Contamination of surface water, precipitation water and groundwater increase thecosts of potable water processing. From the point of view of waterpurification process, water contamination with phosphorus and nitrogencompounds and water eutrophication are the most serious problems.
Withelevated levels of nitrogen pollution, ammonia nitrogen and nitratenitrogen need to be removed from surface and groundwater. As for ammonianitrogen, there are no effective and relatively simple methods of itsremoval from water.
Nitratecompounds can be only eliminated with the use of complicated andrelatively burdensome means.Additionally, nitrate nitrogen is highlysoluble in water and cannot be extracted by coagulation or chemicalprecipitation, which makes it necessary to use expensive methodsinvolving high operating requirements (electrodialysis, reverse osmosis,ion exchange, denitrification). As a result, it is much more difficultto remove excess nitrate ions from tap water than from waste water.
Watereutrophication is primarily caused by increased phosphorus intake,which makes is necessary to purify water by filtering phytoplankton (thelevels of algae and cyanobacteria can be as high as 109 microorganisms/m3 during water bloom). The most difficult to eliminate are cyanobacteria (most notably Microcystis, Aphanizomenon, Anabaena, Nostocales, Oscillatoria, Trichodesmium, Gomphospheria),which ? when in bloom ?have the appearance of blue-green paint orscum, characteristic taste and smell; contaminated water has higherwater turbidity and contains chemically stable toxins dangerous forhuman and animals, able to survive under adverse conditions (toxins arealso released by dinoflagellates, diatoms, or chrysophytes, although to alesser extent).
Cyanobacterialtoxins include neurotoxins (they attack the nervous system),hepatotoxins (they are toxic for the liver and are particularlydangerous for humans), cytotoxins (which are toxic to all types ofcells), dermotoxins (which cause irritation of the skin and the mucosa)and irritants (which cause inflammatory conditions of the skin or therespiratory system). Due to cyanobacterial blooms correlated with thesupply of melt-water and flood water, tap water ceased to be collectedfrom Sulejowski Water Reservoir back in 2004. Contamination withlivestock waste is a problem for the Miedwie Lake, where tap waterintakes for the Szczecin agglomeration are located. The Miedwie Lakecatchment area is heavily exploited by the agriculture (livestockproduction).
Increasein phytoplankton populations is correlated with increased water levelsof organic matter, heavy metals, radionuclides, pesticides, chlorinatedorganic compounds and polycyclic aromatic hydrocarbons adsorbed by algaeand cyanobacteria.
Unconventionalmeans are employed to remove phytoplankton from water (sinceconventional methods proved ineffective), such as coagulation,sedimentation, micromesh filtration and membrane filtration; however,they offer limited effectiveness and do not eliminate algal andcyanobacterial metabolites, and well soluble cyanobacterial toxins.
Apartfrom the costs of potable water treatment, excessive levels ofmicroorganisms in water leads to contamination of water intakes,treatment facilities and distribution installations.Algae blooms canresult in lower performance, clogging and serious failures(microbiological corrosion) of this type of systems, which can be verycostly to repair.
Onthe other hand, large-scale livestock production generates increasedwater demand and consumption. A grower-finisher farm of 80,000 animalsis estimated to consume over 757 m3 of water on a dailybasis. Over 100,000 and 35,000 L of water is consumed to produce 1 kg ofbeef (cattle fed with crop fodder) and 1 kg of poultry meat,respectively. For comparison, to produce 1 kg of potatoes, 1 kg ofwheat, 1 kg of rise, and 1 kg of soya you would need 500 L, 900 L, 1,900L and 2000 L of water, respectively.
Theproblem of increased water consumption is particularly apparent inlarge-scale non-litter swine production where large quantities of slurryare produced. For example, 500 cows and 36,500 grower-finishers produceover 34 m3 and 350 m3 of slurry, respectively, on a daily basis. In practice, there volumes can vary considerably and can reach the level of 800 m3 slurry per day for grower-finishers (Annex X).
Largevolumes of slurry can involve some serious transportation, storage andutilization problems, and significantly increase water consumption.Apart from water given to animals and used for production processes andsanitation activities, additional water volumes are used for slurrydilution which contains more than 8% of dry mass. Depending on weatherconditions, fertilisation period, and plant sensitivity, slurry can bediluted with water at 1:1 - 1:6 proportions. If slurry is diluted withwater at 1:3 proportions at a grower-finisher farm, then waterconsumption will increase by 383,000 m3/year.