Yi-Pin Lin

Evaluation of Lead Release in a Simulated Lead-Free Premise Plumbing System Using a Sequential Sampling Approach.

In this pilot study, a modified sampling protocol was evaluated for the detection of lead contamination and locating the source of lead release in a simulated premise plumbing system with one-, three- and seven-day stagnation for a total period of 475 days. Copper pipes, stainless steel taps and brass fittings were used to assemble the “lead-free” system. Sequential sampling using 100 mL was used to detect lead contamination while that using 50 mL was used to locate the lead source. Elevated lead levels, far exceeding the World Health Organization (WHO) guideline value of 10 µg·L−1, persisted for as long as five months in the system. “Lead-free” brass fittings were identified as the source of lead contamination. Physical disturbances, such as renovation works, could cause short-term spikes in lead release. Orthophosphate was able to suppress total lead levels below 10 µg·L−1, but caused “blue water” problems. When orthophosphate addition was ceased, total lead levels began to spike within one week, implying that a continuous supply of orthophosphate was required to control total lead levels. Occasional total lead spikes were observed in one-day stagnation samples throughout the course of the experiments.

Effects of pH value, chloride and sulfate concentrations on galvanic corrosion between lead and copper in drinking water

Environmental context Galvanic corrosion has been recently reported as the main cause of lead contamination in drinking water in urban cities. Conditions that can deter or promote galvanic corrosion, however, are not well understood. Fundamental investigations exploring the mechanisms and processes involved in galvanic corrosion in drinking water could help to implement proper corrective measures to safeguard public health from lead contamination. Abstract This study investigates the effects of pH value, chloride and sulfate concentrations on galvanic corrosion between lead and copper in drinking water. We hypothesised that galvanic corrosion would occur immediately when a lead–copper couple is first formed and that the release of lead would be suppressed by the subsequent formation of lead corrosion products. Therefore, unlike previous long-term studies using harvested lead pipes, batch experiments employing high-purity lead and copper (99.9%) wires under stagnant and completely mixed conditions were conducted for a 7-day period to test our hypotheses. It was found that enhanced lead release was indeed observed after the lead–copper couple was formed and the lead profiles after 48h were strongly influenced by lead corrosion products formed in the system. Under stagnant conditions, reducing pH and increasing either chloride or sulfate concentrations promoted lead release, leading to the formation of lead corrosion products such as cerussite and hydrocerussite as experiments proceeded. The effect of chloride concentration on total lead concentration measured in the aqueous phase was similar to that of sulfate at the same molar concentration, showing that the chloride-to-sulfate mass ratio may not provide a good indication for total lead concentration in water. This study provides essential information on fundamental mechanisms and processes involved in galvanic corrosion in drinking water and may be used to explain related phenomena observed in real drinking-water distribution systems.

Effects of pH value and temperature on the initiation, promotion, inhibition and direct reaction rate constants of natural organic matter in ozonation

The effects of pH value and temperature on the initiation (kI), promotion (kP), inhibition (kS) and direct ozone reaction (kD) rate constants of natural organic matter (NOM) in water ozonation were investigated in this study. These rate constants were determined using a newly developed method that integrates the classical Rct concept, the transient steady-state hydroxyl radical (˙OH) concentration model and the pseudo first-order ozone decomposition model. Suwannee River fulvic acid (SRFA) was selected as the model NOM. Our results showed that (1) the variation of pH value from 6.5–8.0 had little influence on kP; while kI showed a peak value at pH 7.5, and kS and kD increased with increasing pH, (2) at room temperature, the value of kD is 2.7–5.8 times higher than kI and that of kP is 14–31 times higher than kS at pH 6.5–8.0, indicating that direct ozone reaction and promotion reaction are the dominant pathways for SRFA to react with ozone and ˙OH, respectively, and (3) all rate constants showed a strong dependency on temperature and the activation energies for initiation, promotion, inhibition and direct ozone reaction were determined to be 55.3, 25.6, 50.1 and 49.1 kJ mol−1, respectively. Functional groups in NOM that are potentially responsible for these reactions were discussed. Our results provide deeper insight into the reactions between NOM and ozone/˙OH, and the removal of micropollutants in the ozonation process can be evaluated using the rate constants determined in this study.

Effects of dissolved oxygen, pH, salinity and humic acid on the release of metal ions from PbS, CuS and ZnS during a simulated storm event

Metal sulfides serve as the sinks of toxic heavy metals in anoxic sediments. Once exposed to fluctuations in environmental conditions, dissolution of metal sulfides can occur and release toxic heavy metal ions into water column. In this study, we investigated the effects of dissolved oxygen (DO), pH, salinity and humic acid (HA) on the dissolution of CuS, PbS and ZnS using batch experiments with continuous aeration to simulate the re-suspension of these metal sulfides during a storm event. Experimental results indicated that oxidative dissolution of CuS, PbS and ZnS occurred in the presence of DO. The rate was the fastest for PbS, followed by CuS and ZnS. Soluble metal concentrations also increased with decreasing pH under oxic conditions. Compared to metal sulfides dissolution rates in freshwater without HA, the presence of saline conditions and HA generally accelerated the dissolution of CuS but inhibited the dissolution of PbS and ZnS. A higher saline or HA concentration, however, did not always lead to a stronger enhanced or inhibited dissolution rate, which could be a collective effect resulting from ligand-enhanced dissolution, complexation, and decreased oxygen and proton attacks due to HA adsorption on the metal sulfide surfaces.

A new scenario of lead contamination in potable water distribution systems: Galvanic corrosion between lead and stainless steel

Lead pipe has been banned for distributing drinking water in the 1980s and partial replacement of lead pipes with stainless steel pipes has been practiced in many Asian countries. Due to the different potentials of lead and stainless steel, galvanic corrosion may take place. The extent of lead release and effects of water chemistry on this process, however, are largely unknown. The objectives of this study are to characterize lead release resulting from galvanic connection between lead and stainless steel, the effects of pH, chloride and sulfate concentrations on this process, and the effectiveness of using orthophosphate to mitigate this problem. The experiments were conducted by connecting aged lead pipes to stainless steel fittings and placing the couple in different water conditions. The results of this study demonstrated that lead release significantly accelerated when lead and stainless steel were galvanically connected and the rate of lead release accelerated with decreasing pH and increasing chloride-to-sulfate mass ratio (CSMR). Orthophosphate could effectively reduce lead release but CSMR needs to be considered since water with a higher CSMR still caused more lead release when galvanic corrosion took place.

Lead as a legendary pollutant with emerging concern: Survey of lead in tap water in an old campus building using four sampling methods

In this study, a sampling campaign with a total of nine sampling events investigating lead in drinking water was conducted at 7 sampling locations in an old building with lead pipes in service in part of the building on the National Taiwan University campus. This study aims to assess the effectiveness of four different sampling methods, namely first draw sampling, sequential sampling, random daytime sampling and flush sampling, in lead contamination detection. In 3 out of the 7 sampling locations without lead pipe, lead could not be detected (<1.1 μg/L) in most samples regardless of the sampling methods. On the other hand, in the 4 sampling locations where lead pipes still existed, total lead concentrations >10 μg/L were consistently observed in 3 locations using any of the four sampling methods while the remaining location was identified to be contaminated using sequential sampling. High lead levels were consistently measured by the four sampling methods in the 3 locations in which particulate lead was either predominant or comparable to soluble lead. Compared to first draw and random daytime samplings, although flush sampling had a high tendency to reduce total lead in samples in lead-contaminated sites, the extent of lead reduction was location-dependent and not dependent on flush durations between 5 and 10 min. Overall, first draw sampling and random daytime sampling were reliable and effective in determining lead contamination in this study. Flush sampling could reveal the contamination if the extent is severe but tends to underestimate lead exposure risk.