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The interactions between aqueous humic substances (HS), the principal component of natural organic matter, and phosphorus (P), an important nutrient, are complex and poorly understood. Past research has shown that P has the potential to form complexes with HS in fresh waters. Humic complexation may change P bioavailability within such waters and, in addition, influence the transport of phosphorus within catchment settings. This project aims at examining the relationships and associations of P, HS, and iron (Fe) in Loch Meadie, Sutherland, northern Scotland, which has been assessed as reference condition with respect to P. "Reference condition" means the loch should not have been disturbed or only minimally impacted by human activities. Results will be used for identifying characteristic parameters which can enhance the performance of the model used to predict reference condition total phosphorus (TP) concentrations for highly-coloured Scottish lochs under the Water Framework Directive. Apart from Loch Meadie, samples collected from other reference condition lochs in northern Scotland and Shetland were also analysed in order to enhance our understanding of the relationship between TP and HS by including different colour types of reference condition lochs (clear water, mesohumic and polyhumic water). Significant seasonal trends in the water colour and total Fe (TFe) were observed from the Loch Meadie (Swordly) monthly samples. From mid-autumn to early winter (October-December), the water colour and TFe was typically higher than in the other seasons. The HS in Loch Meadie (Swordly) had relatively small molecular weight and low aromaticity, which was closer to fulvic acid rather than humic acid. According to the results of the 16 northern Scotland (mainland) and Shetland lochs, the total organic carbon (TOC) / dissolved organic carbon (DOC) and water colour were higher in polyhumic lochs than mesohumic lochs. The TP and total filterable P (TFP) varied in water samples collected from different lochs, whereas the TFe and total filterable Fe (TFFe) in polyhumic lochs was generally higher than that in mesohumic lochs. Ultrafiltration was used to isolate the colloidal component from loch waters, which was then fractionated by gel filtration chromatographic and centrifugal ultrafiltration methods. The gel filtration chromatographic fractionation of the colloids revealed two brown-coloured bands which had distinctive UV/Vis spectral features. The first eluting band had larger and more aromatic HS molecules than the second band, and in addition both P and Fe were primarily associated with the larger, more aromatic HS. This result demonstrated that P was able to form complexes with HS, in particular larger and more aromatic humic molecules, under the presence of Fe in the dissolved fraction of loch waters. Results from the centrifugal ultrafiltration method agreed with the gel filtration chromatographic results. The SEM-EDX results showed that P was likely bound with both the organic and inorganic particles in the particulate fraction of loch waters, however, the detailed binding mechanism between P and suspended solids was unclear and needs further investigation. Based on the main findings of this research, the current WFD models were improved by adding two new parameters, UV254nm (or SUVA254nm) and Total Suspended Solids. The new TP models, compared to the WFD non-humic model which is currently used by SEPA, gave significantly better prediction of the reference TP concentrations in most of the highly coloured Scottish lochs studied in this research.

The tightening of wastewater discharge standards for environmental protection and the increasing requirements for wastewater reuse have pushed for further tertiary treatment of wastewater to remove pollutants including suspended solids. This thesis explores the process science behind the removal of suspended solids from wastewater secondary effluent with the aim of improving the process for high quality effluent and efficient operation. Treatment plants receive diurnal flows and wastewater quality which challenges the production of a consistent compliant quality which meets reuse or discharge standards to receiving water bodies. A pilot-scale quadruple media filter was operated at the Cranfield Sewage Works to investigate the removal of suspended solids from secondary treated wastewater effluent under controlled and variable hydraulic loading rate, solids concentration and different wastewater characteristics. To measure the solids removal and operational performance of the filter, total suspended solids, turbidity, particle size analysis, zeta potential, headloss and temperature were measured under different operational conditions such as wastewater hydraulic loading rate, pH, solids concentration and filter depth. The media materials were examined to determine how they could be used to improve process performance and yield improved predictions in the application of filter models. A new method was developed for measuring the sphericity of media grains which improves the application of filter theory models to irregular shaped media grains. The method measured accurately the sphericity of glass spheres as 1.01 ± 0.02; the determined sphericity values correlated well with the measured headloss through filter media beds. The organic matter in the wastewater masked the media surface charge characteristics through coating on the media surface. Aggregation and deposition of wastewater solids was found to be most efficient near neutral pH. Adjustment of operational conditions were also explored. The solids removal efficiency of the filter varied inversely with an increase in hydraulic loading rate. However, multiple media layers reduced the negative impact of increased hydraulic loading rate and moderated headloss development. Particle retention was predominantly in the first 0.1 m depth of the filter, with further increases in filter depth producing marginal performance improvements whilst the headloss developed more quickly, reducing filter run times and wastewater throughput. While the specific deposit increased with rising influent concentration, the solids removal efficiency reduced. Thus, for an increase in the influent solids concentration of 10 mgL-1, the specific deposit increased by a factor of 1.2 while the removal efficiency decreased by an average factor of 0.9. Thus, the effluent deteriorates with increase in influent concentration while the filter holds more solids.

In 1995, the Environment Agency for England and Wales developed urban runoff treatment wetlands at two selected locations in Outer London. The systems have been monitored for a wide range of parameters including heavy metals, suspended solids and BOD over a period of two years. Seven storm events were also monitored. The ability of micro-organisms, isolated from the rhizosphere of wetland plants collected at both systems, to tolerate and accumulate heavy metals has also been investigated. This study has demonstrated that constructed wetland treatment systems are capable of reducing the pollutant loadings associated with urban runoff, and that such systems can be successfully established within urban areas. During dry weather, pollutant concentrations and loadings were typically low and associated removal efficiencies highly variable. However, during storm events, pollutant loadings increased and removal efficiencies improved, with mean removal efficiencies of 71% for Pb and 81% for Cr at the Dagenham wetland. An exception to this was for suspended solids which showed an overall increase of 99% during storm events. Several design and operational issues have been identified and addressed during the course of the monitoring programme, and recommendations for the improved design and operation of urban runoff treatment wetland systems have been made. A range of micro-organisms, isolated from both wetland systems, were able to tolerate elevated Zn and Pb concentrations. Two strains (Beauveria bassiana and Rhodotorula mucilaginosa) were selected for further work. Both strains could accumulate Zn and Pb, with B. bassiana showing a high capacity to bind Pb (maximum concentration of 136mgPb/g cells dry weight). Comparison of the growth of B. bassiana at 4°C and 30°C suggested that processes of microbial metal accumulation may occur throughout the year in treatment wetlands. The presence of Pb inside hyphae of B. bassiana, associated with hyphae walls and in the surrounding medium was confirmed. This study has found that micro-organisms isolated from urban runoff treatment wetlands can tolerate and accumulate Zn and Pb, and the application of these results to wetland treatment processes is discussed.

Abstract: On Canada’s Pacific Coast, forestry is integral to society. Although economically important, harvesting practices may alter source waters that originate in forested watersheds through changes in suspended solids (SS) and dissolved organic matter (DOM). Each of these metrics has the potential to degrade source water quality, which poses challenges for drinking water treatment. While harvest impacts on source waters are generally well understood, effects differ regionally due to variations in climate, topography, and soil characteristics. Research is therefore needed across different ecozones, and until now, few studies have focused on the Pacific Maritime. Within this ecozone, one question that remains is how the magnitude of change caused by recent forest harvest compares to the background spatiotemporal variation in source water quality, and how this impacts drinking water treatability. To assess these effects, I examined variation in stream water SS and DOM across different flow conditions in forested subwatersheds with contrasting forest harvest histories and diverse characteristics (e.g., topography, soil depth and clay content). This work was done on the east coast of Vancouver Island, British Columbia, in the Comox Lake watershed. Subwatersheds ranged greatly in size (0.21–214.08 km2) and mean elevation (371–1366 m above sea level). Total annual precipitation in the watershed averaged 2193 mm yr-1 between 1981 and 2019. Streams were sampled from April 2019 to March 2020 across synoptic (thirty sites sampled four times), seasonal (ten sites sampled ten times), and storm (four sites; two storm events captured) sampling campaigns. Synoptic and seasonal sampling were conducted during stable baseflow conditions, while storm sampling targeted peak flows. Samples were analyzed for turbidity, total SS, DOM carbon concentration (DOM-[C]), and DOM composition to evaluate source water quality, as well as disinfection by-product formation potentials (DBP-FPs) to infer drinking water treatability. Targeted water quality monitoring revealed that recent forest harvest did not overwhelm the background spatiotemporal variation of SS and DOM in a recovering landscape. Instead, storm event and seasonal changes in hydrology were the primary control on water quality (i.e., SS and DOM) and resultant DBP-FPs: each exhibited a greater change with seasonal and storm flows than across spatially distinct subwatersheds. This highlights that temporal (i.e., hydrologic) factors, rather than spatial ones (i.e., forest harvest and catchment characteristics), were key in driving variation in water quality and treatability. Temporally-driven changes in SS, DOM, and DBP-FPs were not amplified by forest harvest, which suggests weak anthropogenic influences on source waters in the region. Here, a muted response to recent harvesting may be attributed to forestry practices (i.e., slash removal) and the prevalence of second growth forests (i.e., historical harvest in this region). Although responses were subdued, water quality and treatability metrics did vary according to harvested area in the Comox Lake watershed; this highlights the necessity of evaluating the relative importance of forest harvest and flow conditions when assessing source waters. Overall, this study contributes to our understanding of spatiotemporal effects on SS, DOM, and DBP-FPs in forested Pacific Coast subwatersheds.

Abstract: The Athabasca River (AR) is the longest river in Alberta with a wide variety of natural and potential anthropogenic inputs. The purpose of this study was to quantify the spatial variation of trace element (TE) concentrations and forms in this aquatic system. Water samples were gathered along a 125-km stretch of the river and at three points across the river, in locations upstream, alongside and downstream from the industrial region. The samples were collected using the novel, metal-free sampling methods. With respect to water quality and the uptake/toxicity of trace elements, and to determine the biological significance of trace elements in the river, their size-based distribution amongst different colloidal forms (i.e. truly dissolved, primarily organic, and primarily inorganic) was measured in the dissolved fraction (i.e., < 0.45 µm by filtration). In addition, total concentrations of trace elements were normalized to that of thorium (Th) to determine the extent of enrichment relative to natural ratios in the earth’s crust.Differences in the concentrations of dissolved and total TEs were observed between the transects upstream, midstream, and downstream of industry, and on the east and west sides of the river. Total concentrations of Al, As, Co, Cu, Fe, Mn, Ni, Pb, Th, Tl, and V were significantly (p < 0.05) more abundant downstream of industry, compared to upstream. With the exception of As and Cu, these elements occurred predominantly in the particulate fraction (i.e. > 0.45 µm). Normalization to Th showed that no trace elements were enriched in the particulate fraction. In the dissolved fraction (< 0.45 µm), concentrations of As, Co, Cu, Ni, Pb, Re, and V were significantly (p < 0.05) more abundant downstream of industry. Within the dissolved fraction, Fe and Pb were found mainly as primarily inorganic colloids, while the other trace elements occurred predominantly in the mainly ionic/truly dissolved fraction (i.e., < ca. 1 kDa). The average concentrations of the investigated trace elements were far below the surface water quality guidelines in the Athabasca River. The PCA analysis indicated that tributaries contribute meaningful amounts of total and dissolved trace elements to the AR.

Using batch and stream recirculating flume experiments to compare and contrast one clayey sediment (Warden Ditch) and two analytical grade clay minerals (montmorillonite and kaolinite), the dynamic interactions between two aquatic stressors (suspended solids and nickel) were explored. Aldrich humic acid was incorporated to demonstrate the mitigating effects of dissolved organic carbon (DOC) on Ni toxicity. The flux of Ni between compartments (dissolved and sorbed) was quantified as a partition/distribution coefficient. The USEPA test organism Daphnia magna (neonates, < 24 h) was utilized to evaluate toxicity in dynamic non-renewal, short-term bioassays. Generally, toxicity showed a linear relationship with turbidity level. Conversely, sorption coefficients were experiment specific, making them difficult to predict and assess. Clay functioned as an adsorbent, scavenging Ni. Results support the hypotheses that solids and metals act as stressors in streams, DOC attenuates the toxicity of Ni, and Ni fluxes quickly between system compartments.

Land use change results in significant amounts of soil migrating into aquatic streams during storm events. This suspended sediment, even in the absence of adsorbed contaminants, may be a significant stressor to aquatic organisms. The data on ecological effects of suspended sediment has mainly focused on salmonids or ecosystem level consequences such as habitat alteration. Few studies have quantified physiologic effects of suspended solids on water column organisms. The purpose of this research was to determine the effects of suspended clay on Daphnia magna and Pimephales promelas. Results of 7 d toxicity tests with D. magna in natural and defined clay suspensions indicated LC50 values ranging from 5 mg/L to 75 mg/L with montmorillonite being more toxic than kaolinite. Gill Na+/K+-ATPase levels in P. promelas decreased as a function of exposure duration to 1,000 mg/L suspended montmorillonite. These results underscore the need to consider physical stressors in watershed risk assessment.

A study of sediment and zinc concentrations in stormwater from the Garlands Road outfall was carried out to gain an understanding of the effects these two contaminants have on water quality in the Heathcote River and to investigate if any relationship existed between the two contaminants. Sampling was undertaken at three sites, the Garlands Road stormwater outfall and two sites on the Heathcote River, one upstream of the outfall beside the Garlands Road Bridge and another approximately 103 metres downstream of the outfall. Sampling was carried out during four separate storm events at low tide. Two sampling runs were undertaken within the first hour of a storm event to represent contaminant loadings in the first flush while the other sampling runs were conducted at two hours and five hours into a storm event respectively. Sampling was undertaken using the grab sample technique and the samples were analysed for suspended solids and zinc by the Environment Canterbury Water Laboratory. The results of the study found suspended solid concentrations from the stormwater outfall were up to twenty times higher than the suspended solid concentrations in the Heathcote River. Suspended solid concentrations were higher during the 'first flush' period when compared to samples taken outside this period. There appeared to be little impact on the downstream suspended solid concentrations as a result of the discharges from the Garlands Road stormwater outfall. Overall the suspended solid concentrations in the Lower Heathcote River were low, being between 13 and 67mg/L at all sites, despite the dirty appearance of the water in the study area. Zinc levels followed the same trend as suspended solids being substantially higher in the stormwater samples than in the river samples. There was little noticeable difference in upstream results compared with downstream, despite the influence of high loadings from the Garlands Road stormwater outfall. Overall zinc levels in the stormwater were higher than typical urban stormwater and in the Heathcote River itself zinc levels on two of the four sample days breached the Australia New Zealand Environment and Conservation Council guidelines for zinc concentrations in a highly modified ecosystem. The correlation between suspended solids and zinc showed a strong positive relationship based on the small number of samples taken. This supports other research that has found direct relationships between suspended solid loadings in urban runoff and heavy metals. The stormwater network was investigated using drainage maps from the Christchurch City Council. This study found only one site in the catchment with any form of stormwater treatment. All other stormwater discharged untreated from hardstand areas and roofs into the reticulated network and then into the Heathcote River.

The aquaculture industry has experienced a great expansion in recent years. Along with this growth, increased regulatory attention has been directed towards aquacultural effluents. The problem with the majority of these discharges is the solids and nutrient spikes that occur during times of high farm activity. Several studies have proven that these discharges have the potential to adversely affect downstream water quality. Although several treatment options are currently in use, the use of Best Management Practices (BMPs)has been recommended in recent years to improve the quality of these discharges. The implementation of one of these BMPs, the use of a high energy feed, was the focus of this study. In two separate experiments at trout raising facilities, the effluents of basins receiving a high energy feed were compared to similar basins receiving a standard trout grower feed. The water quality parameters of main concern were total suspended solids, total Kjeldahl nitrogen (TKN) and total ammonia nitrogen (TAN). The results of these studies showed that the effluents of basins receiving a high energy feed generally contained significantly lower concentrations of TSS, but higher amounts of TKN than those receiving a standard grower feed.

Three suspended solids types containing a range of physicochemical characteristics were used to determine the effect of suspended solids on the bioavailability of acenaphthene, 1,2,4,5-tetrachlorobenzene, zinc, and chlordane to Daphnia magna and Pimephales promelas. Generally, the bioavailability of zinc and chlordane decreased due to interactions with all suspended solids types while bioavailability of acenaphthene and 1,2,4,5-tetrachlorobenzene were not clearly reduced. Partition coefficients and slope of dose-response curves related chemical characteristics and organism sensitivity, respectively, to experimentally determined results. It is believed that the biologically available form of these chemicals to Daphnia magna and Pimephales promelas resides in the aqueous phase.