Compliance Investigation Of Bevern Stream Environmental Sciences

The Council Directive 91/271/EEC of 21 May 1991 is about the treatment of urban waste waters (domestic waste water or the mixture of domestic waste water with industrial waste). This Council Directive has the aim of regulating pollution of waterways from the adverse effects of urban waste water discharges and industrial discharges. It also involves the collection and treatment of urban waste water. This directive covers a variety of pollutants, the main ones that will be covered in this report are nitrates and phosphates.

The main sources of pollution come from various sources. One of the main source being surface run off after agricultural practices such as fertilisation of farm land with fertilisers and animal waste containing nitrogen and phosphate. Nitrates and phosphates can also be found in domestic sewage waste and industrial waste water.

The pollutants mainly affect the biotic environment such as algae and fish. Humans may be affected through build up of nitrates in drinking water but this is not as sever as the effect of eutrophication on water life. The main effect nitrates and phosphates may have on a river or lake is the process of eutrophication. The tern eutrophiction is defined in Abel, P(2000) as a process by which nutrient levels rise in a lake or river from low levels(oliotrophic) to high levels(eutrophic). A high increase of nitrates and phosphates in a river or lake may bring about an algal bloom. This algal bloom will usually occur at the surface of the river or lake, blocking the suns light and using up oxygen which means plants closer to the river bed will not be able to carry out photosynthesis as effectively which may bring about death. Decomposers will start to brake down the newly formed dead organic mater by the process of decomposition. When decomposition occurs through aerobic respiration they use further oxygen. This will lover the levels of dissolved oxygen within a river or lake. The wildlife within the river will have the same biological oxygen demand but now there will be less dissolved oxygen. This will mean plant and animals less adapt to living in low levels of oxygen will die, which will in turn cause more decomposition.

This investigation is aimed at find out if the Bevern Stream in Sussex is complying with the limits of nitrates and phosphates in the water in accordance with the Council Directive 91/271/EEC and the levels The Sussex Ouse Water Conservation Society have deemed an acceptable value for phosphate concentration and nitrate concentration in the Bevern Stream. The Sussex Ouse Water Conservation Society have set levels of <4mg/l for phosphate and a limit of <5mg/l of nitrogen in the Bevern Stream. If the stream is found to be in breach of the accepted values the local council may be at fault and need to set in place strategies to deal with the problem. The local agricultural community may also have to change their farming practices to limit surface run off of nutrients into the Bevern Stream.

Method

The information gathered has come from the Sussex Ouse Conservation Society which was collected by taking samples of water from various places along the Bevern Stream. The samples that were collected were tested for concentrations of ammonia, phosphate, nitrates and dissolved oxygen. The sites that the samples were taken from were a) Stoneywish Country Park, b) Spathem Lane, c) Swansyard Farm, d) Hamsey Brickworks and e) Clapper's bridge.

The Bevern Stream is one of many tributaries of the Ouse. The Bevern Stream is set on a parent rock of chalk and has a clay soil structure. It has a catchment area of 34.62km2 , which consists manly of rural farm land and also has an oak woodland.

The graphs have been created using excel along with data collected by the Sussex Ouse Conservation Society.

Assessment

The levels of nitrates within the Bevern stream over the past 12 months and for the month of October are all within limits. Sample sites c and d are considerably low showing low levels of nitrates which is good for the local wildlife. There is however high levels of nitrates at sites b and e which at the present levels will not be having an adverse effect on wildlife but may be cause for concern in the future. The local council and farmers may need to start to make changes in this area to stop the problem before it gets worse.

The second graph shows the phosphate concentrations of the Bevern stream. At a glance the graph looks worrying as there are high levels of phosphate. At site a the October limit is 7 mg/l which is 3 mg/l over the accepted value for phosphate concentration, this value is quite high compared to the 12 month average which may suggest that has been a change in land use or a problem with discharge. The opposite has occurred at site b where the October average is a lot lower than the 12 month average which was at a level of 19 mg/l. This value is 15 mg/l over the accepted value of 4mg/l. This is very bad for the environment and may have led to eutrophication of the water. Site c has a high 12 month average but October has saw a decline in phosphate concentrations, this may have been due to some sort of management or new regulation put in place. The best site is site d where the water quality has been within the 4 mg/l limit for the past 12 months and has been continued for October. There has also been an improvement at site e where the October value of 2 mg/l is bellow that of the 12 month average which is 7 mg/l.

Water treatment in the Ouse area for nitrogen has been effective in that all the tested sites have been bellow the set standards. The main issue lies with the phosphate concentration which has been above the set value on a number off occasions.

Conclusion

The quality of water for the Bevern Stream for nitrate concentration does comply with the set standards but the phosphate concentration does not at ever site. This may need to be looked into further and management practices may need to be developed to ensure the quality of the water does not fall any more. This will protect the biodiversity of the stream.

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