Environmental Science: Water Research & Technology blog

Beach sand – not just for sunbathers

After hearing the word “beach”, many people automatically think of sunbathing, long walks near the sea, building sand castles and throwing Frisbees – recreation at its finest. Beaches are one of the most visited ecosystems for human recreation and are of high importance for regional economies, in many cases especially for tourism. Beaches and recreational bathing waters are highlighted by the World Health Organization (WHO) as important for health and wellbeing. But did you know that beaches, and in particular the beach sand itself, also plays a vital part in coastal beach water management?

Worldwide public use of water for recreational purposes and recreational activities that involves water have increased over the years. But this also means that recreational exposure to pathogens in the water environment also increases.

Fecal contamination of coastal waters

There are many different kinds of contaminants that humans can be exposed to with regard to water, such as protozoas and trematodas, bacterias and viruses. Current recreational water management practices tend to focus primarily on the beach water itself, excluding the impacts of beach sand on water quality. A wider approach is needed to fully understand how other components of the beach system can influence the water quality.

New research by Qian Zhang, Xia He and Tao Yan, from the University of Hawaii at Manoa, studied what role beach sand has in coastal beach water management.

Beach sand is often highlighted for its negative impact because it functions as a potential source and reservoir to fecal indicator bacteria, often showing higher levels than the surrounding water. This could cause chronic water quality deterioration and hamper proper health risk assessment. However, to get full knowledge of the beach system, we also need to understand the positive impacts that beach sand can have on water quality.

By using microcosms, small experimental and simplified ecosystems, Zhang and colleagues have examined how subtidal beach sand can enhance the decay of fecal bacteria and which underlying mechanisms contribute to the process.

Indigenous microbiota – a significant factor in bacterial decay

The study identified that beach sand indigenous microbiota was the major factor in bacterial decay rates, and showed that higher indigenous microbiota corresponded to faster bacterial decay. This research proved that beach sand actively facilitates the removal of fecal bacteria, which goes beyond the traditional perception of beach sand only serving for contaminant adsorption and retention.

The study shows that beach sand have other functions than just being for recreation, it also contributes significantly to water quality. Thanks to the research findings from Zhang and colleagues, beach water management practices can be improved to include beach sand and other functions of natural processes in beach systems, which would be a more inclusive systems approach. This would also enhance our understanding and management of recreational exposure to pathogens in water.

You can read the full paper for free* using the link below:

Impact of indigenous microbiota of subtidal sand on fecal indicator bacteria decay in beach systems: a microcosm study
Qian Zhang, Xia He and Tao Yan.
Environ. Sci: Water Res. Technol., 2015, 1, 306-315.
DOI: 10.1039/c5ew00004a

—————-

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.

—————-

*Access is free through a registered RSC account.

The purity of water can mean different things to different people. When I call a glass of water pure, am I saying that it’s safe to drink, or clean enough to be labeled as “research-grade”, or do I mean that it has two molecules of hydrogen for every molecule of oxygen and absolutely nothing else? And where can we find the purest, cleanest water in nature?

Image adapted from Wikipedia

It ain’t pure if it’s natural. It ain’t natural if it’s pure. As rain and snow make their way to the earth, they dissolve particles, minerals and gases. Once on the ground as surface water from rain and snowmelt, the water continues to gather dissolved and suspended materials (including microorganisms), as it flows over the soil and the rocks. Rainwater and snow also contain many pollutants and may not be appropriate for drinking without treatment. So, the next time someone tries to sell you a bottle of “pure natural water”, ask where that pure water came from, because, as Machell et al. say in a recent paper, “Pure water does not exist in nature…”.

If it ain’t pure, is it safe? Indeed this is a key question that links drinking water with public health issues. Very few drinking water quality parameters require legal compliance. The Drinking Water Directive in Europe and the Safe Drinking Water Act in the United States are notable exceptions. But most drinking water quality parameters serve merely as guidelines, rather than specific requirements that can be enforced by law.

Due to increasing stresses on our water infrastructure, we are now forced to look for alternative sources of water (such as wastewater reuse, rainwater harvesting and dual distribution systems for potable and non-potable uses).  So, a clear understanding of purity becomes even more important when these alternative sources are used to provide fit-for-purpose or safe-to-drink water.

Image adapted from Wikipedia

“If I find the world’s cleanest, purest water, I can make the world’s tastiest ice.”, said David Rees in an episode of Going Deep (National Geographic).  But he was disappointed after tasting ultrapure water – i.e., water devoid of any impurity. (Perhaps he was also disappointed that he was not allowed do a keg stand, and had to drink the water from a flask.)

In fact, ultrapure water is quite expensive and is an aggressive solvent used semiconductor industry for cleaning wafers – definitely not meant for making the world’s tastiest ice. Rees succinctly summed up the issue: “Don’t overpurify your water – minerals and salts add character.”

An old saying goes: “Water which is too pure has no fish.” Today, we need a more nuanced understanding about water purity to assess the tradeoffs between the cost of treating water and acceptable levels treatment for providing safe drinking water. Indeed, as Machell et al. say, “Water purity is a vague term… Safe water is economical and attainable, whereas pure water is not.”


How does this idea of water purity govern environmental monitoring and risk assessment? Find out by reading the full paper for free* using the link below:

Drinking water purity – a UK perspective
John Machell, Kevin Prior, Richard Allan and John M. Andresen
Environ. Sci.: Water Res. Technol., 2015,1, 268-271
DOI: 10.1039/C5EW90006A, Forum

Maritime transportation is vital for local and global economies and international trade, but it also causes many environmental problems.

Ballast water – safe and efficient, but also harmful

Water has been used as ballast to stabilize ships since the introduction of steel vessels during the last centuries. Ballast water provides stability and manoeuvrability and also compensates for weight changes in cargo loads, fuel and water consumption, among others. Ballast water is crucial for efficient and safe shipping operations, however it also has environmental downsides.

A reason for concern

The transportation of invasive species via ballast water is a serious ecological threat and have received a lot of focus during recent years. There is an International convention for the Control and Management of Ships’ Ballast water and sediment (BWM) that was adopted 2004, which promotes procedures and standards to control and manage the ballast water.

Ballast water management technologies is seen as a key factor in combating ecological and health risks of ballast water. There are several ways to treat ballast water, either mechanical, physical or chemical methods, or in combination. These treatment methods are seen as a response to the ecological threat of invasive species, but the methods themselves also come with certain environmental risks. Chemical treatment of ballast water can result in formation of disinfection by-products, which are thought to have an impact on health.

Formation of disinfection by-products in ballast water treatment
New research by Amisha Shah and colleagues have observed the extent of disinfection by-products (DBP) formation during chemical treatment of ballast water. Chlorine, ozone, peracetic acid (PAA) and chlorine dioxide, predominantly used in ballast water management systems in this order from the former to the later, where used to examine and assess DBP formation in several ballast water types such as seawaters, brackish waters, synthetic- and man-made freshwater. Our knowledge of the potential formation of DBP in saline water is limited and therefore is it important to conduct this type of studies, since many ballast waters often are saline.

Ballast water – hitch-hiking invasive species. Source: http://globallast.imo.org/

Studied DBPs include trihalomethanes (THMs), bromate, and haloacetic acids (HAAs). Approximately 50% of the formation of DBPs occurred within 24 hours of the usual 5 day ballast water treatment holding time. The findings highlight that our understanding of DBP formation in freshwater systems can be partially transferred to saline waters.

The research show several factors that influence DBP formation in saline waters: salinity, dissolved organic matter (DOM) type/concentration, oxidant type/dose and temperature. Particularly salinity seems to influence the bromide concentration and brominated DBPs dominated in high bromide-containing waters. Temperature shows diverse and limited influence on DBP formation: TBAA and CHBr₃ formation was not affected by temperature, whereas DBAA and bromide formation decreased following a disminution in temperature.

Thanks to this study, important factors in DBP formation have been examined so ballast water treatment disinfection strategies can be optimized to limit DBP formation and discharge in our waters – one of many steps towards a sustainable transport system.

—————-

You can read the full paper for free* using the link below:

Formation of disinfection by-products during ballast water treatment with ozone, chlorine, and peracetic acid: influence of water quality parameters
Amisha D. Shah, Zheng-Qian Liu, Elisabeth Salhi, Thomas Höfer, Barbara Werschkund and Urs von Gunten
Environ. Sci.: Water Res. Technol., 2015, Advance Article
DOI: 10.1039/C5EW00061K

—————-

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 @JesperAgrelius.

—————-

*Access is free through a registered RSC account.