Guidance Book for Management of Raw Water Turbidity Fluctuations and a Series of Water Treatment Workshops

Transcription

1 Guidance Book for Management of Raw Water Turbidity Fluctuations and a Series of Water Treatment Workshops Hideaki Hoshi*, Masao Tomii *, Takako Aizawa*, Shigeru Ando* and Fumio Sasaki* * Japan Water Research Center, Toranomon Denki Bldg 2F, Toranomon 2-8-1, Minato-ku, Tokyo Abstract In the past ten years, the Japanese water utilities have undergone four to forty-five water quality incidents a year due to fluctuations in the source water turbidity. In some cases the incidents led to a major disruption of the local water supply. These incidents were primarily caused by a turbidity spike in the surface water due to intense rains, which are occurring more frequently in recent years. In addition, negative impacts from the turbidity spike have been worsened by chronic problems facing many small utilities, including a shortage of operators and a deterioration of aging facilities. In this background, the Japan Water Research Center (JWRC) has developed the Guidance Book for Management of Raw Water Turbidity Fluctuations. Intended to be particularly useful to the small utilities, the guidance book helps in dealing with high turbidity raw water as well as in understanding the basics of turbidity management in general. Also, to promote the use of this guide book and to assist utilities in mitigating their difficulties associated with water treatment, JWRC has also hosted a series of water treatment workshops at local water treatment plants in different parts of Japan. Keywords small water utility; water treatment; high turbidity; guidance; workshop 1. Background and Objective In the past ten years, the Japanese water utilities have undergone four to forty-five water quality incidents a year due to fluctuations in the source water turbidity. In some cases, a raw surface water with an unprecedented level of turbidity led to a major disruption of the local water supply. The occurrence of such incidents can be partly attributed to heavy rain events due to unusual weather patterns and a degradation of river s. On the other hand, the negative impacts from the turbidity increase seem also worsened by chronic problems facing many small utilities, such as a shortage of plant operators, deterioration of aging water facilities as well as financial constraints. A questionnaire survey by the Japan Water Research Center (JWRC) also shows that not a few utilities are facing challenges such as a lack of proper operation manuals and a poor execution of coagulation and sedimentation process. In this background, JWRC has developed the Guidance Book for Management of Raw Water Turbidity Fluctuations. The guidance book is designed to assist in coping with high turbidity raw water. It also aims to help inexperienced operators by showing the basic requirements and principles in the turbidity management in general. Also, using this guide book, JWRC has hosted a series of water treatment workshops in different parts of Japan. With the aim of helping small utilities, the workshop intends to mitigate their difficulties associated with water treatment, providing an opportunity to learn from other utilities and to deepen their understanding about the water treatment process in general, as well as to build a network with other utilities. 2. Guidance Book for Management of Raw Water Turbidity Fluctuations (1) Key Concept of the Guidance Book The guidance book was developed based on the following concepts. Expected outcome: for utilities to be able to recognize current operational difficulties and start working on mitigation by themselves Target utilities: small water utilities Target water treatment process: flocculation/sedimentation/rapid filtration Target audiences: water utility director, water treatment plant manager, senior operator 1

2 (2) Organization and Contents of the Guidance Book The Guidance Book consists of three sections. (A) Manual of Turbidity Management in Water Treatment describes the basic requirements and procedures for an effective turbidity management. (B) Main Points for Management of Raw Water Turbidity Fluctuations visualizes the overall process of managing turbidity fluctuations. (C) Commentary for Management of Raw Water Turbidity Fluctuations describes the basic principles and recommended technologies for turbidity management. (A) Manual of Turbidity Management in Water Treatment The manual describes the basic requirements for the turbidity management in a rapid filtration process (Figure 1). The manual is practical to use, showing a method of water quality management, necessary responses in case of an insufficient treated water quality, ways to control ph values and alkalinity that could adversely affect the coagulation process, necessary steps and procedures to enhance a coagulation and sedimentation process, and examples of relevant troubleshooting. So that it can be used by as many utilities as possible, the manual is made not too specific in their descriptions. Therefore, each user would need to consider the guidance in their own context. Pre chlorination Pre alkali (Pre acid) Coagulant Secondary chlorination (Secondary coagulant) Tertiary chlorination (Secondary alkali) Intake from river Receiving well Chemical mixing Flocculation Sedimentation Filtration Clear water tank Distribution reservoir * The use of a rapid coagulation and sedimentation is also assumed for the portion from the chemical mixing to the sedimentation. Figure 1. Assumed water treatment process involving a rapid filtration (B) Main Points for Management of Raw Water Turbidity Fluctuations The main points of the (C) Commentary for the Management of Raw Water Turbidity Fluctuations were summarized in a poster format to provide an overview of the turbidity management. The summary is expected to be printed and mounted on the wall of a workplace so that relevant staff can take a look and easily understand the operational flow. For an improved usability, the poster-format summary was prepared in two types for the plant operator and the utility manager. (C) Commentary for Management of Raw Water Turbidity Fluctuations The commentary is designed to be a reference for utilities in developing an operational plan to address turbidity fluctuations. Intended for the water treatment system with a rapid filtration, the commentary consists of Chapter 1 to 7 as is shown below. Chapters 2 to 4 help the reader understand current issues and weak spots while assisting in their mitigations. Chapter 5 to 7 discuss concrete methods to address raw water fluctuations while showing various tools that would be useful. 2

3 Chapter 1: Review Chapter 1 describes the objective and basic principles of the guidance book as well as discussing the necessity of a proper management by citing related water quality incidents in the past Chapter 2: Basic requirements and evaluation of current status for addressing raw water turbidity fluctuations Chapter 2 shows a flow chart (Figure 2) and basic requirements to be considered when deciding an operational policy to address raw water turbidity fluctuations. The chapter also provides a user friendly check sheet to evaluate the current management status of the utility. Chapter 3: Basic knowledge (influence of rain-induced water quality fluctuations on water treatment and distribution) Chapter 3 shows the basic information the user needs to know about the coagulation and sedimentation process, the management of filtrate water, etc. Chapter 4: Advance preparations and management in non-emergency situation Chapter 4 describes the necessary preparations (evaluation of the existing system and the current management status, establishment of a proper organizational structure, development of operation manuals), examples of a capacity enhancement by making minor changes to the system, and the basic requirements for the daily management. Chapter 5: Response to raw water fluctuations Chapter 5 describes the necessary responses to be made when an increase in turbidity is anticipated or occurring or when the water supply could be disrupted. The chapter also describes what to do when the filtrate water shows a higher level of turbidity than usual. Chapter 6: Response after the turbidity is back to normal Chapter 6 discusses an evaluation of the response made, coordination with relevant entities, a future consideration for introducing additional measures (e.g. facility upgrade), etc. Chapter 7: Technical aspects Chapter 7 provides information regarding: an information collection for an early detection and prediction of raw water quality fluctuations, points to note for inexperienced operators regarding the water quality measurement, a management method when automatic gauges are not available, and the necessary measures to be taken to improve a coagulation and sediment process. 3

4 Response during non-emergency Manual Daily operation Record & analyze Increase in raw water turbidity occurs or anticipated upstream of the intake station Understand situation Auto measurement Collect info Estimate impacts (raw water quality, distribution amount, etc) Evaluation for improvement Judge Respond <Before raw water quality deteriorates> Establish emergency organizational structure, fill backup reservoirs, etc. <After raw water quality deteriorates> Reinforce water treatment process, suspend intake, etc. (Enhance monitoring) (Back to normal) Response to raw water turbidity fluctuations Figure 2. Response flow to raw water turbidity fluctuations 2. Water Treatment Workshop (1) About the Workshop The water treatment workshop is primarily designed for utility staff members. The event aims to help utilities mitigate the difficulties in their water treatment and provide an opportunity to exchange opinions and build a network with other utilities. The workshop was held 11 times from 2014 to 2016 with a total of 212 participants from 150 utilities. Of them, more than 50% (107 people) were from small utilities (92). 30% of the participants had less than five years of work experience and 15% were aged under 30 years old. The workshop consists of an opinion exchange session among participants, a guidance book-based lecture and discussions, as well as a tour of a water treatment plant. During the exchange of opinions, the participants were divided into groups based on the watersheds and current operational challenges they share. One group was made of eight persons. For every group, a JWRC facilitator and the participants discussed the group s challenges and potential mitigation measures. The common theme of the lecture is how to cope with turbidity fluctuations in raw water. According to the geographical area where the workshop was held, the content of the lecture was adapted to reflect the local issues and expected needs of the participants, focusing on the case studies of turbidity-related incidents that happened in the past in a similar context. 4

5 At the tour of a water treatment plant, the plant s operators gave the participants a walk-through of the facilities, while JWRC staff played a supporting role by explaining basic knowledge of water treatment such as an optimum ph range for coagulation, as well as comparing disparities between the plant and other plants using different equipment and facilities. In this way, participants could consider if there is room for improvement in their own water treatment process. (2) Challenges raised in opinion exchange session The current challenges facing the participants were shared in the opinion exchange session. In descending order, the most common challenges were: water treatment skills and techniques, source water quality (other than turbidity), operation and maintenance of facilities and succession of skills and technical expertise (Figure 3 and Figure 4). A comparison by the size of the utility shows that large utilities are more concerned than small utilities about water treatment skills and techniques and source water quality (other than turbidity). On the other hand, small utilities are more concerned than large utilities about operation and maintenance of facilities and succession of skills and technical expertise (Figure 3). Also, a comparison by the work experience of the participant shows that the people with more than five years of work experience are more concerned than the people with less than five-year experience about water treatment skills and techniques and source water quality (other than turbidity). The ratio of concern about operation and maintenance of facilities and succession of skills and technical expertise are almost the same for the two groups of different work experiences (Figure 4). In the session, it was also found that small utilities rarely afford to do more than a daily operation of facilities and a routine test of water quality against the drinking water quality standards. In small utilities, staff members often do other administrative tasks of that municipality in addition to water supply management. Also, they might be involved in water services just for a few years before getting transferred to other departments. Such a reality makes it difficult for small utilities to train young water professionals that could be a vital part of their services in the long term. (3) Measures to mitigate operational challenges From the information exchange at the workshop, we found that operational challenges facing the participants/utilities vary. Their level of understanding for the current challenges also varied depending on the size of the utility and the number of work experience. As for the participants from small utilities, their challenges were primarily related to the use of water treatment technology, operation of facilities, and succession of technical expertise to younger operators. We also found that it was especially demanding for utilities with a limited number of operators or young staff members to effectively respond to water quality fluctuations, which have been observed more often lately in relation to unusual weather patterns and natural disasters. It was also discovered that there were many challenges utilities could not overcome single-handedly. If related situations are to be improved, a more active engagement by policy makers at the regional and/or national level would be necessary. At the same time, it would also be essential to build a communications network among neighboring utilities so that they could help one another through an exchange of relevant information as appropriate. This type of network would also be effective for a successful succession of technical expertise to younger staff members. 5

6 Figure 3. Challenges presented by workshop participants according to the size of utility Figure 4. Challenges presented by workshop participants according to the work experience 6

7 3. Conclusions Some of the operational challenges faced by small utilities could be mitigated by knowing how other utilities have been addressing similar issues. For this reason, the workshop proved useful to the participants as was demonstrated in the post questionnaire survey to the participants. JWRC will keep on hosting the workshop while refining its contents based on the feedback received. As a related activity, JWRC is now conducting case studies on some of the difficulties with water treatment presented during the workshop. The objective is to find mitigation measures by visiting various water treatment plants to understand the characteristics of their facilities, source/ treated water qualities and the operational status. Through a close cooperation with utilities and other stakeholders, JWRC will continue its effort to provide assistance for small utilities. Acknowledgements The development of the guidance book was a result of the "Research on Response to the Degradation of Raw Water Quality at Aging Water Treatment Plants" which was carried out by JWRC from FY 2011 to FY 2012 with a grant-in-aid for scientific research from Japan s Ministry of Health, Labour and Welfare. The authors would like to express their sincere gratitude to the co-researchers from other organizations and to the numerous water utilities that took part in the related surveys and reviews. We would also like to thank the utilities and other entities that gave their generous support in our organizing the workshop in various areas. References 1)Aizawa, T. et al Guidance Book for Management of Raw Water Turbidity Fluctuation. Japan Water Research Center (in Japanese). 2)Kousaka, Y. et al Water Treatment Workshop to Support Small Utilities (II). Proceedings of the Annual Research Conference in FY 2016 of the Japan Water Works Association (in Japanese). 7