Demonstrating Cryptosporidium Removal using spore monitoring at lime‐softening plants

Because of their small size, Cryptosporidium oocysts cannot be easily filtered from water. This study evaluated the use of surrogates for measuring the microbial treatment performance of two point‐of‐use devices incorporating filtration with electrostatic charge interaction mechanisms. Both systems were challenged with Cryptosporidium oocysts (4‐6 μm), Bacillus subtilis (B. subtilis) spores (~1.2 μm), polystyrene latex (PSL) beads (~ 3 μm), Escherichia coli, and MS2 bacteriophage. The target biological contaminants were more effectively removed than the PSL beads, and the smaller B. subtilis spores mimicked Cryptosporidium oocyst removal more closely than the ~ 3‐μm PSL beads. Thus, surface charge appears to be an important factor for microorganism attachment, and B. subtilis spores should be considered a more appropriate surrogate than PSL beads for evaluating Cryptosporidium movement through charged media. For noncharged devices, PSL beads may still be useful as a surrogate for Cryptosporidium.

Section: Introductionmentioning

confidence: 99%

Evaluating surrogates for Cryptosporidium removal in point‐of‐use systems

Muhammad¹,

Sinha²,

Krishnan³

et al. 2008

“…IESWTR and LT2ESWTR differ on core treatment. Research data reported after the IESWTR was published indicated that treatment systems meeting the level of performance outlined in the IESWTR are capable of achieving removals approaching 4 log for Cryptosporidium (Cornwell, MacPhee, & Brown, 2001a and 2001b) or for aerobic spores (Cornwell et al, 2003). In fact, the instances when at least 3‐log Cryptosporidium removal could not be demonstrated were associated with conditions that either (1) would not have been in compliance with the IESWTR, e.g., effluent turbidity >0.3 ntu, (2) were intentionally conducted under suboptimal coagulation conditions, or (3) did not involve high enough raw water concentrations or low enough finished water detection limits to mathematically demonstrate 3‐log removal (Table 2).…”

Section: Lt2eswtr Regulatory Requirements Summarizedmentioning

confidence: 99%

“…At the time this article was written (March 2003), the LT2ESWTR had not been published in draft or final form and had not yet been subject to public review and comment. The following discussion is based on the best available data and includes information from presentations and peer‐reviewed documents prepared in conjunction with the AWWA Office of Government Affairs (Cornwell et al, 2003; Cornwell, MacPhee, & Brown, 2001a and 2001b).…”

mentioning

confidence: 99%

Applying the LT2ESWTR Microbial Toolbox at a Surface Water Treatment Plant

Cornwell¹,

Brown²,

MacPhee³

et al. 2003

Self Cite

The proposed and final versions of the Long‐Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) have not been published, but water suppliers are already gearing up for the challenges of compliance with the rule. This article discusses LT2ESWTR regulations in terms of their effect and implication for a surface water treatment plant. A case study applied the expected requirements of the LT2ESWTR to the Richmond, Virginia Water Treatment Plant (RWTP). The components of the microbial toolbox were analyzed in terms of cost, feasibility, and applicability to the Richmond facility. For RWPP, the most feasible and cost‐effective toolbox alternatives available were: a 0.5‐log credit for a watershed control program; a 0.5‐log combined filter effluent turbidity credit; a 1.0‐log demonstration of performance credit using full‐scale aerobic spore monitoring or pilot‐scale microbial challenge studies; and, inactivation with ultraviolet light. Although this study is specific to Richmond, the findings can be used by other utilities facing similar situations with similar alternatives available to them resulting from application of the microbial toolbox. This article is not available in its entirety in the printed issue of the Journal; only the expanded summary is available in print. The PDF of the entire article can be found on‐line at http://www.awwa.org.

“…These findings were the basis for the inclusion of aerobic spore monitoring at full‐scale facilities as an option for DOP credit in the upcoming LT2ESWTR. This is also the reason some utilities participating in the current project have already initiated spore monitoring as a tool to help them evaluate treatment plant performance (Cornwell et al, 2003b).…”

Section: Introductionmentioning

confidence: 99%

Using spore removal to monitor plant performance for Cryptosporidium removal

Brown¹,

Cornwell²

2007

Self Cite

Data from available literature indicate that Cryptosporidium oocysts are removed more efficiently than aerobic spore‐forming bacteria during water treatment processes involving clarification and filtration. Therefore, monitoring removal of naturally occurring aerobic spores can provide a conservative estimate of the potential for Cryptosporidium removal in full‐scale water treatment processes, which in turn can be used to establish the demonstration of performance credit allowed by the Long Term 2 Enhanced Surface Water Treatment Rule as well as to provide a valuable performance evaluation tool for water plant operators. The results from this study showed that (1) median raw water spore concentrations ranged from 300 to 3,000 spores/L for two lake sources and 80,000 to 400,000 spores/L for four river sources; (2) median filtered water spore concentrations rarely exceeded 5 spores/L, and these levels of removal were not apparently dependent on source water concentration; and (3) >4‐log spore removal could not be mathematically demonstrated unless raw water levels exceeded 10,000 spores/L (e.g., river sources).