Shewhart Control Chart in Microbiological Quality Control of Purified Water and its Use in Quantitative Risk Evaluation

Abstract

Water in pharmaceutical industry is a key ingredient in many industrial processes, including machine washing and preparation of most medicinal products. The process of regular monitoring for the microbiological quality of water at the points of use is a critical aspect in ensuring the compliance to the limit. However, the full value of the microbiological control could be accomplished by the use of control charts and statistical quality control to show the trend and behavior of bioburden. In addition, Shewhart charts provide insight for prediction of the future of the water quality. In the current study, purified water samples were analyzed microbiologically during a two-year period. The generated data were continuously interpreted using statistical software packages. The trend indicated that two regions in Shewhart chart were in the out-of-control state at these periods generating either out-of-trend (OOT) and/or out-of-specification (OOS). Investigations showed that these deteriorations in the performance were chronologically coincided with unusual rise in the microbial count of city water, although there was no direct correlation between the input and output water microbiologically. The rate of failure of product purified water was determined to be 7.69x10-4 and Ppk was 1.06 which were unsatisfactory performance. However, by removing the excursion periods due to the expected extraneous causes from the I-MR chart, a 337 times increase in the process performance was estimated with Ppk index of 1.53 and quantitative performance failure risk (QPR) equals 2.28x10-6. This finding highlighted the criticality of the quality of the feed city water and its impact on the final purified water. Thus, the processing stages in the water purification plant are not absolute barriers against microbial creeping into the distribution system, and the purification system of water has a certain tolerance limit after which an outbreak of microbial population occurs and hence compromising the system efficacy and performance. From the present study, it is recommended to design protective pretreatment system that buffers severe fluctuations in raw water quality so that water station possesses the ability to work optimally in an attempt of delivering safe water for medicinal and pharmaceutical manufacturing purposes.

Cite this work

No public copy is stored for this record, so only the metadata is cited.

Stored only when both papers are in the corpus — 8 citations exist upstream.

Papers that cite the same references — the relational fallback while embeddings are still backfilling.