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An examination of shallow GAC filter caps to promote biological filtration without requiring costly full filter bed media replacements.

Microfiltration (MF) and ultrafiltration (UF) consistently remove suspended material and pathogens from drinking water; however, membrane fouling inhibits their application by increasing operation and maintenance costs. Coagulation/flocculation is a commonly used pretreatment method for the reduction of membrane fouling; in this review it has been grouped into three typical configuration types: Type 1: coagulation + no/incidental flocculation, Type 2: coagulation + flocculation, and Type 3: conventional coagulation, based on operational conditions. The impact of each configuration on floc properties, membrane fouling, and organics removal has been reviewed in detail. Due to relatively high membrane resistance and low NOM reductions, configuration Type 1 may not be optimal for fouling control and organics removal when compared to Types 2 and 3. Configuration Type 2 led to the lowest cake layer and specific cake layer resistance for both MF and UF, while there is evidence that Type 3 results in the greatest reduction in fouling rate by reducing mass flux towards the membrane surface. As expected, with no coagulant results indicate that UF achieves greater organics removal when compared to MF, but with the addition of coagulant performance is similar for all configuration types. By highlighting the connection between coagulation/flocculation configuration types and membrane performance, the review provides insight for the design and operation of pretreatment for low pressure membrane filtration. In addition, understanding the impact of configuration types on floc properties aids in revealing the fouling mechanisms that dictate membrane performance. Knowledge gaps have been identified for guidance on future research.

Application of real-time fluorescence excitation emission matrices (EEM) as a tool for water quality assessment was investigated. A bench-scale fluorescence system with on-line monitoring capabilities was used to quantify several polycyclic aromatic hydrocarbons (PAHs) and pesticides in surface waters of Ontario, Canada. Parallel factors analysis (PARAFAC), an unsupervised multi-way analysis approach, was compared to a supervised peak-picking approach. Both approaches produced sensitive regression models capable of predicting contaminant concentration with mean absolute errors (MAE) that ranged from 0.032 to 0.293 μg L−1 for lake water, and 0.052 to 0.921 μg L−1 for river water. In addition, results showed accurate detection of contaminant concentrations exceeding 0.25 μg L−1. However, concentration and variability of natural organic matter (NOM) in natural waters presented unique challenges to peak-picking, PARAFAC, and regression analysis, which were mitigated by expert supervision as well as site-specific and timely calibration.

MX precursor removal was compared at pilot-scale in continuously and cyclically operated biofilters with empty bed contact times (EBCTs) of 15 and 30 minutes. Water and filter media samples were collected under ambient water quality conditions and during a spike of 7 mg L−1 humic acid (HA). MX formation potential (FP) removals ranged from 26 to 49% and 45 to 61% under ambient precursor and spiked conditions, respectively, suggesting that biofiltration was capable of removing or altering MX precursors. Removal was very strongly correlated (R = 0.90) with ATP (a measure of biomass density) for all trials. MX FP reduction was significantly higher (p < 0.05) with respect to biomass density when comparing cyclically vs. continuously operated filters for all trials. Although lower average ATP concentrations were observed for the cyclically operated filters, these filters achieved a greater MX FP reduction per unit biomass which implies a higher rate of biological function. EBCT did not impact biofilter performance when considering MX FP reduction with respect to either filter depth or biomass density.

Quantitative microbial risk assessments (QMRA) was conducted for 10 drinking water facilities located in Canada. Monthly risk estimates were based upon a suite of reference pathogens for the raw water, as well as detailed process assessments that considered the variability treatment at individual treatment facilities. The majority of the facilities (9 out of 10) maintained risk levels significantly below the World Health Organization's target of 10−6 DALY per person per year. Cryptosporidium was shown to be the most significant contributor for microbial risk at all locations. Potential treatment specific failure scenarios were evaluated; most treatment facilities were capable of withstanding partial filtration and disinfection failures as a result of the multi-barriers employed.