How Statistics and Engineering Form an Integral Part of the Solution


  • Author: Lillian Pierson P.E.
  • Date: 07 Jun 2016
  • Copyright: Image appears courtesy of Getty Images

The story about eutrophication of the coastal waters in the North Sea is nothing new; Scientists have been clamoring about it for decades now. Eutrophication, you know? The process by which an aquatic ecosystem is over-enriched with organic nutrients like nitrates and phosphates. Oftentimes, eutrophication causes severe algal blooms, which then deplete oxygen levels and consequently kill fish populations (also known as a “fish kill”). As bad as it sounds, eutrophication is somewhat normal these days. What is new, however, are the recent and ongoing ecological damages incurred by the North Sea’s coastal ecosystem, due in part to poorly performing environmental engineered processes. This article describes some of the ill effects that have recently been observed in the North Sea, and then goes on to describe how statistics and engineering play an integral part of the solution to problems like this.

thumbnail image: How Statistics and Engineering Form an Integral Part of the Solution

Over the last 30 years, a litany of environmental regulations were passed in an attempt to reduce eutrophication in the North Sea by decreasing the nutrient load of surface waters flowing into it. This is a logical approach that has been used the world-over. From the Florida Everglades to Quebec, Canada, environmental scientists and engineers have been successfully restoring ecological balance by reducing the nutrient load of waters flowing into ecological systems. But in the case of the North Sea coastal zone, something has gone very wrong with recent remedial efforts and only Phosphorous levels have decreased, while Nitrogen levels remain largely unaffected.

On first consideration, a layman may think to himself, “Well, besides the Nitrogen levels, less Phosphorous is still a good thing. At least half the battle is won!” Sadly, though, this is not how things generally work when it comes to aquatic ecosystem contamination, as researchers from the University of Amsterdam and the Royal Netherlands Institute for Sea Research have recently evidenced. In a recent investigation led by Dr. Jef Huisman, researchers discovered North Sea waters measuring a Nitrogen:Phosphorus ratio of 375:1, where normal seawater concentrations of Nitrogen-to-Phosphorous should be about 20:1.

Environmental engineers and scientists commonly use multivariate statistics... to better understand the fate and transport processes of organic nutrients like Nitrogen and Phosphorous.

How this Nutrient Imbalance is Disturbing Aquatic Life in the North Sea

This nutrient imbalance means that the North Sea is Phosphorous-deficient. Consequently, some species of micro-organisms are barely able to subsist, while others are carrying on quite well. For example, researchers found that the growth of foam-producing algae is limited by the current Phosphorous-deficient environment, but that the Dinoflagellate populations that often responsible for toxic blooms are actually better off due to this ongoing nutrient imbalance. Even more concerning still, the algal populations that are managing to get-by are functioning as a nutrient-poor food source for the shell fish and zooplankton populations that feed off of them. Left unchecked, this nutrient imbalance has the potential to decrease the overall carrying capacity of the North Sea’s coastal zone, and the functioning of its ecosystems.

How Statistics and Engineering Form an Integral Part of the Solution

Environmental engineers and scientists commonly use multivariate statistics in order to decrease the complexity of large environmental datasets, and to better understand the fate and transport processes of organic nutrients like Nitrogen and Phosphorous. More specifically, geochemical researchers deploy the following multivariate statistical methods:

• Cluster analysis – In surface water evaluations, cluster analysis is often used to group and characterize contaminants that have similar fates.
• Principal component analysis – Principal component analysis is often used to simplify complex relationships between water quality parameters, in order to uncover what principal components are responsible for deleterious environmental outcomes.
• Factor analysis – Factor analysis is useful for analyzing surface waters in order to uncover significant correlations between water quality parameters.
• Discriminant analysis – In surface water evaluations, discriminant analysis is used to discover information about the similarities and differences between sampling sites and times, and to discover which water quality variables are responsible for location-based and time-based differences in water quality.

Once researchers understand the nutrients’ fate and transport processes, they’ll be able to identify and quantify the sources of these organic nutrients, as well as their likely destinations. Engineers can then begin evaluating different technologies for removing the organic nutrients. Rural and agricultural properties are the biggest culprits when it comes to releasing Nitrogen and Phosphorous into the environment. For removal of these organic nutrients, some proven wastewater treatment technologies include:

• Septic tanks
• Sand filters
• Package wastewater treatment plants
• Constructed wetlands

More specifically, for Nitrogen removal, biological technologies like activated sludge treatment and trickling filtration are particularly useful. If you’re interested in reading more about the problems in the North Sea or the corrective measures discussed here, you can find more information within the source documents listed below.


1) Environmental policy behind imbalance in phosphorus, nitrogen levels of the North Sea. Science Daily. 18 January, 2016.
2) Good Practice Guide Series. KIMO. February, 2011
3) Nitrogen Reducing Technologies for Onsite Wastewater Treatment Systems. Washington State Department of Health, June, 2005.
4) Nitrogen Removal in a Full-Scale Domestic Wastewater Treatment Plant with Activated Sludge and Trickling Filter. Journal of Environmental and Public Health. 27 February, 2013.
5) Statistical analysis to characterize transport of nutrients in groundwater near an abandoned feedlot. Hydrology and Earth System Sciences. 22 October, 2013.

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Published features on are checked for statistical accuracy by a panel from the European Network for Business and Industrial Statistics (ENBIS)   to whom Wiley and express their gratitude. This panel are: Ron Kenett, David Steinberg, Shirley Coleman, Irena Ograjenšek, Fabrizio Ruggeri, Rainer Göb, Philippe Castagliola, Xavier Tort-Martorell, Bart De Ketelaere, Antonio Pievatolo, Martina Vandebroek, Lance Mitchell, Gilbert Saporta, Helmut Waldl and Stelios Psarakis.