Category Archives: Taste and Odor

Taste Detection and Acceptability for Chlorine Residual, Bangladesh

Crider Y, Sultana S, Unicomb L, Davis J, Luby SP, Pickering AJ. Can you taste it? Taste detection and acceptability thresholds for chlorine residual in drinking water in Dhaka, Bangladesh. The Science of the total environment. 2017 Sep 20;613-614:840-846. doi: 10.1016/j.scitotenv.2017.09.135.

Chlorination is a low-cost, effective method for drinking water treatment, but aversion to the taste or smell of chlorinated water can limit use of chlorine treatment products. Forced choice triangle tests were used to evaluate chlorine detection and acceptability thresholds for two common types of chlorine among adults in Dhaka, Bangladesh, where previous studies have found low sustained uptake of chlorine water treatment products. The median detection threshold was 0.70 mg/L (n=25, SD=0.57) for water dosed with liquid sodium hypochlorite (NaOCl) and 0.73mg/L (n=25, SD=0.83) for water dosed with solid sodium dichloroisocyanurate (NaDCC). Median acceptability thresholds (based on user report) were 1.16 mg/L (SD=0.70) for NaOCl and 1.26mg/L (SD=0.67) for NaDCC. There was no significant difference in detection or acceptability thresholds for dosing with NaOCl versus NaDCC. Although users are willing to accept treated water in which they can detect the taste of chlorine, their acceptability limit is well below the 2.0mg/L that chlorine water treatment products are often designed to dose. For some settings, reducing dose may increase adoption of chlorinated water while still providing effective disinfection.

Cyanobacteria and Algae produce Odor-Causing Compounds

This paper states that algal bloom are a sign of anthropogenic disturbance. They actually can occur from natural eutrophication as well. The thesis of this paper is not quite clear from the abstract (rather eutrophic so to speak).

Lee J, Rai PK, Jeon YJ, Kim KH, Kwon EE. The role of algae and cyanobacteria in the production and release of odorants in water. Environmental pollution 2017 May 2;227:252-262. doi: 10.1016/j.envpol.2017.04.058.

This review covers literatures pertaining to algal and cyanobacterial odor problems that have been published over the last five decades. Proper evaluation of algal and cyanobacterial odors may help establish removal strategies for hazardous metabolites while enhancing the recyclability of water. A bloom of microalgae is a sign of an anthropogenic disturbance in aquatic systems and can lead to diverse changes in ecosystems along with increased production of odorants. In general, because algal and cyanobacterial odors vary in chemistry and intensity according to blooming pattern, it is necessary to learn more about the related factors and processes (e.g., changes due to differences in taxa). This necessitates systematic and transdisciplinary approaches that require the cooperation of chemists, biologists, engineers, and policy makers.

Chloroanisole Formation During Drinking Water Chlorination

Zhang K, Zhou X, Zhang, Mao M, Li L, Liao W. Kinetics and mechanisms of formation of earthy and musty odor compounds: Chloroanisoles during water chlorination. Chemosphere. 2016 Aug 22;163:366-372. doi: 10.1016/j.chemosphere.2016.08.051.

Chloroanisoles are often reported as off-flavor compounds which produce an earthy and musty flavors and odors in drinking water. To improve understanding and ultimately minimize the formation of 2,4-dichloroanisole (2,4-DCA), 2,6-dichloroanisole (2,6-DCA) and 2,4,6-trichloroanisole (2,4,6-TCA), which have low odor threshold concentrations (OTC: 0.03-4 ng L-1), a kinetic database for the chlorination of anisole was established by kinetic measurements. The results showed that HOCl reacted with anisole in acidic solution, with the hydrogen ion as an important catalyst. Quantification of product distribution of the produced chloroanisoles demonstrated that a chlorine attack in the para-position was favored over the ortho-position. A kinetic model was formulated, which permitted investigation of the relative importance of the chlorine dose and other water quality parameters including the concentrations of anisole and several metal ions, as well as temperature, on the product distribution of chloroanisoles. In general, high chlorine doses led to low concentrations of intermediates. The presence of ions such as Fe3+ and Al3+ facilitated the formation of chloroanisoles, but Zn2+ and Mn2+ did not. The kinetic model can be applied to optimize water chlorination and minimize earthy and musty odors.

Multi-barrier Treatment Approach Ensures Cyanobacteria and T&O Compound Removal

Zamyadi A, Henderson R, Stuetz R, Hofmann R, Ho L, Newcombe G. Fate of geosmin and 2-methylisoborneol in full-scale water treatment plants. Water research. 2015 Jun 27;83:171-183. doi: 10.1016/j.watres.2015.06.038.

The increasing frequency and intensity of taste and odour (T&O) producing cyanobacteria in water sources is a growing global issue. Geosmin and 2-methylisoborneol (MIB) are the main cyanobacterial T&O compounds and can cause complaints from consumers at levels as low as 10 ng/L. However, literature concerning the performance of full-scale treatment processes for geosmin and MIB removal is rare. Hence, the objectives of this study were to: 1) estimate the accumulation and breakthrough of geosmin and MIB inside full-scale water treatment plants; 2) verify the potential impact of sludge recycling practice on performance of plants; and, 3) assess the effectiveness of aged GAC for the removal of these compounds. Sampling after full-scale treatment processes and GAC pilot assays were conducted to achieve these goals. Geosmin and MIB monitoring in full-scale plants provided the opportunity to rank the performance of studied treatment processes with filtration and granular activated carbon providing the best barriers for removal of total and extracellular compounds, correspondingly. Geosmin was removed to a greater extent than MIB using GAC. Geosmin and MIB residuals in water post GAC contactors after two years of operation was 20% and 40% of initial concentrations, correspondingly. Biological activity on the GAC surface enhanced the removal of T&O compounds. These observations demonstrated that a multi-barrier treatment approach is required to ensure cyanobacteria and their T&O compounds are effectively removed from drinking water.

Algal Toxins Undetected in Findlay Drinking Water

“Tests of both treated tap water and raw water at the plant have shown no detectable signs of microcystin, the algae-related toxin that fouled Toledo’s drinking water supply Aug. 2-4, water treatment plant worker Jeremy Carter said.” click here

PEX Plumbing Releases Contaminants, Causes Odor

Kelley KM, Stenson AC, Dey R, Whelton AJ. Release of drinking water contaminants and odor impacts caused by green building cross-linked polyethylene (PEX) plumbing systems. Water Research. 2014 Sep 10;67C:19-32. doi: 10.1016/j.watres.2014.08.051.

Green buildings are increasingly being plumbed with crosslinked polyethylene (PEX) potable water pipe. Tap water quality was investigated at a six month old plumbing system and chemical and odor quality impacts of six PEX pipe brands were examined. Eleven PEX related contaminants were found in the plumbing system; one regulated (toluene) and several unregulated: Antioxidant degradation products, resin solvents, initiator degradation products, or manufacturing aides. Water chemical and odor quality was monitored for new PEX-a, -b and -c pipes with (2 mg/L free chlorine) and without disinfectant over 30 days. Odor and total organic carbon (TOC) levels decreased for all pipes, but odor remained greater than the USA’s Environmental Protection Agency’s (USEPA) secondary maximum contaminant level. Odors were not attributed to known odorants ethyl-tert-butyl ether (ETBE) or methyl-tert-butyl ether (MTBE). Free chlorine caused odor levels for PEX-a1 pipe to increase from 26 to 75 threshold odor number (TON) on day 3 and affected the rate at which TOC changed for each brand over 30 days. As TOC decreased, the ultraviolet absorbance at 254 nm increased. Pipes consumed as much as 0.5 mg/L as Cl2 during each 3 day stagnation period. Sixteen organic chemicals were identified, including toluene, pyridine, methylene trichloroacetate and 2,4-di-tert-butylphenol. Some were also detected during the plumbing system field investigation. Six brands of PEX pipes sold in the USA and a PEX-a green building plumbing system impacted chemical and drinking water odor quality.

Click here for full paper (fee).

Lake Turnover Causes Severe Taste and Odor Problems

“As hot days become cool nights in the Fall, water from the bottom of Lake Thunderbird rises to the top. It’s a process called “turning over,” now several Norman-ites are turning away from tastes terrible when this happens. But believe it or not the can still be safe to drink.” click here