Optimization of Hydraulic Contact Time of Treated Wastewater in Firefighting Water Tanks for Reuse (Case study: West-town’s wastewater treatment plant)

Freshwater scarcity is leading the world to research into the reuse and recycling of industrial wastewater.

In this research, in order to improve the quality of the effluent of the treatment plant and the possibility of using it as a source of fire water, the effluent of the wastewater treatment plant of Gharb town was used as an analysis unit. On-site sampling and qualitative tests were performed on samples prepared in 20 liter containers in Tehran University Laboratory. In other words, the method of conducting the present study was laboratory. Data collection tools in this study consisted of pH meter, TDS meter, spectrophotometer DR5000, turbidimeter, and thermal reactor.

This research investigates on Electro-Coagulation and Hydraulic Retention time and the way that it effects on treated wastewater Quality, for so, 9 samples with 20 liters’ plastic pot has been taken and examined in different contact time including 1, 2, 5, 10, 24, 48, 72 hours. The results show that all goals parameters (pH, Total Dissolved Solid (TDS), Phosphate, chloride, Sulfate, total Hardness, Silica, suspended solid (SS), Iron (Fe) and Manganese (Mg) are in standard Range but there is in one sample the Chemical Oxygen Demand (COD) was not in standard Range. Also the experiment shows that all parameters concentration was decreased by time except Hardness and Sulfate which were increase. Also Biologic Parameters examined as well and they were on standard Range.

The results show that the treated wastewater Quality was in Standard Range till 72th hours and after this time due to rapid increasing of Sulfate and increasing of its smell it not suitable for use as water source in firefighting. Further more 9 other samples had been examined after using Electro-coagulation as an advanced treatment and disinfection aid fallowing by Sodium hypochlorite disinfection, the result shows that COD is decreased and all parameters got better for reuse, especially Biological parameters.