Bench scale evaluation of Fe(II) ions on haloacetic acids (HAAs) formation in synthetic water

Abstract

Cast iron pipes were installed broadiy in North American water utilities, particuiariy in dider cities such as Halifax, NS, and other cities in the northeastern portions of Canada and the USA. Many of these cast iron pipes are corroded and are continuous sources of Fe(ll) ions in drinking water distribution systems. In this paper, the results of an experimental investigation into the factors influencing haloacetic acids (HAAs) formation in the presence of Fe(ll) ions are presented. The experiments were conducted using NaHC03 buffered synthetic water sampies with different characteristics (i.e. pH, phosphate, stagnation time) simuiating with water distribution systems. The results showed that Fe(ll) ions significantly reduced HAAs formation in different reaction systems at a 95% confidence level. In control water systems, pH had no significant impact, however, in the presence of Fe(ll) ions in water, pH had an obvious impact to increase HAAs formation (a = 0.05). In contrast, phosphate-based corrosion inhibitor significantly (a = 0.05) reduced HAAs formation in the presence of different dosages of Fe(ll) ions in water samples for the reaction period of 24,48, 84 and 130 h, respectively. Significant factors and their rank Influencing HAAs formation and distribution were identified using a 2" full factorial design approach.

Risk assessment methodology for iron stability under water quality factors based on fuzzy comprehensive evaluation

“…Each evaluation factor had different influence on the evaluation result. Therefore, the membership degree of each evaluation factor corresponding to different evaluation grade was determined by setting membership (8) x j = b j (1 − σ j ), (9)…”

“…Incremental factor and descending factor represented the risk increased with the value of the factor increasing or decreasing. According to the previous researches [7][8][9][10], the increasing concentration of chloride, sulfate and DOM in pipeline water would lead to an increasing risk of iron, while increased pH would led to decrease the risk [11]. The degrees of membership functions are shown in Table 1.…”

“…Sulfate and chloride were the indication of iron shape variation leading to the high concentration of red water [7]. DOM plays a key role in iron stability, could form complicated complexes with iron, meanwhile, the phenomenon of reducing ferric iron colloids to soluble ferrous iron was also recorded [9,10]. And pH was demonstrated to increase the iron stability in actual distribution systems [21].…”

“…Chloride and sulfate were deemed to destroy the stability of iron in the DWDSs, increasing iron concentration in water [7,8]. DOM played a key role in iron stability which was recorded to reduce ferric iron colloids to soluble ferrous iron [9,10]. And the increasing of pH was demonstrated to enhance the iron stability and decrease the iron releasing in actual distribution systems [11].…”

The Behaviour of Haloacetic Acids in Distribution Zones in Scotland

“…Of course these reactions depends on the environmental conditions (pH, temperature, Fe minerals present, bacteria present etc.). Furthermore HAA may be sorbed onto or react within the pipe surface [50,52,57]. Therefore the interior surface of pipes is a crucial factor affecting all of the processes above, but only limited amount of reports are examining the effect of pipe materials on the formation and fate of DBPs and HAAs.…”