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

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.

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 30 000 to 40 000 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.

Agricultural Silage High Biochemical Oxygen demand Corrosive Nutrient Enrichment Greener colour to slurry, sweeter smell. BOD of 40 000 to 80 000 mg/l.

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.

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 .

Oil Covers water course Toxic to fish Reduces oxygen exchange