Hidrológiai Közlöny 2006 (86. évfolyam)

3. szám - Kaposvári Kázmér: Effect of the intervening ozonizing and Biologie Activated Carbon treatmant to drinking water produced by water supply intake at the River Tisza Szolnok

23 Effect of the intervening ozonizing and Biologic Activated Carbon treatment to drinking-water produced by water supply intake at the River Tisza Szolnok Kaposvári, Kázmér Water and Sewage Works Franchising Joint Stock Company, 1 Vizmü Str., 5000. Szolnok, Hungary. Abstract: The 45000 m

3/d nominal capacity Szolnok Surface Water Plant is constructed on the Hungarian section of Tisza river which is supplying potable water for 112000 consumers. Earlier there were complaints against the quality of the water in respect of taste-odor, toxic organic micro contaminants and biological stability. In 1998, within a water quality improvement program, a 6 kg/h interfacial ozonization process - open GAC adsorber with 16 minutes retention time and 2,5 kg/h capacity chlorine-oxide post-sterilizer - was installed. At the activated carbon adsorbers, the stabilized BAC operation was reached in approximately 3 months. As in may other applications the flocculation (clearing) —• ozonization —• quick sand filtering —> GAC/BAC adsorption —> post-sterilization process proved to be operable here too and solved the water quality problems which the Szolnok Surface Water Plant was earlier facing with. If required, the process can be further improved by applying advanced oxidation processes and nano-filtering. water quality, oxidative stabilization, Tisza River. Keywords: 1. Introduction: The inhabitants of Szolnok city and seven surrounding settlements are supplied with potable water from the Szolnok Surface Water Plant. The number of consumers is 112 thousand people. The length of the distribution network is 620 km. There are chemical and foodstuff plants, as well as highly populous medical and other public institutions operating on the concerned area. The nominal capacity of the water plant is 45.000 m

3/d. The available geologically protected water reserve is less than 5 l/person/day in the area. The Tisza river and the above-ground water treatment has exclusive importance in the potable water supply to the region. This role implies the chances of water quality problems and the consumers' demand for enhanced water purification. Besides the regular industrial, agricultural and municipal emissions, the frequency of emergency situations is also high in the catchment area of Tisza river. The water quality problems started from the mid 1950's. The consumers' complaints were initiated primarily by the taste and odor deficiencies. The presence of the toxic, organic micro contaminants, responsible for a medical risk to the consumers was proved by the extensive water quality tests. The biological examinations permanently showed the increased number of algae and Zooplanktons, as well as the other seasonal biological species. The GC-MS measurements in the raw and the purified water showed the existence of PAH and WHO blacklisted materials (having molecular biological importance) among the identified other 342 organic micro components. The water quality concerns were mainly caused by process related problems. The upgrading of the purification plant

1 - which was built in the 1910's and was redesigned several times - has not followed the increasing contamination of the Tisza river from the 1950's. The process missed the effective chemical treatment stages. The mechanical and partial chemical cleaning was not enough to achieve the ' The first water purification plant was built in 1910 having a 2400 m

3/day capacity. The treatment (purification) of the water from the Tisza river was provided by a state of the art technology, the best of that time. After passing an aluminium salt cleaning and settling stage, the produced water went to a slow filter, then to a chlorine-lime poststerilization unit and finally reached a 300 m

3 capacity storage. The water treatment plant was supported by a 28,5 km long distribution network and 600 m

3 capacity overhead storage. The first water purification plant was modified several times and it remained in operation till 1979. sufficient stability of the water quality and the distribution network. (

Nagy G. - Hegedűs //., 1987) In 1989 we worked out a water quality enhancement conception at the Surface Water Plant. This concept had the primary target of developing the facilities for the high efficiency chemical treatment. The design and construction was preceded by a one and a half year long small scale model experiment (Q=l,5 m

3/h) (Palicska J., 1989). The new, enhanced efficiency process is in operation since 1998. The present paper gives a presentation about the operational experiences of the interfacial ozonization —> quick sand filtering —» activated carbon adsorption —> post-sterilization process installed at the Szolnok Surface Water Plant, and about the outstanding improvement in the potable water quality. 2. The potable water quality complaints and the main reasons for them before the renewal of the treatment process. 2.1. Typical parameters of the potable water quality It is obvious that for the exact and objective evaluation of a water quality, the results of the standardized water quality tests should be taken into account. However, the sensing complaints of the consumers on the taste, odor and the color should not be ignored either, especially in those cases when the deficiencies are creating sensations other than the naturally familiar ones. (

Ollős G., 2000) Odor and taste detection of the raw water is a daily activity. The taste and odor deficiencies were creating problems for almost two decades. In 30% of the odor detection tests and in 25% of the taste tests the anomaly could be sensed in 4-5 fold dilution of the water. According to the tests carried out by the ANTSZ (central medical and sanitary supervisory authority), besides the biological originated agents (geosmin 2-MIB etc.) the taste and odor changes were probably caused by materials unequivocally resulting from external sources (phenols, cresols and oil derivatives). The test also drew the attention to presence of primary aromatic amines (naftil amin, tolidin). According to the former Hungarian water qualification standards, the MSZ 450/1 and the MSZ 450/3, several regular components are also nominated as the generators of frequent complaints (see Table 1). The increase of the ammonia level is the function of the Tisza water cooling. From the mid of November till the end of January the measured values were high - sometimes reaching 1,5 - 2,5 mg/1 - in the potable water. In the rest of the year the concentration of the ammonia-ions is below 0,2 mg/l. Research results support the theory (Golterman H. L., 1962) stating that the ammonia build-up in wintertime can