Effect of Remineralization on Ozonation and Biodegradation of Surface Water R. Desjardins, C. J. Zoungrana, M. Provost. Polytechnic of Montreal, Canada. Surface water with low mineralization is often high in natural organic matter. These characteristics make treatments designed to produce drinking water difficult. In order to improve the treatment, some water distributors have introduced a remineralization stage in the treatment line that consist in increasing alkalinity and the hardness of the water by adding calcium ions and bicarbonates ions. The position of the remineralization in the line varies, depending upon the desired objective (buffer effect at the coagulation stage, correction of aggressivity, direct oxidation by ozone, etc.). Tests were carried out in order to show the effects of remineralization on the evaluation of biodegradability of natural organic matter and on some disinfection of by-products during ozonation and biodegradation. These treatment steps are preceded by coagulation- flocculation-decantation and sand-anthracite filtration. Results have shown that remineralization increase the reduction of UV absorbance by ozonation. Remineralization also increases the production of oxalate and biodegradable dissolved organic carbon (BDOC). Results have also shown that remineralization increase removal of chlorine demand, chloropicrine and haloacetic acids by biological treatment (ozonation and biodegradation). Source: 2nd International Symposium on Ozone Applications Havana, Cuba - Mach 24-26, 1997.