastewater.

The UASB reactor (35 degrees C) was quite efficient for removal of bulk COD (52-74%) from the raw and diluted cultivation medium from the first separation process of baker's yeasts (the average organic loading rates varied in the range 3.7-16 g COD/I/d). The aerobic-anoxic biofilter (19-23 degrees C) can be used for removal of remaining BOD and ammonia from anaerobic effluents; however, it had insufficient COD to fulfil the denitrification requirements. To balance COD/N ratio, some bypass of raw wastewater (approximately 10%) should be added to the biofilter feed. The application of iron (III)-, aluminium- or calcium-induced coagulation for post-treatment of aerobic effluents can fulfil the limits for discharge to sewerage (even for colour mainly exerted by hardly biodegradable melanoidins), however, the required amounts of coagulants were relatively high.     

Combined biological and physico-chemical treatment of baker's yeast wastewater including removal of coloured and recalcitrant to biodegradation pollutants.

The UASB reactor (35 degrees C) was quite efficient for removal of bulk COD (62-67%) even for such high strength and recalcitrant wastewater as the cultivation medium from the first separation process of baker'syeasts (the average organic loading rates varied from 3.7 to 10.3 g COD/l/d). The aerobic-anoxic biofilter (20 degrees C) can be used for removal of remaining BOD and ammonia from strong nitrogenous anaerobic effluents; however, it suffered from COD-deficiency to fulfil denitrification requirements. To balance the COD/N ratio, some bypass of raw wastewater should be added to the biofilter feed. The application of iron chloride coagulation for post-treatment of aerobic effluents may fulfil the discharge limits (even for colour mainly exerted by hardly biodegradable melanoidins) under iron concentrations around 200 mg/l.     

Integrated biological (anaerobic-aerobic) and physico-chemical treatment of baker's yeast wastewater.

The UASB reactor (35 degrees C) was quite efficient for removal of bulk COD (52-74%) from simulated (on the basis of cultivation medium from the first separation process) general effluent of baker's yeast production (the average organic loading rates varied from 8.1 to 16 g COD/l/d). The aerobic-anoxic biofilter (19-23 degrees C) can be used for removal of remaining BOD and ammonia from anaerobic effluents; however, it suffered from COD-deficiency to fulfil denitrification requirements. To balance COD/N ratio, some bypass (approximately 10%) of anaerobically untreated general effluent should be added to the biofilter feed. The application of iron (III)-, aluminium- or calcium-induced coagulation for post-treatment of aerobic-anoxic effluents can fulfil the limits for discharge to sewerage (even for colour mainly exerted by hardly biodegradable melanoidins), however, the required amounts of coagulants were relatively high.     

Effects of phosphorus limitation and temperature on PHA production in activated sludge.

The study was designed to investigate the effects of temperature and phosphorus limitation on polyhydroxyalkanoate (PHA) production and storage by activated sludge biomass. The two-stage operation approach, i.e. a growth phase followed by a nutrient limitation phase, was applied to induce PHA accumulation. The pre-selected temperatures of 10, 20 and 30 degrees C were investigated under phosphorus limitation conditions using three four-litre fully aerobic SBR systems operated at an SRT of 10 days with cycle time and HRT of 6 and 10 hours. PHA production was greater in the 10 degrees C system than in the 20 degrees C and 30 degrees C systems but there was little difference between the two higher temperatures. The maximum PHA fractions of the sludge were 52, 45 and 47%TSS for the three temperatures from low to high, and the maximum PHA concentrations in the mixed liquors were 1,491, 1,294 and 1,260 mg/l, respectively. However, it was observed that very low values of PHA yield per unit COD consumed were obtained, i.e., 0.05, 0.03 and 0.04 mgPHA/mgCODu, for the 10, 20 and 30 degrees C reactors, respectively. This was because all three systems required several days to reach maximum PHA accumulation in their mixed liquor biomasses. It is probable the bacteria still had some stored poly-P in their cells upon initiation of the phosphorus limited influent, and PHA accumulation was delayed until the stored phosphorus was depleted. Also, PHA productivity was reduced by the large amounts of biomass lost from the systems because of sludge bulking.     

Biodegradation of phenol at low temperature using two-phase partitioning bioreactors.

Two-phase partitioning bioreactors offer many advantages for the removal of toxic pollutants. In particular, such systems can be loaded with very large quantities of pollutants without risks of microbial inhibition, they are self-regulated and they prevent the risks of hazardous pollutant volatilisation during aerobic treatment. However, their potential has never been tested at low temperatures. Phenol biodegradation by a cold adapted Pseudomonas strain was therefore tested at 14 or 4 degrees C using 2-undecanone, diethyl sebacate or 2-decanone as organic phases in a two-phase partitioning bioreactor. The three solvents were biocompatible at 14 degrees C but evidence was found that diethyl sebacate was biodegraded by the bacteria and this solvent was not tested further. Although only 2-decanone was suitable at 4 degrees C, phenol biodegradation was more efficient in 2-undecanone at 14 degrees C, reaching a maximum volumetric rate (based on the volume of aqueous phase) of approximately 1.94 g/L.day after 47 h of cultivation. In 2-decanone at 14 degrees C, evidence was found that phenol degradation was limited by the release of biosurfactants, which increased the solubility and toxicity of the solvent in the aqueous phase inhibiting microbial activity. This study therefore shows that pollutant removal at low temperature is feasible but that the production of biosurfactants can have a negative impact on the process and must be taken into consideration when selecting the organic solvent. Future work should therefore focus on the selection of solvents suitable for use at temperatures below 14 degrees C.     

Biofiltration of H(2)S with reclaimed water as a nutrient/moisture source at loading rates from 10 to 300 g H(2)S m(-3) h(-1)

A biofilter was evaluated with two different media under field conditions using reclaimed water as a nutrient source. Evaluation with a single medium demonstrated that H(2)S could be efficiently removed at volumetric loading rates of up to 200 g H(2)S m(-3) h(-1). After an extended period of high loading rates, the performance began to deteriorate at loading rates greater than 150 g H(2)S m(-3) h(-1) possibly due to nutrient limitations. The reclaimed water served as a nutrient source even though the primary form of nitrogen was nitrate. The reclaimed water successfully supplied nutrients at the majority of loading rates observed in the study and this was verified by stoichiometric calculations. The biofilter was converted to a dual media filter and consistent performance was also observed with the dual media filter at loading rates up to 150 g H(2)S m(-3) h(-1). The biofilter was successfully operated at loading rates higher than previously reported under field conditions. The use of nitrate in reclaimed water as a nitrogen source was successful and demonstrated the potential to eliminate the need for a separate nutrient source at a water reclamation plant.     

Biofiltration as pre-treatment to water harvesting and recycling

This paper presents the results of the long term biofilter experiments conducted with raw stormwater collected from a canal at Carlton, in Sydney. Anthracite and granular activated carbon (GAC) were used as a single filter media in biofilter columns. Media heights of 75 and 40 cm were used. The filter columns were operated at filtration velocities of 0.12 and 0.25 m/h. The removal efficiency for turbidity and DOC for the GAC filter media were found to be 75% and almost 100% respectively. The removal efficiency for the anthracite filter was much lower. Molecular weight distribution analysis showed an almost similar trend to the DOC removal. Compared with anthracite filter media, the GAC biofilter removed a much larger range of organic compounds present in the stormwater. The GAC biofilter removes organic matter earlier as compared to anthracite. Based on a limited sample of stormwater, the removal efficiency for phosphorus was upto 74% and that of nitrogen was up to 30%. In general GAC filter shows higher heavy metal removal efficiency than anthracite. The removal of zinc, iron, lead and nickel were good. However the concentration of heavy metal in the raw surface water sample was low.     

Algal growth response and survival in a range of light and temperature conditions: implications for non-steady-state conditions in waste stabilisation ponds.

Growth and physiological experiments were carried out using Scenedesmus subspicatus and Chlorella vulgaris as representative species typically found in waste stabilisation ponds. These experiments were designed to test the ability of the organisms to survive and grow under a range of different temperatures and light intensities that might occur in mid to high latitude regions. Growth was assessed using optical density and photosynthetic rate for a combination of temperatures of 5, 10, 15 and 20 degrees C at light intensities of 7.8, 15.7, 31.3, 47, 62.7 and 78.3 micromolm(-2) sec(-1). C. vulgaris had a higher rate of growth and photosynthetic activity than S. subspicatus at low temperatures but had reached its maximum growth rate at 15 degrees C. S. subspicatus showed a higher growth rate than C. vulgaris at higher temperatures, and did not achieve its maximum growth rate over the range of temperatures studied. For both species light was not limiting to growth above 47 micromol m(-2) sec(-1). Survival of the two species under dark conditions was tested at 4 degrees C and - 20 degrees C using direct plating and growth tests. C. vulgaris was able to survive at 4 degrees C for a much longer period than S. subspicatus and a portion of the population was able survive - 20 degrees C. The different responses of the two species to dark and cold conditions are indicative of the range that may occur across a wider population, and show why in practice some species may appear earlier and compete more effectively in early spring but then lose advantage as the temperature and light intensity increases into the summer.     

Dynamical modelling of an activated sludge system of a petrochemical plant operating at high temperatures.

The Mexican petrochemical industry, Morelos S.A. de C.V., is one of the biggest and more important petroleum industries in Mexico and Latin America. It has an activated sludge system to treat its wastewater flow, which is approximately 7,000 m3/d. The wastewater contains volatile organic carbon substances classified as toxics. The old surface aeration system was changed for fine bubble diffusers; however, one major drawback of the new aeration system is that the temperature in the bioreactor has increased due to the compression of the air, which at the compressor exit reaches 85 degrees C. This effect results in the temperature in the bioreactor attaining 32 degrees C during the fall, whereas in the spring and summer, the bioreactor temperature reaches higher values than 40 degrees C. The high temperatures reduce the microorganism activity and cause a higher volatilisation rate of volatile compounds, among other effects, which affect the performance of the biological treatment. This work was performed to obtain a better modelling of the wastewater treatment from the petrochemical industry. The model describes the effect of the temperature on the performance of the biological treatment. The model was obtained from tests that were carried out in laboratory reactors with 14 L capacity, which were operated at different temperatures (from 30 to 45 degrees C), with the same wastewater and conditions as the actual system.     

Two-stage thermophilic-mesophilic anaerobic digestion of waste activated sludge from a biological nutrient removal plant.

A two-stage thermophilic-mesophilic anaerobic digestion pilot-plant was operated solely on waste activated sludge (WAS) from a biological nutrient removal (BNR) plant. The first-stage thermophilic reactor (HRT 2 days) was operated at 47, 54 and 60 degrees C. The second-stage mesophilic digester (HRT 15 days) was held at a constant temperature of 36-37 degrees C. For comparison with a single-stage mesophilic process, the mesophilic digester was also operated separately with an HRT of 17 days and temperature of 36-37 degrees C. The results showed a truly thermophilic stage (60 degrees C) was essential to achieve good WAS degradation. The lower thermophilic temperatures examined did not offer advantages over single-stage mesophilic treatment in terms of COD and VS removal. At a thermophilic temperature of 60 degrees C, the plant achieved 35% VS reduction, representing a 46% increase compared to the single-stage mesophilic digester. This is a significant level of degradation which could make such a process viable in situations where there is no primary sludge generated. The fate of the biologically stored phosphorus in this BNR sludge was also investigated. Over 80% of the incoming phosphorus remained bound up with the solids and was not released into solution during the WAS digestion. Therefore only a small fraction of phosphorus would be recycled to the main treatment plant with the dewatering stream.     

Effects of filtration temperature, humic acid level and alum dose on cryptosporidium sized particle breakthrough.

Recent Cryptosporidium outbreaks have highlighted concerns about filter efficiency and especially particle breakthrough. Understanding the causes of breakthrough is essential, as the parasite cannot be destroyed by conventional disinfection with chlorine. Particle breakthrough depends on many factors. This research aims to investigate the influence of temperature, humic acid (HA) level and chemical dosing on particle breakthrough in filtration. A series of temperatures were set at 5 degrees C, 15 degrees C and 25 degrees C; humic acid level was 5 mg L(-1). Each was combined with a series of Al doses. A laser particle counter was used to assess the particle breakthrough online. Turbidity, zeta potential, and UV254 absorption were measured before and after filtration. The results showed that particle breakthrough was influenced significantly by temperature, humic acid and dosing. Particle breakthrough occurred earlier at lower temperature, while at higher temperature it was reduced at the same coagulant dose. With coagulants, even at low dose, particle breakthrough was significantly reduced. With HA 5 mg L(-1), particle breakthrough was earlier and the amount was much larger than without HA even at high temperature. There was an optimal dose in filtration and it was well correlated with zeta potential.     

Low-temperature post-treatment of anaerobically treated-sewage in anaerobic filter with cationic-polymer addition.

The post-treatment of domestic sewage pretreated in a 6 m3 UASB was investigated in two high-rate anaerobic filter (AF) reactors operated in parallel. The difference between the two AF reactors was only the addition of cationic polymer to the second reactor (AF + P). The reactors were operated at low temperatures, ranged between 13 and 20 degrees C. The media in each AF reactor consisted of vertical sheets of reticulated-polyurethane foam (RPF) with knobs. The results demonstrated that the AF + P reactor (HRT = 3 h) with cationic polymer addition (2 mg/L) was an efficient system for post-treatment. The removal efficiencies for total, suspended, colloidal and dissolved COD were, respectively, 41, 86 and 76 and 12% in the AF + P reactor and they were, respectively, 80, 97, 77 and 66% in the UASB + (AF + P) system. The removal of total, suspended and colloidal COD in the UASB + (AF + P) system were significantly higher than those achieved in the UASB + AF system. As hardly any nutrient was removed in the UASB + (AF + P) system, the effluent after pathogen removal is a valuable product for irrigation and fertilisation to close the water and nutrients cycle.     

Identifying Temperature Thresholds Associated with Fish Community Changes in British Columbia,Canada, to Support Identification of Temperature Sensitive Streams

We collected fish samples and measured physical habitat characteristics, including summer stream temperatures, at 156 sites in 50 tributary streams in two sampling areas (Upper Fraser and Thompson Rivers) in British Columbia, Canada. Additional watershed characteristics were derived from GIS coverages of watershed, hydrological and climatic variables. Maximum weekly average temperature (MWAT), computed as an index of summer thermal regime, ranged from 10 to 23 °C. High values of MWAT were associated with large, warm, low relief watersheds with a high lake influence. Measures of community similarity suggested that the fish community changed most rapidly through a lower transition zone at an MWAT of about 12 °C and an upper transition zone at an MWAT of about 19 °C. These results were confirmed using existing fisheries inventory data combined with predictions of MWAT from a landscape‐scale regression model for the Thompson River watershed. For headwater sites in the Chilcotin River watershed (which drains into the middle Fraser River), the relative dominance of bull trout versus rainbow trout (based on inventory data) decreased with increasing predicted MWAT although the distinction was not as clear as for the Thompson River sites. The fish communities in these watersheds can be characterized in terms of very cold water (bull trout and some cold water species), cold water (salmonids and sculpins) and cool water (minnows and some cold water salmonids). The two transition zones (ca 12 and 19 °C) can be used to identify thresholds where small changes in stream temperature can be expected to lead to large changes in fish communities. Such clear, quantifiable thresholds are critical components of a management strategy designed to identify and protect vulnerable fish communities in streams where poor land use practices, alone or in combination with climatic change, can lead to changes in stream temperatures. Copyright © 2015 John Wiley & Sons, Ltd.     

Mitigation of cold‐water thermal pollution downstream of a large dam with the use of a novel thermal curtain

Hypolimnial releases from dams during periods of thermal stratification modify the downstream riverine thermal regime by decreasing water temperature and reducing natural diel thermal variability. This cold‐water thermal pollution in rivers can persist for hundreds of kilometres downstream of dams and impact important ecological processes such as fish spawning. To mitigate this problem, a first‐of‐its‐kind thermal curtain was fitted to the large bottom release Burrendong Dam on the Macquarie River, Australia. The thermal curtain acts by directing warmer, near‐surface epilimnial water to the low‐level hypolimnial offtake. This study aimed to test the efficacy of the thermal curtain by measuring temperatures before and after the curtains installation, quantifying the magnitude and extent of cold‐water thermal pollution along the Macquarie River downstream of Burrendong Dam. Epilimnial releases with use of the curtain increased diel temperature ranges and the mean monthly water temperature below the dam. Epilimnial releases with use of the curtain increased diel temperature ranges from 0.9°C to 2.5°C and reduced the difference between the mean monthly water temperature of an upstream control and a downstream site by up to 3.5°C. A comparison of the monthly temperature means along the river, indicated that thermal recovery, whereby temperatures returned to within the natural range of upstream temperatures occurred 45 km downstream of the dam during summer when the thermal curtain was deployed, compared with approximately 200 km prior to deployment of the curtain. Our study suggests that the use of thermal curtains can reduce cold‐water thermal pollution and improve ecological outcomes for river ecosystems downstream of dams.     

Preservation of nutrients during long-term storage of source-separated yellowwater

Source separation of human urine (yellowwater) enhances the sustainability of wastewater management and efficiency of nutrient recovery and recycling. Storage of source-separated yellowwater is recommended prior to agronomic reuse. At this point, it is of immense interest to determine the effect of storage time on quality of yellowwater. Therefore, this study focused on examining changes in some chemical properties of raw, undiluted, freshly collected, source-separated yellowwater stored for a period of 1 year under different temperature regimes: cold (4 °C), mild (10 °C) and warm (22 °C). Chemical parameters (biochemical oxygen demand (BOD(5)), N-tot, N-NO(2), N-NO(3), N-NH(4), P-tot, K, S, and pH), with the main focus on fertiliser nutrient compounds intended for agricultural utilisation, were tested. The outcomes revealed that both nitrification and denitrification processes took place in the stored yellowwater, and an increase in the pH level of up to pH greater than 9 was observed. The study found that the main macronutrients can be well preserved in yellowwater, as there were no substantial changes in the contents of these elements over a 1 year storage period at the three temperatures tested.     

Modelling hydrogen sulphide emission in a WWTP with UASB reactor followed by aerobic biofilters.

Hydrogen sulphide (H2S) represents one of the main odorant gases emitted from wastewater treatment plants (WWTP) and a mathematical model can be a fast and low cost tool to estimate its emission. In this work H2S emission rates in a WWTP, composed of an up-flow anaerobic sludge blanket (UASB) reactor and an aerobic biofilter (BF), are estimated using four mathematical models available in the literature (AP-42, GPC, TOXCHEM + and WATER8). The results show that the GPC model leads to the best agreement with the experimental data, except for the biofilter due to its lack of capability to include biodegradation as a H2S removal process. On the other hand, the AP-42 and WATER8 models showed a slightly better ability to predict H2S removal in the biofilter than the TOXCHEM + model, as all models underestimate the H2S concentration decay.     

Zero-valent iron treatment of RDX-containing and perchlorate-containing wastewaters from an ammunition-manufacturing plant at elevated temperatures.

The use of zero-valent iron for treating wastewaters containing RDX and perchlorate from an army ammunition plant (AAP) in the USA at elevated temperatures and moderately elevated temperature with chemical addition was evaluated through batch and column experiments. RDX in the wastewater was completely removed in an iron column after 6.4 minutes. Increasing the temperature to 75 degrees C decreased the required retention time to 2.1 minutes for complete RDX removal. Perchlorate in the wastewater was completely removed by iron at an elevated temperature of 150 degrees C in batch reactors in 6 hours without pH control. Significant reduction of perchlorate by zero-valent iron was also achieved at a more moderate temperature (75 degrees C) through use of a 0.2 M acetate buffer. Based on the evaluation results, we propose two innovative processes for treating RDX-containing and perchlorate-containing wastewaters: a temperature and pressure-controlled batch iron reactor and subsequent oxidation by existing industrial wastewater treatment plant; and reduction by consecutive iron columns with heating and acid addition capabilities and subsequent oxidation.     

Quantifying the influence of cold water intrusions in a shallow,coastal system across contrasting years: Green Bay,Lake Michigan

We present water column thermal structure for two climatically different years: 2012, which experienced abnormally warm spring and summer air temperatures preceded by a relatively low ice winter and 2013, which experienced cooler than average spring and average summer air temperatures and preceded by average ice conditions. Mean bottom water temperatures for the season and during cold water intrusions were significantly warmer in 2012 than 2013 leading to a significantly reduced stratified season in 2012. Cold water intrusions were driven into southern Green Bay by southerly winds while intrusions were terminated when winds switched to persistent northerly winds. 2012 observed a significant increase in northerly winds relative to 2013, decreasing cold water intrusion presence and duration but winds did not fully explain the difference in thermal conditions for southern Green Bay. These cold bottom waters drive stratification in polymictic southern Green Bay while dimictic waters were found to have significantly warmer bottom temperatures during 2012 and a deeper mixed layer. Our observations suggest that relatively shallow (<20?m), seasonally stratified systems may not increase in stratification strength and duration under a warming climate; rather, changing wind climatology and surface heat flux can inform the degree to which the mixing regime can be expected to change and impact stratification and thermal structure of coastal systems. We discuss the biogeochemical implications of different thermal regimes, particularly within the context of multiple drivers of physical water column structure in eutrophic, stratified coastal systems.     

Influence of dietary nutrients on low temperature tolerance of freshwater alewives

Although mass mortality of alewives (Alosa pseudoharengus) exposed to cold temperatures can be a destabilizing force in the interactions between salmonines and alewives in the Great Lakes, the physiological basis of these events is poorly understood. To examine the influence of diet on acute exposure to cold temperatures, we fed alewives two commercial frozen foods (Artemia and Daphnia) which differed in nutritional composition. Compared to Daphnia, the Artemia contained higher levels of key nutrients (polyunsaturated fatty acids, carnitine, and vitamin E) that have been implicated in cold tolerance of fishes. When exposed to a laboratory cold challenge, the alewives maintained on frozen Artemia exhibited significantly lower mortality rates than those fed frozen Daphnia. Of the three nutrients examined, vitamin E may be most responsible for enhancing cold tolerance since levels of this nutrient were significantly elevated in the Artemia-fed fish. More information regarding the nutritional composition of alewife diets would improve our understanding of alewife cold-temperature mortality and may eventually lead to better management of salmon and trout populations in the Great Lakes.