Caetano C. Dorea

Effects of Temperature and pH on Reduction of Bacteria in a Point-of-Use Drinking Water Treatment Product for Emergency Relief

ABSTRACT The effects of temperature and pH on the water treatment performance of a point-of-use (POU) coagulant/disinfectant product were evaluated. Cold temperatures (∼5�C) reduced the bactericidal efficiency of the product with regard to Escherichia coli and total coliform log10 reductions.

Treatment of heavy metals by iron oxide coated and natural gravel media in Sustainable urban Drainage Systems

Sustainable urban Drainage Systems (SuDS) filter drains are simple, low-cost systems utilized as a first defence to treat road runoff by employing biogeochemical processes to reduce pollutants. However, the mechanisms involved in pollution attenuation are poorly understood. This work aims to develop a better understanding of these mechanisms to facilitate improved SuDS design. Since heavy metals are a large fraction of pollution in road runoff, this study aimed to enhance heavy metal removal of filter drain gravel with an iron oxide mineral amendment to increase surface area for heavy metal scavenging. Experiments showed that amendment-coated and uncoated (control) gravel removed similar quantities of heavy metals. Moreover, when normalized to surface area, iron oxide coated gravels (IOCGs) showed poorer metal removal capacities than uncoated gravel. Inspection of the uncoated microgabbro gravel indicated that clay particulates on the surface (a natural product of weathering of this material) augmented heavy metal removal, generating metal sequestration capacities that were competitive compared with IOCGs. Furthermore, when the weathered surface was scrubbed and removed, metal removal capacities were reduced by 20%. When compared with other lithologies, adsorption of heavy metals by microgabbro was 10-70% higher, indicating that both the lithology of the gravel, and the presence of a weathered surface, considerably influence its ability to immobilize heavy metals. These results contradict previous assumptions which suggest that gravel lithology is not a significant factor in SuDS design. Based upon these results, weathered microgabbro is suggested to be an ideal lithology for use in SuDS.

The Relationship between Microbial Community Evenness and Function in Slow Sand Filters

ABSTRACT Two full-scale slow sand filters (SSFs) were sampled periodically from April until November 2011 to study the spatial and temporal structures of the bacterial communities found in the filters. To monitor global changes in the microbial communities, DNA from sand samples taken at different depths and locations within the SSFs and at different filters ages was used for Illumina 16S rRNA gene sequencing. Additionally, 15 water quality parameters were monitored to assess filter performance, with functionally relevant microbial members being identified by using multivariate statistics. The bacterial diversity in the SSFs was found to be much larger than previously documented, with community composition being shaped by the characteristics of the SSFs (filter age and depth) and sampling characteristics (month, side, and distance from the influent and effluent pipes). We found that several key genera (Acidovorax, Halomonas, Sphingobium, and Sphingomonas) were associated with filter performance. In addition, at the whole-community level, a strong positive correlation was found between species evenness and filter performance. This study is the first to comprehensively characterize the microbial community of SSFs and link specific microbes to water quality parameters. In doing so, we reveal key patterns in microbial community structure that relate to overall community function. IMPORTANCE The supply of sustainable, energy-efficient, and safe drinking water to an increasing world population is a huge challenge faced by the water industry. SSFs have been used for hundreds of years to provide a safe and reliable source of potable drinking water, with minimal energy requirements. However, a lack of knowledge pertaining to the treatment mechanisms, particularly the biological processes, underpinning SSF operation has meant that SSFs are still operated as “black boxes.” Understanding these dynamics alongside performance-induced effects associated with operational differences will promote optimized SSF design, maintenance, and operation, creating more efficient and environmentally sustainable filters. Through a spatial-temporal survey of full-scale SSFs at various points of operation, we present the most detailed characterization to date of the functional microbial communities found in SSFs, linking various taxa and community metrics to optimal water quality production. The supply of sustainable, energy-efficient, and safe drinking water to an increasing world population is a huge challenge faced by the water industry. SSFs have been used for hundreds of years to provide a safe and reliable source of potable drinking water, with minimal energy requirements. However, a lack of knowledge pertaining to the treatment mechanisms, particularly the biological processes, underpinning SSF operation has meant that SSFs are still operated as “black boxes.” Understanding these dynamics alongside performance-induced effects associated with operational differences will promote optimized SSF design, maintenance, and operation, creating more efficient and environmentally sustainable filters. Through a spatial-temporal survey of full-scale SSFs at various points of operation, we present the most detailed characterization to date of the functional microbial communities found in SSFs, linking various taxa and community metrics to optimal water quality production.

Bulk water treatment unit performance: For the cameras or the community?

As humanitarians we must be deeply concerned about using the most effective solutions for saving lives and reducing morbidity, whilst working within reasonable cost envelopes. In this respect it is critical to place the brightest spotlight upon the practice of using bulk water treatment units (BWTU), as witnessed most recently on a massive scale in the Pakistan floods of 2010. There, as in other huge crises, many BWTUs were deployed by donors and other agencies, sometimes as a knee-jerk reaction to an overwhelming crisis. These appear to offer neat ‘plug and play’ solutions that also happen to be very media friendly. However, some of the BWTUs sent to flood-affected areas of Pakistan in 2010 demonstrate that there is an absence of appropriate selection criteria for BWTUs and the significant limitations on their use are not fully understood. Though the evidence gathered is partial, there is enough to suggest that some agencies are engaging in poor practice.

Cross-country analysis of faecal sludge dewatering

ABSTRACT Dewatering of faecal sludge (FS) is indispensable for adequate FS management. However, comprehensive knowledge is lacking on FS dewatering performance. This study compared the dewatering performance of FS from different countries and onsite sanitation technologies, to assess influential characteristics on dewatering, and to compare dewatering performance of FS with wastewater sludge. We collected 73 FS samples from septic tanks, lined pit latrines, unlined pit latrines and johkasou tanks in Uganda, Vietnam and Japan, and 18 samples of wastewater sludge in Switzerland. Capillary suction time (CST) and total solids (TS) of centrifuged sludge (%TSfinal) were determined as metrics of dewatering rate and dewaterability, respectively, together with relevant sludge characteristics. Data were analysed by bootstrapping comparison of median results of each sample category and by bootstrapping multiple regression analysis to quantify the relative importance of sludge characteristics on dewatering performance. Results showed that the dewatering rate was significantly different between FS from different technologies, whereas dewaterability was significantly different within the same technology. FS had a significantly lower dewatering rate than wastewater sludge. In contrast, FS dewaterability was greater than wastewater sludge. However, this could be attributed to higher concentrations of sand in FS. Electrochemical properties such as NH4-N and surface charge had the strongest correlation to dewatering rate, and solid properties such as sand content and total volatile solids to dewaterability. The results identify potential characteristics that could explain and predict the high variability of FS dewatering performance that is observed in the field.

Influence of biofilms on heavy metal immobilization in sustainable urban drainage systems (SuDS)

This paper physically and numerically models the influence of biofilms on heavy metal removal in a gravel filter. Experimental flow columns were constructed to determine the removal of Cu, Pb and Zn by gabbro and dolomite gravel lithologies with and without natural biofilm from sustainable urban drainage systems (SuDS). Breakthrough experiments showed that, whilst abiotic gravel filters removed up to 51% of metals, those with biofilms enhanced heavy metal removal by up to a further 29%, with Cu removal illustrating the greatest response to biofilm growth. An advection–diffusion equation successfully modelled metal tracer transport within biofilm columns. This model yielded a permanent loss term (k) for metal tracers of between 0.01 and 1.05, correlating well with measured data from breakthrough experiments. Additional 16S rRNA clone library analysis of the biofilm indicated strong sensitivity of bacterial community composition to the lithology of the filter medium, with gabbro filters displaying Proteobacteria dominance (54%) and dolomite columns showing Cyanobacteria dominance (47%).

Simple improvements for emergency batch water treatment

Batch water treatment consists of the intermittent use of settling tanks for water clarification, and is a common treatment practice during emergency relief efforts. This article presents simple improvements to coagulant dosing and water quality based on experience gained in the aftermath of the 2005 South Asian earthquake.

Decision-making scheme for disinfection by-product monitoring intended for small drinking water systems

Trihalomethanes (THMs) and haloacetic acids (HAAs) are the most prevalent disinfection by-products (DBPs) in drinking water and their occurrence is regulated in several countries. However, most DBPs are not regulated, even though some may have greater toxicological relevance than regulated DBPs. Small water systems (SWS) supplied by surface waters are vulnerable to high levels of DBPs due, primarily, to a lack of adequate treatment processes that remove DBP precursors. Moreover, monitoring DBPs is difficult for SWS because it requires good knowledge of the system and qualified operators to select locations and periods for sampling. In view of the above, this study focuses on the development of a decision-making scheme for DBP monitoring in SWS, for the appropriate identification of periods and locations for DBP sampling. The study is based on information generated in 25 small systems in Canada. The following DBPs were considered: four THMs, five HAAs, four haloacetonitriles, two haloketones and one halonitromethane. The comparison of various sampling scenarios that took account of the temporal variability of DBPs served to identify appropriate periods for DBP sampling. Residual chlorine demand was used as an indicator of the spatial variability of DBPs in order to identify appropriate locations for sampling. This decision-making scheme provides SWS operators with a high cost-benefit tool for decision making to select sampling periods and locations in order to comply with current regulations concerning THMs and HAAs (and eventual future regulations for non-regulated DBPs).

Landscape of WASH-relevant Training for Humanitarian Emergencies.

Background: Both employed humanitarian personnel as well as those seeking to start a career as an aid worker are often provided with or seek training on the theme of humanitarian water, sanitation, and hygiene (WASH). The objective of this study was to conduct a landscaping exercise of the available WASH-relevant training for humanitarian emergencies. Methods: An open internet search was performed with specific terms related to humanitarian WASH. Retained search results included those training opportunities (including past ones) that were themed around or with a mentioned relevance to humanitarian WASH. Results and Discussion: A total of 42 training courses relevant to humanitarian emergency WASH were retained. In addition to the more generic/introductory trainings, some provided thematic variations such as coordination of WASH responses, project management, risk reduction, information, education and communication (IEC), and complex emergencies. Timely topics such as urban WASH, Ebola, and WASH innovations were also observed indicating the responsiveness of the training providers to the changing needs of humanitarian WASH response programmes. This survey also revealed a large variety in terms of target audience, duration, fees, location, and language of courses. There was no centralised listing of courses available on the Internet. Limitations of this exercise were also discussed.

Aluminium residuals in emergency water treatment: What you wanted to know, but never asked

Alum is widely used in water treatment because of its many advantages, of which its relative low cost and worldwide availability have ensured it to be the coagulant of choice for emergency water treatment. However, in certain circumstances, its use may leave an undesirable coagulant aluminium residual in the finished water. Such residuals can generate (unwarranted) fear over the use of this useful coagulant (particularly among the misinformed). This article is focused on clarifying topics related to aluminium residuals, such as its occurrence, health risks, significance in emergency water treatment, measurement, and control strategies. These issues are discussed in view of the practical constraints faced in the field during emergencies and where appropriate contrasted with conventional (non-emergency) practice. Emergency water treatment sludge disposal and alternative coagulants to alum are also addressed.