Impact of Operational and Design Parameters on Natural Organic Matter Removal and its Correlation with NDMA Precursor Removal or Formation during Biofiltration in Drinking Water Treatment

NOM is a complex mixture of organic compounds that are present in all natural waters and is mainly originating from plant and aquatic organism degradation products. Therefore, the specific composition of NOM is site-specific. Removing NOM during drinking water treatment is very beneficial, since NOM not only causes aesthetic problems, such as taste, odour, and colour problems, but also impacts other treatment processes. NOM, for examples, causes increased coagulant and disinfectant demands; contributes to corrosion and bacterial regrowth throughout the distribution system; transports metals and hydrophobic chemicals; and interferes in adsorption processes of other contaminants. However, one of the most important points for removing NOM is that NOM fractions have been identified as being precursors to potentially carcinogenic disinfection by-products (DBPs). The goal of this research was to identify the impact of different operational, design, and water quality parameters on the characteristics and removal of NOM fractions during bench-scale and pilot-scale biofilter columns at different drinking water treatment plants (DWTPs). Parameters investigated in bench-scale biofilter columns at three different facilities (Facilities B, I, and L) include: water sources, media acclimated/operated in different water sources, and pre-ozonation. During these bench-scale experiments, three different biofilter media (from Facilities B, I, and L media) were tested simultaneously at each of the three facilities. Also, two different pilot-scale experiments were carried out, one at Facility C, which investigated the following parameters: media type, backwash type, and ammonia addition. The other pilot-scale experiment was at Facility Q, which investigated the following parameters: full-scale treatment processes prior to biofiltration, media type, backwash type, and backwash frequency. At both the pilot-scale facilities, the biofilter profiles and kinetics of the NOM fraction removals for the different parameters were also investigated. Lastly, the NOM fraction removals from both the bench-scale and pilot-scale experiments were correlated to the NDMA precursor removals or formations. The NOM fractions in this research were characterized by using two relatively new NOM characterization techniques: LC-OCD and fluorescence excitation emission matrix (FEEM). LC-OCD separates NOM into five different fractions based on molecular weight size, and these fractions are: biopolymers (BP), humics (HS), building blocks (BB), low molecular weight (LMW) acids/humics, and LMW neutrals. FEEM detects molecules that contain fluorophores and it can therefore identify three different fractions: humic acids (HA), fulvic acids (FA), and protein-like materials. Furthermore, the NDMA concentrations in this research was analysed using a measuring technique called uniform formation condition (UFC). UFC mimics average chloramination conditions used at DWTPs across North America. The bench-scale experiments at Facilities B, I, and L showed that when all the different media acclimated/operated in different water sources were fed the same water source they behaved very similarly in terms of NOM fraction removal and water sources therefore matters. However, when the same media was fed the water sources from each of these facilities, then there were barely any similarities and the media acclimated/operated in different water sources therefore barely had any influence. Also, the pre-ozonation at Facility B improved the NOM fraction removals when combined with the bench-scale biofiltration columns. The pilot-scale experiments at Facilities C and Q showed that powdered activated carbon (PAC) drastically removed various NOM fractions, it, for example, successfully removed more than 83% of BP. Also, granular activated carbon (GAC) media was the media type that had the best removals of various NOM fractions at both pilot-scale facilities. At facility C, the chloraminated backwashed columns had higher removals of DOC (4.3 percentage points higher), BP (20 percentage points higher), LMW acids/humics (3.9 percentage points higher), and LMW neutrals (11 percentage points higher) than the GAC control columns. However, at Facility Q there were no noticeable differences between backwash types or backwash frequencies on the NOM removals, due to low removals at most sampling events. These low removals made it difficult to assess conclusively the influence from these parameters on NOM fraction removals. At Facility C, only DOC, BP, and HS relatively fitted the kinetics models, and the best data fit was for BP. At Facility Q, BP during phase 1 and DOC for only one column during phase 2 poorly fitted the kinetics models. However, there were no clear trends regarding which reaction order fitted each fraction removal the best. The reason is that the change in the coefficients of determination (R2 coefficients) only marginally changed from 0th to 2nd order model. Also, these poor fits between NOM fraction removals and kinetics models is due to, for example, only 4-5 data points for each profile and only low removals across the biofilters. For the NDMA UFC, pre-ozonation at facility B also substantially reduced NDMA UFC, and pre-ozonation combined with biofiltration had the lowest NDMA UFC concentrations. Softening also substantially increased NDMA UFC at the full-scale treatment process at Facility Q. Last, there was a statistically significant correlation between higher protein-like materials intensities as measured by FEEM in the biofilter influents and higher NDMA UFC concentrations in the biofilter influents. The same was also observed for the biofilter effluents. This research provides greater insight into NOM fraction removals, biofiltration performance, and the correlation between NOM and NDMA UFC. Although the results might be site-specific, these results indicated that to optimize the NOM fraction removals at a DWTP PAC, pre-ozonation, and GAC media in the biofilters should be employed. Also, to minimize NDMA precursor formation during drinking water treatment, pre-ozonation prior to the biofilters should be employed, but softening should be avoided. These findings provide insight to municipalities, consultants, and staff members at DWTPs on some operational and design parameters that should be taken into consideration when designing or upgrading a DWTP

Early childhood portfolios as a tool for enhancing learning during the transition to school

From 2005-2008 Mangere Bridge Kindergarten in New Zealand carried out a Centre of Innovation research project exploring the transition between early childhood education and school. A flexible action research approach was used, with the three teacher researchers, supported by two university research associates, developing and researching a range of strategies for supporting children’s learning as the children and their families ‘crossed the border’ from early childhood education to school. Many of these initiatives involved working closely with teachers in the local school setting. This paper focuses on one aspect of the findings, the ways in which the early childhood portfolios could be used to enhance children’s learning during the transition to school. Portfolios were identified as a belonging and empowerment tool; a means for school teachers to access to children’s funds of knowledge; playing a role in constructing a positive self-image about learning; and as valuable literacy artefacts

LED receiver impedance and its effects on LED-LED visible light communications

This paper experimentally demonstrates that the AC impedance spectrum of the LED as a photodetector heavily depends on the received optical power, which may cause the impedance mismatch between the LED and the post trans-impedance amplifier. The optical power dependent impedance of the LED is well fitted by a modified dispersive carrier transport model for inorganic semiconductors. The bandwidth of the LED-LED visible light communication link is further shown to decrease with the optical power received by the LED. This leads to a trade-off between link bandwidth and SNR, and consequently affects the choice of the proper dada modulation scheme.Comment: 9 pages, 9 figures, submitted to Optics Expres

Flexibility between market-led and government-led economies

The 1997-98 East Asia financial crisis has raised doubts over the roles of two economic-systems: market-led and government-led economies. This paper deliberates on the two opposing economic systems: the choice of which are continually debated. There is a need for governments to look at economic flexibility and determine whether the countries affected by the financial crisis could reposition themselves fast enough. More specifically, this paper evaluates the performance of government-led economies such as those in Malaysia,Singapore, Thailand, Philippines, and Indonesia when compared to marketled economies as practised in the United Kingdom, United States, and Japan.A compilation of an index method based on Angresano (1996) consisting of the quantitative performance measure for an identified country was computed over the average period 1980-2003. The findings of this study suggest that the approaches to a market-led or government-led economy is a matter of degree and are not mutually exclusive

Household survey to evaluate the Zambia-led Prevention Initiative: Baseline report

With an estimated HIV prevalence of 14.3 percent among men and women age 15–49, Zambia is one of the sub-Saharan African countries most affected by the HIV and AIDS pandemic. The Zambia-led Prevention Initiative Program (ZPI) was developed by a consortium led by FHI360, with the Population Council as the evaluation partner. This study determined baseline levels of key indicators related to HIV, gender-based violence, and reproductive health. Additionally, the baseline findings provide critical insights into key areas for interventions in Zambia and highlights variability in the populations across provinces and between males and females that provide valuable guidance for programming

Further studies on <i>Tabanus claripennis</i> (Bigot) with special reference to the morphology and biology of the pre-imago stages

Se realiza la descripción de larvas de Tabanus claripennis (Bigot) halladas en La Plata (R. A.) y de las pupas obtenidas en el laboratorio.Larvae of Tabanus claripennis (Bigot) collected in La Plata (R. A.) and the pupae thus obtained in the laboratory are described with special reference to the biological characteristics of the pre-imago stages.Facultad de Ciencias Veterinaria

Further studies on <i>Tabanus claripennis</i> (Bigot) with special reference to the morphology and biology of the pre-imago stages

Se realiza la descripción de larvas de Tabanus claripennis (Bigot) halladas en La Plata (R. A.) y de las pupas obtenidas en el laboratorio.Larvae of Tabanus claripennis (Bigot) collected in La Plata (R. A.) and the pupae thus obtained in the laboratory are described with special reference to the biological characteristics of the pre-imago stages.Facultad de Ciencias Veterinaria

Nurse led care

What's the difference between medical and nursing care? The answer is not straightforward, but shortages in the medical workforce mean that nurses are increasingly called on to undertake work that was previously done by doctors (such as undertaking surgery,1 prescribing drugs, performing triage in emergency departments), whereas shortages in the nursing workforce mean that healthcare assistants now do many tasks that nurses are trained to do. This fluidity in professional roles and competencies enables the health workforce to respond to need, but are outcomes for patients being improved? Do these benefits come at an additional cost, and if so, are they worth paying for

From Tutor-led to Student-led design education: the Global Studio

“Tutor-led” design education has been argued to be a system where lecturers are at the centre of teaching & learning activities and where educators’ tastes strongly influence students’ outcomes. Design education has also been argued not to prepare graduates for working in highly complex professional capacities synonymous with the contemporary era. We argue the role of tutors in tutor-led design education to be a factor in this. The Global Studio runs Web 2.0 enabled industry sponsored international collaborations between students. One aim is to introduce learners to “complex project situations” and consequently to prepare them for contemporary working life. It is operationally different from “tutor-led” design education as lecturers are more “distant” in teaching &learning activities and students construct conversations and outcomes primarily via interaction with peers. Feedback from home-institution students suggests many individuals struggle with making decisions without “tutor-led design education” involvement from tutors. Given the on-going change in funding provision and the continuing dissolution of “normal” structures, universities are predicted to continue to undergo extensive transformation in their remit and the way education is delivered. We ask whether tutor-led design education is maintainable and whether educators and students are prepared for the consequences of change