Sunday, June 12, 2011

An Introduction to Wastewater Treatment

Wastewater treatment technologies and their developments are significant in the lives of all people. This is true whether they are conscious of the intricate system under the earth or not. Vancouver, with its population of 2 million, produces around 1 billion liters of wastewater every single day. In cities throughout the world, wastewater must be transported and treated with care in order to contribute to creating a high standard of living for its people.

When wastewater from a city reaches a wastewater treatment plant, it goes through a pretreatment process. Here a 6mm mesh is run through the water to catch plastics or stones or any inorganic matter, which could disrupt the wastewater treatment system. After pre-treatment there are three levels of cleaning technologies available for the water; primary, secondary and tertiary.

Afterwards, the wastewater is transferred into a sedimentation tank. This step of primary treatment is primarily a physical process, where the water is allowed to settle into its different components. The oils and greases rise to float on the water, and the biological waste drops to the bottom to form sludge. This treatment stage can remove approximately 60% of TSS (Total Suspended Solids) from the wastewater. The layers are separated and the solid waste is brought to landfills treated and dried in lagoons to later be used as biosolids. In Vanoucer 2 of its 5 major treatment plants, Iona and Lions Gate plants, still only treat the water with primary treatment.

Secondary treatment can be found in the Northwest Langely, Lulu Island and Annacis island plants. The secondary treatment processes can remove up to 90 percent of the organic matter in wastewater by using biological treatment processes. Generally, anaerobic bacteria is added to the wastewater to break down sugars, fats, and short chain carbon molecules. There are many different types of secondary wastewater treatment technologies available.

The third level or stage of treatment is tertiary treatment. Few cities in the world have achieved the successful implementation of this technology. The controversy in tertiary treatment is its very high costs as well as the end product. The water is clean enough to be returned into the taps of the city. Generally populations are uncomfortable with the use of this type of water. Tertiary treatment generally includes various types of disinfection and microfiltration. It is often called ‘water polishing’ or ‘effluent polishing’.

Recently the Canadian Council of Ministers of Environment announced that all wastewater treatment facilities in the country must be at least secondary treatment plants. In the next 20 years Metro Vancouver plans to upgrade Iona and Lions Gate to fulfill these regulations, as well as fulfill the city’s own sustainability goals.

Click here for a nice explanation of wastewater treatment with visuals:

Thursday, June 9, 2011

Forest harvesting impacts on peak flows

As a Hydrotechnical Engineering (one of the areas of specialization in Civil Engineering) student, my area of focus is reservoir operation during high flow events. Although I just use the inflow data other specialists provide me with, hydrology and inflow forecast is the starting point of reservoir operation planning process. Forest harvesting as an influential element which can change the inflow amount until forest regrowth is complete, has been a controversial area of study in forest hydrology.

In the eyes of the public and usually policy-makers, logging trees and removing forests increases the magnitude of floods and consequently exacerbates its destructive impacts. On the other hand, historically, forest hydrologists have tended to rely on the chronological pairing analysis of peak flow events to study the impact of forest harvesting on peak flows which has led them to have opposite views ("Forest impact on floods due to extreme rainfall and snowmelt in four Latin American environments 1: Field data analysis" as one of the most recent examples). Throughout the years, many scientists have demanded that the public and policymakers improve their understanding of natural phenomena such as floods. But is it the public who need to improve their understanding of the behavior of nature?

In order to study the impacts of forest harvesting on peak flows, there are usually two small neighboring watersheds (which are quite similar) that are chosen, one as control watershed which remains unchanged and the other one as treatment watershed which is clear-cut, or treated in another way depending on the objectives of the study. Using statistical methods, the relationship between paired peak flows, which stem from the same meteorological events in the neighboring watersheds, is captured and used to figure out how this relationship changes as the result of clear-cutting in the treatment watershed. This type of pairing of the events is known as chronological pairing. To avoid getting too technical or going through statistical complexities involved in making inferences from the graph results of this type of pairing, let us suffice to say that the related studies tend to conclude that the impact of forest harvesting on the magnitude of peak flows diminishes as the size of the meteorological event increases so that the highest peak flows are almost unchanged. Moreover, in some cases there are suggestions that peak flows with the return period of higher than a particular number of years, like 10, are not affected by logging.

Recently, Younes Alila, a professor at the Department of Forestry in University of British Columbia, and his colleagues have published a paper on the topic utilizing frequency-based pairing of events. In the paper, the authors reveal how chronological pairing of events leads to an irrelevant hypothesis and how the blind use of some statistical methods to support the hypothesis without giving sufficient thought to the process has misled forest hydrologists for several decades. The authors, through appropriate and insightful use of statistical methods accompanied with physical reasoning of natural phenomena, finally prove that the public view on the impact of forest harvesting on floods turns out to be closer to reality than traditional view in the forest hydrology studies.

The publication of the paper as a new paradigm to dismiss years of controversy over the impact of forest harvesting on flood magnitude, at least for small watersheds, has been objected by some scientists who have spent several years of their career on similar studies with opposite conclusions. For further reading, below you can find the links to the original paper, a critique to the paper, and the reply of the authors to the critique.

Forests and floods: A new paradigm sheds light on age-old controversies.

Comment on “Forest and floods: A new paradigm sheds light on age-old controversies” by Younes Alila et al.

Reply to comment by Jack Lewis et al. on “Forests and floods: A new paradigm sheds light on age-old controversies”

Wednesday, June 8, 2011

Happy World Oceans Day!

I hope everyone is out celebrating at or near the ocean today if they can. If you managed to organize or attend a water party, good for you!

Check out Steve Johansen's call to celebrate World Oceans Day every day!

To find out about some of the issues and celebrations happening around the globe today, check out....

Thursday, June 2, 2011

Amazing song about Tahltan First Nations Sacred Headwaters Campaign

Rachelle Van Zanten - My Country (Official Video) from Taylor F. on Vimeo.

Rachelle van Zanten is a fantastic Canadian singer/songwriter who recently wrote a song for the Tahltan First Nation's campaign to protect the Sacred Headwaters of the Nass, Skeena and Stikine Rivers in BC. Check out this emotional and fantastic music video by Taylor F.

Through some geographic serendipity, these three rivers are all born in the same watershed, a place of wild beauty and untouched terrain. The watershed is also home to Caribou, Wild Salmon, and many other less famous but equally important species.

So it is concerning, to say the least, that Royal Dutch Shell is planning to drill over 1000 Coalbed methane wells into the this watershed, potentially causing damaging effects to this ecosystem stretching from the headwaters to the Pacific ocean. The potential ecosystem-level damage of this project has had little voice. Recently, though, it got one. The female elders of the Tahltan First Nation conducted a peaceful protest to stop initial drilling of Klappan Mountain by Fortune Minerals, and most of the elders were arrested. The second voice, was Rachelle.

Click here for more information on the campaign, and check out this teaser for a great film called Awakening the Skeena.

What better way to celebrate world oceans day than to listen to music about water and protecting our sacred province!