Chemical treatment for reuse of waste water effluents in saudi arabia

Reclamation of municipal wastewater is receiving increasing attention in Saudi Arabia. In the reclamation process desalination of wastewater becomes necessary when total dissolved solids (TSS) concentration is high. At most locations in Saudi Arabia the TDS of wastewaters ranges between 2000 and 4000 mg/l. A considerable fraction of the dissolved solids is due to salts of divalent cations, magnesium and calcium. Chemical precipitation of these salts would therefore be required as either a single step treatment in the reclamation process or as a preparatory treatment in conjunction with reverse osmosis or electrodialysis. The present study was conducted to investigate the chemical treatment of raw and biologically treated wastewater at Dhahran. Two chemicals lime and sodium hydroxide were used. Both were effective in reduction of TDS and hardness. Some typical preliminary results of treatment of secondary effluent are given in the following table. {A table is presented}. The low reduction of TDS and hardness when excess lime was used is due to the fact that recarbonation was not carried out. The phosphorus concentration was reduced from 4mg/l to less than 0.01 mg/l at 100 mg/l dose of either chemicals. The secondary effluent before and after treatment contained less than 0.01 mg/l of Cr and Cu and 0.5 mg/l Pb. Zinc Which was present in a concentration of 0.1 mg/l in the secondary effluent Was reduced <0.1 mg/l after chemical treatment. Similar results for inorganic constituents were obtained fro raw wasteWater. The total organic carbon was reduced from 91 mg/l to 38 mg/l and 20 mg/l respectively when CaO and NaOH were used. It is planned to study the effect of various chemical doses in further detail and also include other pollution parameters such as fecal coliforms, total count of bacteria, nitrogen, etc. in future studies.