Environmental Science: Water Research & Technology blog

The answer is fortunately no, based on the findings of a recent article published in Environmental Science: Water Research and Technology.

Drinking water distribution systems (DWDS) rely on the use of disinfecting agents to prevent the outbreak of diseases carried by waterborne pathogens. A commonly employed chemical agent is free chlorine, however health risks associated with the production of disinfection by-products (DBPs) have favoured the use of chloramines as secondary disinfectants. Chloramines provide longer lasting levels of residual disinfectant, but leave the system prone to nitrification, a process which can affect drinking water quality. Nitrification, and the so-called ‘chlorine burns’, treatments used to rectify the system, are considered disturbances to the microbial communities which populate a DWDS and have been linked to the development of pathogenic microbial agents and the spread of antibiotic resistance genes (ARGs).

Graphical Abstract

The present study operated a simulated drinking water distribution system through the typical phases of: normal operation, failure (i.e. nitrification), and rectification in order to study the microbiome and its response to the mentioned disturbances. Under normal operation the bacterial community revealed itself to be complex, with a small number of dominant species (the core microbiome) accompanied by a great number of species which together comprise only a small portion of the community (the rare biosphere).

The drastic changes in DWDS conditions realised during progression through the various operational phases allowed for the study of the conditionally rare taxa (species normally present in low abundance, but which become dominant under certain conditions). For example, the nitrifier Nitrospira spp., present in very low abundance or under the detection limit during normal operation with chloramine disinfectant, becomes present to noticeable levels during system failure. Nitrification is associated with the accelerated decay of chloramine which makes it difficult to maintain appropriate disinfectant levels under failure conditions and offers an opportunity for certain pathogens to multiply. One such pathogen, Legionella pneumophila, is over 10 times more abundant in free-chlorine treated water in the absence of secondary chloramine disinfectant. Such observations suggest that monitoring of conditionally rare taxa could predict nitrification in chloraminated DWDSs and help prevent potential dangerous situations in which public health becomes threatened by waterborne pathogens.

Genome analysis for a number of isolates from the core microbiome revealed the presence of a large number of gene clusters (165) with similarity to known ARGs. Combined these could offer their hosts resistance to a broad range of antibiotics such as: erythromycin, ciprofloxacin, tetracycline, rifampin, fluoroquinolone, and others. Transfer of these genes to human-related bacteria is noted as being highly unlikely though, and any antibiotic resistance conferred to be limited to the host organism. The study also considered the effect of disturbances on the biofilm populations of the DWDS; previously biofilms had been described as reservoirs of antibiotic resistant bacteria, but with little information being available on their role in the spreading of antibiotic resistance within DWDSs. Three strains of M. chelonae were selected from the biofilm for genomic analysis following disturbance events. The genome was found to be conserved throughout the operational stages with no changes in the ARG ensemble either, in contrast to the expectations of selection pressure causing mutations.

Finally, the microbial community proved to be resilient returning back to its initial state during the second normal operation phase. In conclusion, the study analysed both the dominant and minor bacterial components in the DWDS ecosystem, and monitored their response to changes in physicochemical properties of the environment. This showed how opportunities arise for the spread of waterborne pathogens, but found no evidence for the development of antibiotic resistance within the DWDS system.

To read the full article for free* click on the link below:

Resilience of microbial communities in a simulated drinking water distribution system subjected to disturbances: role of conditionally rare taxa and potential implications for antibiotic-resistant bacteria
V. Gomez-Alvarez, S. Pfaller, J. G. Pressman, D. G. Wahman and   R. P. Revetta
Environ. Sci.: Water Res. Technol., 2016, Advance Article
DOI: 10.1039/C6EW00053C

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About the webwriter

Dan Mercea is a PhD student in the Fuchter group at Imperial College London. He is working on developing enantioselective FLP catalysis.

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*Access is free through a registered RSC account – register here

In a Perspective article recently published in Environmental Science: Water Research & Technology, Englehardt et al. discuss a new vision for municipal water management: Net-zero water (NZW), a system which aims at neither importing nor exporting water from the service area – a way forward for local water independence.

Even though water availability is high in many regions, many people are still lacking access to energy-inexpensive, clean water. There are several stressors affecting water resources. Increasing demand for clean water can be attributed to several global and local processes operating on different scales and with varying impact, such as industrialization, rapid population growth, climate change and environmental degradation. We are facing a grand challenge: a resource-constrained world where we need to make water management more sustainable.

Net-zero water management – a new paradigm for water management

A NZW system is a management water and wastewater scheme that neither withdraws nor releases significant flows of water outside of its service area, ranging from a single residential lot to a large urban water district. NZW management proposes that high-demand and high-population areas, such as urban areas, no longer consume water needed by downstream regions, nor depend on upstream regions for supply.

One main motivation for net-zero municipal water management, besides prevention of water shortages, is that it aims to be energy-positive; this means that it should retain and save more hot-water thermal energy in the water than the energy used for treatment processes. Consequently, there is a demand to decrease the energy demands from water and disposal of wastewater containing hot water thermal energy.

NZW management can be operationalized in almost any modern catchment basin through the use of direct potable reuse (DPR). With this method, recycled water is introduced into the raw water supply directly upstream of a water treatment plant without passing through a reservoir or aquifer (environmental buffer) or introduced directly into a potable water supply distribution system. These systems show good economic capacities in producing potable water from municipal wastewater.

A schematic of a contemporary water management compared to the vision of a Net-Zero treatment process from a household perspective.

From buzzword to business: where do we go from here?

Net-zero water management is first and foremost a new vision, although it is becoming practical and technologically achievable to reuse water via a wide range of applications. Current implementations may not be easily reproduced in the near future, especially outside of research and demonstration settings. The authors conclude that there are several important targets and goals that we need to consider for reaching proper implementation of NZW; there is a demand for regulatory standards, policies and commercialized technologies to take the steps from vision to operation, and to a wider adoption of NZW systems.

Public acceptance is key for implementation of NZW systems

Governing structures and regulatory processes require time to develop, and regulatory infrastructure is crucial for the development of cost-effective commercial equipment, hence public acceptance and engagement in NZW is vital for proper implementation of NZW systems, as stated authors state.

Do you have ideas or visions on how to further develop Net-zero water management? Are there other important factors to consider that the authors did not discuss? Please share your opinions by commenting below after you have read the paper for free*:

Net-zero Water management: achieving energy-positive municipal water supply
J. Englehardt, T. Wu, F. Bloetscher, Y. Deng, P. Pisani, S. Eilert, S. Elmir, T. Guo, J. Jacangelo, M. LeChevallier, H. Leverenz, E. Mancha, E. Plater-Zyberk, B. Sheikh, E. Steinle-Darling and G. Tchobanoglous.
Env. Sci: Water Res. Technol. 2016, Advance Article
DOI: 0.1039/C5EW00204D

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About the webwriter:

Jesper Agrelius is a MSc student in Environmental Science at Linköping University, Sweden. His main interests regards environmental science, especially climate change and biogeochemistry. You can follow him on Twitter @JesperAgrelius.

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*Access is free through a registered RSC account.

There is a critical need for inexpensive point-of-use methods (POU) for purifying drinking water in developing countries to prevent waterborne pathogens.

Microbial contamination of water causes the spread of avoidable water-borne diseases, such as cholera, giardiasis, gastroenteritis and cryptosporidiosis, highlighted by WHO in their guidelines for drinking water quality. The potential health consequences of microbial contamination are important to consider and may never be compromised, from catchment to customer.

Figure 1. Examples of pathogenic microorganisms in contaminated surface water (left)
and the effect of nano-enabled (AG or CU NP) paper filters on the contaminated water (right).

Drinking water quality in Limpopo, South Africa

The last 20 years have showed an increase in drinking water quality for South Africa, where 95% of the population are considered to have access to potable drinking water as of 2012. However, a lot of rural residents still do not have reliable access to potable water and Limpopo, the study area in a recently published article, is the most rural province in South Africa. This region is highly affected by a lack of potable water and as a result the rates of diarrhoea cases are much higher than the national average.

Silver and copper – ‘noble’ in many ways

For the first time in the field, a study by Dankovich et al., published in Environmental Science: Water Research & Technology, demonstrates a novel and affordable technology for purifying drinking water. By using nano-enabled paper filters as a point-of-use method, the filters effectively inactivated coliform bacteria from contaminated water sources in Limpopo, South Africa.

The microbial water quality was improved by passing contaminated surface water from rural areas through nanoparticle paper filters which contained either AgNP (silver nanoparticles) or CuNP (copper nanoparticles). All of the AgNP and CuNP paper filters prominently reduced total coliform and E. Coli as compared to the untreated influent water, and E. coli bacteria were eliminated for the rural and urban medium samples.

Figure 2. Blotter papers (a) untreated, (b) with silver nanoparticles, and (c) with copper nanoparticles.
Note the scale: each paper is 6.5 cm by 6.5 cm and the filter cross section is 4.7 cm by 4.7 cm.

The problem of microbial contamination of water, turbidity and other pollutants from the natural sources studied in this specific research project are representative of many similar settings in the developing world and these filters show great promise as a water purifying option for resource-limited countries and regions.

The researchers raise important future directions for further development in the area are water purification by nano-enabled paper filters as a point-of-use method. Future research is needed to evaluate the design of practical and user-friendly filter holders, as well as address the practical challenges of implementing this paper filter technology in emergency/disaster relief settings and rural households.

Explore the exciting research regarding the nanoparticle paper filters in detail for free*:

Inactivation of bacteria from contaminated streams in Limpopo, South Africa by silver- or copper-nanoparticle paper filters
T. Dankovich, J. Levine, N. Potgieter, R. Dilingham and J. Smith
Environ. Sci.: Water Res. Technol., 2016, Advance Article
DOI: 10.1039/C5EW00188A

– Interested in more research regarding nano materials and the environment? Please visit our sister blog Environmental Science: Nano. Dr Marina Vance, webwriter in ES: Nano, explains how silver nanoparticles have antimicrobial “super powers”, and also highlights some environmental & health risks and opportunities of nanotechnology in the new Ted X Talk “The Good, the Bad, the Tiny”.

– Water quality is highlighted as one of several “Global Challenges” by the Royal Society of Chemistry. More resources on global, regional and local water quality are available here.

– The same researchers made a small Internet success last year with the viral spread of a project from the Water is Life organization, highlighted by magazines such as Wired, Slate and Smithsonian.

About the webwriter

Jesper Agrelius is a MSc student in Environmental Science at Linköping University, Sweden. His main interests regards environmental science, especially climate change and biogeochemistry. You can follow him on Twitter @JesperAgrelius.

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*Access is free through a registered RSC account.

Humanity faces a grand challenge – sanitation. Worldwide lack of access to basic sanitation is a widely recognized problem for human health, development, the economy and our environment.

Globally 2.4 billion people live without access to improved sanitation and the issue of sanitation lies at the root of many other challenges related to human development, such as education, public health and environmental degradation, and significantly alter economic growth.

Meeting the global sanitation challenge

Faecal Sludge Management (FSM) involves the mechanical or manual emptying of faecal sludge from onsite sanitation systems, and transportation of waste to the treatment facilities using road-based equipment. There are several combinations of transportation technologies and fixed infrastructure that can be used within FSM service delivery.

FSM is often highlighted as an affordable, sustainable and viable technical solution for safe and proper management of faecal sludge, and over the years it has been praised in the literature emphasizing the its potential for meeting the global sanitation challenge. However, there are several limitations related to data, tools and practical examples to support decision makers in the implementation of FSM services.

Ruth Kennedy-Walker and colleagues presented new research recently published in Environmental Science: Water Research & Technology discussing faecal sludge management options for two informal settlements in Lusaka, The Republic of Zambia.

Informal settlements important in sanitation management

Over 60% of the inhabitants in Lusaka live in informal settlements, meaning that sanitation provision via conventional sewerage, onsite septic tanks or formalized FSM services are available only to mid- and high-income residents inhabiting the planned areas of the city. Low income areas have little or no sanitation provision, and large sectors of the city have inadequate infrastructure for meeting the sanitation needs of the population.

Figure 1. Map of Lusaka, capital of The Republic of Zambia. The case study areas, the informal settlements Chazanga and Kanyama, are highlighted with a thick silhouette. The map also shows the existing sewerage network and the community boundaries. Only 9 of the 21 informal settlements in Lusaka are provisioned by the formal sewerage network (Image: Kennedy-Walker et al., 2015).

Evaluating the long-term costs and tools for optimization

This new study addresses some of the issues in sector limitations by presenting a long-term costing methodology for two of the informal settlements in Lusaka. The methodology compares the costs related to a number of feasible fixed infrastructure and transportation scenarios over a 25 year period. The spatio-topological tool developed by the researchers in their analysis was used to model proposed FSM networks – allowing the path of least-time transportation to be identified.

This was used for calculating the net present value and average incremental cost for seven different FSM scenarios over a 25 year design life. The research demonstrated that FSM can be considered an affordable solution for providing sanitation services to the poorest communities of Lusaka. This is valuable information for planners in Lusaka as a decision-support tool, but also very beneficial to the entire sanitation sector.

Clean water and sanitation fundamental for Sustainable Development

Figure 2. The sixth Sustainable Development Goal of total 17: Availability and sustainable management of water and sanitation (Image from UN.org).

Since 2010, the United Nations General Assembly recognized the human right to water and sanitation, acknowledging that sanitation and clean drinking water are crucial to the realization of all human rights (Resolution A/RES/64/292).

Ensuring availability and sustainable management of water and sanitation for all is one of the recently adopted Sustainable Development Goals (SDG). The SDG have certain targets to achieve by 2030, for instance:

• Equitable and universal access to safe and affordable drinking water for all.
• Access to adequate and equitable sanitation and hygiene, with a special attention to the needs of girls, women and those in vulnerable situations.
• Improvement of water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally.

By developing tools that are applicable to the sanitation community in general, the study from Kennedy-Walker and colleagues provides important knowledge and methods for communities and societies that are in need of proper sludge management, especially for those in vulnerable situations such as informal settlements. This can be seen as one of the many steps required to achieve our goal of proper sanitation for all.

Read this exciting research for free* by clicking the link below:

Optimisation and costing of faecal sludge management options for Lusakas’ informal settlements
R. Kennedy-Walker, T. Holderness, D. Aldersson, J. M. Amezaga and C. A. Paterson
Env. Sci: Water res. Technol. 2016, Advance Article.
DOI: 10.1039/C5EW00179J

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About the webwriter

Jesper Agrelius is a MSc student in Environmental Science at Linköping University, Sweden. His main interests regards environmental science, especially climate change and biogeochemistry. You can follow him on Twitter @JesperAgrelius.

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*Access is free through a registered RSC account.

These are the top 10 most downloaded articles published in Environmental Science: Water Research & Technology in 2015. Congratulations to all of the authors whose articles have been featured!

Microbial capacitive desalination for integrated organic matter and salt removal and energy production from unconventional natural gas produced water Casey Forrestal, Zachary Stoll, Pei Xu and Zhiyong Jason Ren Environ. Sci.: Water Res. Technol., 2015,1, 47-55 DOI: 10.1039/C4EW00050A
Bioelectrochemical systems for nitrogen removal and recovery from wastewater M. Rodríguez Arredondo, P. Kuntke, A. W. Jeremiasse, T. H. J. A. Sleutels, C. J. N. Buisman and A. ter Heijne Environ. Sci.: Water Res. Technol., 2015,1, 22-33 DOI: 10.1039/C4EW00066H
Pitfalls and progress: a perspective on achieving sustainable sanitation for all Michael R. Templeton Environ. Sci.: Water Res. Technol., 2015,1, 17-21 DOI: 10.1039/C4EW00087K
Reduction of microbial contamination from drinking water using an iron oxide nanoparticle-impregnated ultrafiltration mixed matrix membrane: preparation, characterization and antimicrobial properties Munmun Mukherjee and Sirshendu De Environ. Sci.: Water Res. Technol., 2015,1, 204-217 DOI: 10.1039/C4EW00094C
Anaerobic membrane bioreactor treatment of domestic wastewater at psychrophilic temperatures ranging from 15 °C to 3 °C A. L. Smith, S. J. Skerlos and L. Raskin Environ. Sci.: Water Res. Technol., 2015,1, 56-64 DOI: 10.1039/C4EW00070F
The water energy food nexus – challenges and emerging solutions John Machell, Kevin Prior, Richard Allan and John M. Andresen Environ. Sci.: Water Res. Technol., 2015,1, 15-16 DOI: 10.1039/C4EW90001D
Detection of trace arsenic in drinking water: challenges and opportunities for microfluidics Nevetha Yogarajah and Scott S. H. Tsai Environ. Sci.: Water Res. Technol., 2015,1, 426-447 DOI: 10.1039/C5EW00099H
Graphene in the Fe3O4 nano-composite switching the negative influence of humic acid coating into an enhancing effect in the removal of arsenic from water Blain Paul, Vyom Parashar and Ajay Mishra Environ. Sci.: Water Res. Technol., 2015,1, 77-83 DOI: 10.1039/C4EW00034J
Selective adsorption of oil–water mixtures using polydimethylsiloxane (PDMS)–graphene sponges Diana N. H. Tran, Shervin Kabiri, Ting Rui Sim and Dusan Losic Environ. Sci.: Water Res. Technol., 2015,1, 298-305 DOI: 10.1039/C5EW00035A
Adsorptive removal of arsenic from groundwater using a novel high flux polyacrylonitrile (PAN)–laterite mixed matrix ultrafiltration membrane Somak Chatterjee and Sirshendu De Environ. Sci.: Water Res. Technol., 2015,1, 227-243 DOI: 10.1039/C4EW00075G