Putting the ‘waste’ in ‘wastewater’

Wastewater Constituents

Life today is busy. We don’t have time to be concerned about primary needs anymore. Water, food and shelter are services we pay for. Outsourcing these has allowed us to move beyond our base requirements and seek out other interests. But at what cost? OK, there’s financial costs like rent and rates. But aside from that the cost is a disconnect. When we turn our tap on or get into a shower do we think about where the water comes from? Where is our food from? What about the materials to make the building you live in? Not many people care and yet they have some idea of an answer. Food from farms, water from dams, wood from forest etc. Not wrong, but not really the full picture. As long as water comes out of the tap and there’s food on the selves who cares?  But here’s one that you may not have an answer to.

Where does our waste go?

Not just what you flush, but what goes down every drain. Blackwater, greywater, industral waste etc. etc. it has to end up somewhere. So who cares about that? Probably not anyone with reliable waste services. But should we care? Blissful ignorance is at the root of why many of today’s biggest issues are still problems. And wastewater is one of those topic people are very happy being ignorant of.

Turns out we probably should care. Many components of wastewater are potentially harmful to not only the environment but ourselves. While books can and have been written on various constituents (that’s the things in wastewater that aren’t water) I’d like to draw focus to one particular group.

Heavy metals

Heavy metals are a group of metals that are characteristically dense, all of which are toxic when found in above threshold levels. The exposure of marine organisms to toxic levels of metal contaminants can cause damage to tissue, inability to regenerate damaged tissue, growth inhibition, damage to DNA and more. Toxic concentrations of these contaminants are present mostly in higher trophic feeders (top of the food chain) thanks to a process called bio accumulation. Once introduced into primary food sources, contaminants can work their way up a food chain, amplifying dramatically through each trophic level.

Certain types of algae and bacteria are great at assimilating heavy metals. In fact some are more effective than methods used today to filter out heavy metals. These algae are eaten by the next higher order organism and so on up until top order predators. As these metals are not metabolized and marine organisms have poor coping mechanisms they stay in the food chain until reaching the top order predator or becoming sediment once the organisms dies. The increasing severity of heavy metal contaminates is being well documented by journalists and researchers.

A recent Harvard study suggests that mercury occurrence will rise by around 50% in the next several decades.

Numerous recent studies have detected dangerous levels of heavy metals in large fish stocks, including tuna and salmon. While these fish are touted as a healthy alternative they may harbor hidden dangers in the form of these bio accumulated heavy metals. As a result people are being urged to avoid certain fish stocks around areas such as the gulf of mexico, or to eat only in moderation. As an example, tilefish in the gulf of mexico was found to commonly contain 3 times the toxic threshold for human consumption.

Where do heavy metals come from?

Obviously heavy metal contaminants are a big issue. A recent Harvard study suggests that mercury occurrence will rise by around 50% in the next several decades. So where do these contaminations come from? There are background amounts of heavy metals in marine ecosystems from general erosion. Higher concentrations however, are found around populated areas, in particular industrial areas. However, exactly how much heavy metal humans contribute to systems and its direct effect is still poorly understood.

It is widely agreed that most sources of heavy metals originate from industries such as printed board manufacturing, metal finishing and plating, semiconductor manufacturing, textile dyes as well as civil inputs like street runoff and Landfill leaching.

What can we do about it?

Aside from eliminating the deposits at the source the solution is to mitigate environmental flows containing heavy metals. Therefor it is necessary to treat metal-contaminated wastewater prior to its discharge to the environment.
In most western countries the discharge of heavy metals in industrial waste is tightly regulated. But in developing countries pollution restrictions are poorly enforced or completely absent. While maintaining and improving methods of heavy metal isolation in developed countries is important, the next challenge is ensuring development in this area is made in industrial areas where restriction of wastewater discharge is not enforced.

Heavy metal removal from inorganic effluent can be achieved by conventional treatment processes such as chemical precipitation, ion exchange, and electro-chemical removal. These processes work effectively however they have some significant disadvantages, such as incomplete removal, high-energy requirements and production of toxic sludge. New innovative ways of separating heavy metals from wastewater are currently being investigated. One such product is a coffee infused foam that separates lead.

Check out the blog below to find out more about heavy metals in wastewater!

Any thoughts? Comment and let me know.

No thoughts? What is your favourite heavy metal song?