An example of hydraulic controllability improvement in water treatment plant

Abstract

Water treatment plant "Štrand" consists of 24 filtration fields placed in two filtering plants, "Old" and "New". Filtering plants are supplied with water from two aeration tanks by pressurized pipeline. Present state of filtration fields operation is U-shaped vessel, considering the filtration fields as tanks (in hydraulic sense). Automatic system keeps the water level constant in the field by downstream control. Clogging of filter material increases the water level, and response of control unit is opening of downstream valve as compensation. The valve opening should represent the level of filter clogging. Unfortunately, since all filtration fields are hydraulically connected, the change of water level in one filter will reflect on state of all other filters, preventing the automatic system to function correctly. That was the reason why the system works unstable, and why there is no correct information on filter clogging status. The present paper deals with hydraulic solution of filtration fields separation including design of flume for flow rate measurement. The mathematical model of flow was also presented together with gained experience.

U okviru postrojenja za prečišćavanje vode "Štrand" u Novom Sadu, nalaze se dvadeset i četiri filtarska polja. Raspoređena su u dve filtarske stanice "Staru" i "Novu". Voda se u fitarska polja dovodi gravitaciono, cevovodima pod pritiskom, iz dva bazena za aeraciju. Automatski sistem upravljanja održava konstantan nivo u filtarskom polju pomoću nizvodnog regulacionog zatvarača. Svako povećanje nivoa (usled zapušavanja ispune) automatika kompenzuje otvaranjem zatvarača, čija bi otvorenost trebala ujedno i da pokazuje stepen zaprljanosti ispune. Trenutno stanje je takvo da su sva filtarska polja hidraulički spojena zbog potopljenosti dovodnih cevovoda tako da regulisanje nivoa nizvodnim zatvaračem na jednom filtru, utiče na nivo vode u svim ostalim filtrima. Ova činjenica dovodi do otežanog upravljanja, nestabilnosti u radu postrojenja, a stepen otvorenosti nizvodnog ventila nije direktno povezan sa stanjem ispune na određenom polju. U radu je prikazano hidrauličko rešenje razdvajanja polja sa projektovanjem mernog objekta, jednačine matematičkog modela, rezultati dobijeni na fizičkom modelu preliva, kao i neki problemi na koje se nailazilo u radu.