2. Pollution Incidents Mark Bennett
Team Leader – Fisheries, Biodiversity & Geomorphology

3. Common Types Agricultural Sewage Algae Oil Slurry Silage Liquor
Most common types of pollution we deal with.
Mostly organic pollutants which can affect water quality even in small quantities.

4. Agriculturall Slurry High Biochemical Oxygen demand Ammonia
Strips Oxygen from water
Ammonia
Toxic
Organic Matter
Nutrient enrichment
Slurry – Liquid/semi liquid faces of livestock mixed with clean or rainwater
Has a manure type odour, brown/dark green colour with high solids
Properties – high biochemical oxygen demand (amount of oxygen needed to break down organic matter). Typically to mg/l. Under Water Framework Directive for a waterbody to meet Good Ecological Status we’d be looking at a BOD of 4 to 5 mg/l.
High Ammonia content, recently measured in a watercourse 35 mg/l. Anything over 1mg/l toxic to fish. To meet good under WFD 0.3 to 0.6 mg/l.
Typical causes of slurry pollution might be spreading on inappropriate fields (land drains) at unsuitable times – frozen/wet ground, just before heavy rainfall. Infrastructure failures, insufficient capacity. Can
Can cause nutrient enrichment.

5. Agricultural Silage High Biochemical Oxygen demand Corrosive
Nutrient Enrichment
Greener colour to slurry, sweeter smell.
BOD of to mg/l.

6. Sewage Effluent High Biochemical Oxygen demand Nutrient Enrichment
- Sewage Fungus
High Ammonia
Visual Impact
Untreated domestic effluent 300 to 400 mg/l.
High ammonia, not as high as slurry
Grey colour, sweet smell (may have noticed as you drive past sewage works if wind is in the right direction)
Sewage fungus – present if ongoing for more than a few days – grey, slimy furry growth on bed or surfaces.
Can be confused with Phaeocyctis – naturally occulting algae, particularly early spring. Brown, foamy – May Rot on beaches.

7. Algae Naturally Occurring Blooms Diurnal changes in dissolved oxygen
Sudden crash impacts dissolved oxygen
Can be toxic
Naturally present.
In suitable conditions can experience blooms. Nutrient enrichment, sudden increase in temperature, light, lack of other plants/shade.
Can cause diurnal changes in dissolved oxygen. Water becomes supersaturated with oxygen in day and drops over night, lowest first thing in morning.
Sometimes crashes occur and oxygen levels drop very suddenly as dies off. Can be caused by sudden changes in temperature, heavy rainfall.
Blue Green algae – can be toxic. Harmful to wildlife, domestic pets. Can cause rashes and illness in humans if ingested. Local Environmental Health are the lead on these incidents with our input on Identifying if blue green .

8. Oil
Covers water course
Toxic to fish
Reduces oxygen exchange