2. Introduction
2.3. Wastewaters of high organic (biodegradable) matter content
In this thesis, the ecotoxicity of different types of wastewater and their degradation under different conditions were assessed, but, they were of high organic (biodegradable) matter content in common.
Municipal wastewater used came from municipal wastewater treatment plant.Municipal wastewater is consisting mainly of water (99.9%) and relatively small concentrations of inorganic and suspended and dissolved organic solids. Organic matters are carbohydrates, lignin, proteins and their decomposition products, fats, soaps and synthetic detergents, several natural and synthetic organics from the process industries, anddisease-causing pathogens. The inorganic substances may include a number of potentially toxic elements such as arsenic, cadmium, chromium, copper, lead, mercury, zinc, etc. Even if they are not at toxic-level concentrations to humans, they might be at phytotoxic levels, which would limit their agricultural use or at toxic levels to animals or to any other ecosystem compartment.
Apart from municipal wastewater, an industrial and an agricultural wastewater were tested. Agricultural wastewater used came from liquid manure. Ammonia concentration is posing the highest threat to water quality. The running Hungarian National Environmental Program (2003-2008, number 132/2003; X.11. OGy) is emphasizing that the liquid manure produced by agriculture in huge quantities can cause serious environmental risks. Reduction of the environmental impacts of liquid manure can be done by building up disposal ponds with up-to-date technological protection.
Natural formations (compact sand layers or rock) can be considered as technological protection, as well.
29 Animal urine and manure (including polluted straw) are classified into the second waste chapter of EWC (Code: 02 01 06, from harmonized EC rule, under 16/2001.
(VII.18.) KÖM degree). This rule applies to the selectively collected but untreated (in situ) liquid manure as well. In order to prevent and reduce the nitrate pollution in water, the 49/2001. (IV.3.) order controls the professional agricultural activity including the rules of organic manure harmless deposition and disposal. The main goal is to prevent and reduce the nitrate pollution in natural waters, as well as guaranteeing the optimal substrate supply for plants and keeping the soil productivity. Liquid manure can be used as natural fertilizer, under very strict conditions. The nitrogen content of the manure has to be utilized by plants without any nitrogen emission to natural waters.
Our basic aims were to test how the degradation processes, especially biodegradation, affect the toxicity and the organic matter content of different liquid manures. During degradation processes not only concentration of the chemicals (and therefore exposure) will change but also, photo-degradable, hydrolytically unstable, oxidizable and biodegradable substances in addition may form such breakdown products which can be even more toxic than the parent substance was.
Industrial wastewaters were represented by paper mill effluent. Pulp and paper industry is one of the most polluted industries in the world (Thompson et al., 2001;
Sumathi and Hung, 2006). Two main steps are included in the production process:
pulping and bleaching. Pulping is the first step and source of the most pollution of this industry. In which, wood chips (raw material) are treated to remove lignin and improve fibers for papermaking. Bleaching is the last step of the process, which aims to whiten and brighten the pulp. These processes are very energy and water intensive in terms of the fresh water utilization (Pokhrel and Viraraghavan, 2004).
The wastewater generated from this industry include high concentration of chemicals such as, sodium carbonate, sodium hydroxide, bisulfites, sodium sulfide, elemental chlorine or chlorine dioxide, calcium oxide, hydrochloric acid, toxic components, … etc. (Sumathi and Hung, 2006). But, the major problems are the high organic content (20-110 kg COD/air dried ton paper), wood debris, soluble wood materials, adsorbable organic halide (AOX), dark brown coloration, toxic pollutants, etc.
The quality of wastewater generated from pulping and bleaching is significantly
30 distinctive according to the type of process and chemicals (Billings and Dehaas, 1971).
Wood preparation, pulping, pulp washing, screening, washing, bleaching, paper machine and coating operations are the most pollution-generating process stages.
Various studies reported the toxic effect of these by-products in the wastewater and their impacts on the environment. It was reported that pulp and paper industry wastewater has toxic/lethal effect on daphnia, fish, planktons and other biota in the receiving water bodies (Owens et al., 1994; Hickey and Martin, 1995; Yen et al., 1996; Vass et al., 1996;
Liss et al., 1997; Lindstrom-Seppa et al., 1998; Leppanen and Oikari, 1999; Johnsen et al., 1998; Erisction and Larsson, 2000; Schnell et al., 2000; Kovacs et al., 2002).
Dunafin Ltd., Dunacell Ltd. and Dunapack Ltd. are paper, pulp manufacturing and paper based packaging factories in Dunaújváros. Dunaújváros is medium-sized town located approximately 70 kilometres south of Budapest along the bank of the Danube.
Even though, it has large-scale industries (such as the giant Dunaferr steel works, and the Dunapack paper mill), until 2002 the communal sewage collected was discharged without any treatment to the Danube. In 2002 a wastewater treatment plant was opened alongside the Danube. The plant includes mechanical and biological wastewater treatment, as well as sludge treatment by homogenization and thickening. The plant is capable of handling the average and extreme hydraulic and sewage loads. Dunafin and Dunapack Ltd. attach great importance in regulating the technical processes to cause the least possible environmental impact, in accordance with the principles of sustainable development.
They operate an integrated quality control system in order to achieve and maintain this, in accordance with the MSZ EN ISO 9001:2008 and MSZ EN ISO 14001:2004 standards.
The basic aims of this study were to investigate the toxicity of wastewater (treated and untreated) from the pulp-paper industry, emphasize the importance of toxicity tests and the acute toxicity parameters incorporation into the environmental regulations for wastewater discharge to protect the receiving ecosystems, to test how the degradation processes, especially biodegradation, affect the toxicity and the organic matter content of different raw and treated samples, to assess the potential impact on the receiving water body, and to verify the importance of toxicity test in evaluating the wastewater treatment operation and efficiency and its capability in decreasing the hazard of wastewater before discharging it into the environment.
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