Discussion/Research: Freshwater Issues – ecology & Wildlife

For this post, I intend to look closer at freshwater ecology and wildlife, highlighting various topics and information that acquired from general sources and discussion with my partner, a zoology student from the University of Salford who has studied this subject amongst numerous others throughout the duration of his course.

From this, I was able to gain a useful insight into hydro biology, eutrophication and wastewater in relation to its attributes and effects upon freshwater sources.

As well discussing a brief overview of these aspects involved within fresh sources, Rob also referred to a few lecture sources that felt were relevant in reviewing the physical attributes of water sources, in particular eutrophication which is the result of poor maintenance of healthy water levels. In addition, how such water catchments have been influenced by a variety of agricultural and industrial development.

Again, the sustainability of water supplies in such areas is fairly questionable, even when considering various man-made efforts that seek to emulate the physical conditions of healthy water flow. There is significant evidence to suggest a variety of huge influences upon the diversity of freshwater species as a result.

An example highlighted by Rob was say if a bacteria was introduced into the water as a result of being washed in through pollution, that used oxygen and produced carbon dioxide, even if they needed only small amount and they reached a high mass, which means they would use more oxygen, reducing the overall oxygen concentration in the water, resulting in species that require a higher oxygen levels would likely die out.

Another example of eutrophication is nitrogen from fertilizers being leached from soils e.g. farmland, and running off into streams or ponds. This can stimulate the growth of surface algae which can block all sunlight from reaching the pond, this can decrease the overall oxygen in the water, killing any oxygen dependant life with it.

There is certainly enough of an incentive for human concern in prevention of eutrophication as this process has consequences that negative to human usage, our surrounding environments and the various other life forms within them.

There is also discussion of various measures to prevent this process from occurring, which is likely similar to general practice of freshwater conservationists. It serves to offer a greater degree of understanding in regards to what this process entails and possibly aspects to look out for if I were to visit a conservation day or river clean-up during such stages.

Freshwater microbiology 2013 (1)

•Water Pollution has different effects on lakes and rivers.
•Pollution of lakes and rivers can cause eutrophication.
•Because lake water is not quickly replaced the effects can accumulate gradually, in rivers pollution is eventually washed away to the sea.
•Waste, especially wastewater, from human or animal origin can contain pathogens.

Eutrophication is a natural process that occurs to all lakes over time as the weathering of rocks and soils from the surrounding catchment area leads to an accumulation of nutrients in the water and associated sediments.

Young lakes (and man made reservoirs) usually have low levels of nutrients and correspondingly low levels of biological activity. Such lakes are referred to a being oligotropic from the Greek work oligos meaning little or few. Literally oligotrophic means little-nourished.

Old lakes usually have high levels of nutrients and correspondingly high levels of biological activity. Such lakes are referred to as being eutrophic from the Greek word eu meaning well. Literally eutrophic means well-nourished.

The main causes of eutrophication are:

•natural run-off of nutrients from the soil and the weathering of rocks.
•run-off of inorganic fertiliser (containing nitrates and phosphates).
•run-off of manure from farms (containing nitrates, phosphates and ammonia).
•run-off from erosion (following mining, construction work or poor land use).
•discharge of detergents (containing phosphates).
•discharge of partially treated or untreated sewage (containing nitrates and phosphates).
•In most freshwater lakes the limiting nutrient is phosphorus, so an input of phosphorus in the form of phosphate ions (PO43-) results in an increase in biological activity.

The natural time scale for the aging of a lake from being oligotrophic to eutrophic is of the order of thousands of years. However, a high rate of input of nutrients (from human activities) can increase the rate of aging significantly resulting in eutrophic conditions developing after only a few decades. This artificial eutrophication has already happened in many parts of the world including the Norfolk Broads and parts of Holland, Denmark and Norway.

To renew all the water in a lake may take up to a hundred years compared to a few days for the renewal of the water in a river. Consequently, lakes are particularly susceptible to pollution such as artificial eutrophication.

Effects of Eutrophication

  • An increase in plant and animal biomass
  • •An increase in growth of rooted plants, e.g. reeds
  • •An Increase in turbidity (cloudiness) of water
  • •An increase in rate of sedimentation
  • •The development of anoxic (anaerobic) conditions (low oxygen levels)
  • •A decrease in species diversity
  • •A change in dominant biota (e.g. carp replace trout and blue-green algae replace normal algae) and an increase in the frequency of algal blooms.

Some of the main consequences of eutrophication are:

•increased vegetation may impede water flow and the movement of boats
•the water may become unsuitable for drinking even after treatment
•decrease in the amenity value of the water (e.g. it may become unsuitable for water sports such as sailing)
•disappearance of commercially important species (such as trout)

Reducing Eutrophication

•Treating effluent before it reaches the lake.
•reducing the use of phosphates as builders in detergents.
•reducing the use of nitrate containing fertilisers.
•using tertiary sewage treatment methods to remove phosphate and nitrate before discharge of the effluent into rivers and lakes.
•directing treated waste water away from lakes to rivers and the sea.
•aerating lakes and reservoirs to prevent oxygen depletion particularly during algal blooms.
•removing phosphate-rich plant material from affected lakes.
•removing phosphate-rich sediments by dredging..
The next source discussed the concept of water pollution and its relation to rivers. During this, the classification and causal effects of such pollutants are highlighted and again related by to human action via industrial and agriculture waste and development processes.
Even subtle changes in the biochemistry of the water source can have massive effects upon the conditions that many water based life forms require to survive or breed. Thus, reinforcing the importance of wastewater management and preventing any potential pollutants reaching larger bodies of water.
—Holdgate (1971) defined pollution as something that is present in the wrong place, wrong time and wrong quantity.
—The legal definition of water pollution-Pollution arises by the addition of something to water that changes its natural qualities (Wisdom 1956)
—The introduction by man into the environment of substances or energy, liable to cause hazards to human health, harm to living sources and ecological systems, damage to structure and amenity or interference with the legitimate use of the environment (Holdgate 1979).
What are pollutants?
—Acids and Alkalis
—Anions (e.g sulphides, sulphites, cyanide)
—Domestic sewage and farm manures
—Food processing wastes (including farm processes)
—Gases (chlorine and ammonia)
—Nutrients (phosphates and nitrates)
—Oil and oil dispersants)
—Organic toxic wastes (phenols and formaldehyde)
—Polychlorinated biphenyls
Sources of pollution

Point sources

—Waste water or effluent is discharged into water sources at a particular point.
—e.g. sewage through a pipe
—Most effluents are point sources
Oxygen and Water
—What else can affect the amount of O2 in the water?
—Speed of water flow
—Roughness of surface over which water flows

This final reference refers to waste water, how it is composed and managed and the various significant processes involved within effective sewage treatment. There is wide variety of factors to consider when aiming to repair the significant effects that wastewater pollution can have in surrounding water sources.

For this, there is evidence of various stages of methodology that ensure responsible management, this is likely to be an expensive process which would explain why certain UK water companies have aimed to cut costs when managing wastewater. Restoration near areas of heavy industry are some of the hardest for consistent maintenance, as industrial pollutants both naturally occurring compounds and xeno-biotic compounds (artificially introduced) can only be slowly degraded or reduced, therefore it can prove to be a time consuming process.


The Beginnings of wastewater (sewage) treatment

(But remember water from washing, body and clothes, preparing vegetables, industrial use, rainwater runoff etc.)

Composition of Wastewaters

Wastewater of domestic origin is usually >99% water with up to 1% solids, both suspended and in solution.
Industrial wastewater streams vary greatly depending on the industry.  Abattoirs and food processing plants can produce as much BOD as a small town.
Industrial effluent can also contain toxins.
Preliminary treatment
Removal of dead dogs, foetuses, plastic bottles and other things you cannot pump
Screening through bar screens or perforated plates.
Strainings may be passed through a comminuter (mincer).
Grit Removal – flow slowed to allow grit to settle.
In times of high water flow excess wastewater will pass over weirs and be stored in storm tanks.
Pumping takes energy, sites often sloping to utilise gravity.
Primary Treatment
•Primary settlement = removal of suspended organic matter through sedimentation
•Flow of effluent slowed in circular or rectangular sedimentation tanks
•Settled material = sludge. This is removed periodically together with any surface scum
•Liquid is now termed primary effluent
Secondary Treatment of Primary Effluent

Biological Processes

  • §Activated Sludge
  • §Deep Shaft
  • §Trickling filter (Biological filter)
  • §RBC (Biodisc)
  • §Aerated Lagoons
  • §Integrated Ponds
Land Application of Wastewater
Objective: To utilize the natural soil properties and associated biological conditions to remove undesirable constituents from wastewater.
  • Benefits: Reclamation/Reuse of water and use of nutrients for plant growth.
Areas of Concern:

  • Metals Accumulation
  • Nutrient Uptake
  • Pathogens

Oxidation Ponds

  • Low Cost Treatment Option.
  • Used Primarily in rural areas.
  • Assume these are completely mixed biological reactors without solids return.
  • Mixing provided by heat, wind, and fermentation

Special problems – industrial waste

  • Industry creates either high concentrations of naturally occurring compounds or wholly man-made or xenobiotic compounds.
  • These may be only slowly degraded or may be recalcitrant (difficult or impossible to degrade).
  • All waste must have a discharge consent.
  • Many industries treat waste before disposal

To conclude, I felt that I have refined my knowledge of some the scientific principles involved within freshwater sources and my considered narrative, particularly when considering the conflict of interest between human development via industry & the growing demand upon agriculture due to the mass consumption of an ever increasing population against the desire to reduce water abstraction and consumption and create a sustainable water supply, maintaining healthy water levels and quality to support the natural conditions of healthy freshwater eco-systems and habitats that help reduce the chances of flooding or drought.


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