Usefulness of networking in membrane plant design

and operation

J. Edward Burke', *Mike Mickley2, Jeffrey Truesdall2 , Robert L. Hamilton3

'City of Brighton, CO, USA

2 Mickley and Associates, 752 Gapter Road, Boulder, CO 80303, USA

Tel. (303) 499-3133; Fax (303) 499-5305

3 Hamilton Engineering Inc., 2543 S. Oneida Street, Denver, CO 80224, USA

Tel. (303) 757-7678

Abstract

The 10.0 mgd reverse osmosis nitrate removal plant in Brighton, Colorado, was successfully started up in November 1993. As a means of insuring that the plant design would not only meet current and future needs but would also avoid practical problems encountered by other plants, the city utilized a network of existing membrane drinking water plants. These were plants that had experienced similar treatment problems and challenges. This network, due to the openness and willingness of the other utilities to share information, insights, and experiences, provided considerable help in the design process. Details of the cost saving benefits of the networking experiences are presented. The membrane drinking water plant survey developed for and included in the American Water Works Association Research Foundation's publication Membrane Concentrate Disposal should be helpful in establishing a network for utilities considering membrane treatment.

1. What is a network?

A network in the present sense is a group of contacts that are linked together for the purpose of sharing information and supporting each other in mutually beneficial ways. The core of the network is a group of membrane drinking water utilities that share design, treatment and operation concerns. Some of these shared areas of concern are widely held, such as the quality assurance specifications for sulfuric acid, while others are of a more specific nature, such as how to deal with a certain type of fouling.

2. What is the need for and what are the benefits of a network?

The network is not a substitute for the role of the engineering firm. The authors wish to emphasize that they and the City of Brighton consider that the engineering firm did a very good job in the design process. However, one of the inherent realities with plant design is that the large engineering firms are not consistently at the plant site. As much as systems are engineered, checked and rechecked, frequently it takes an operator to catch oversights. As a reflection of this, some engineering firms are now hiring operators to check diagrams and systems.

The general benefit of a network to an individual plant is that it can provide a time and cost-effective means of assuring that the plant design meets the particular needs of the utility. By having access to the experiences of others who have gone through similar circumstances, the utility can avoid problems that are typical to new plants ( many times plants will have the same problems that another plant has had before).

*Corresponding author.

Further, the network provides an ongoing forum for the discussion, for sharing leads, ideas, tips, techniques and procedures that can contribute to the solution of problems that are encountered during the life of the plant. Indeed, the network can be useful during planning, piloting, construction, and operation of the plant during any development phase of the plant. Most of the networking benefits are ultimately cost benefits.

The network also affords benefits to the membrane drinking water industry. It provides another means of information transfer for sharing, contributing and documenting knowledge. In this regard it can be a more rapid means of gaining and sharing information as opposed to workshops, conferences and publications. Information transfer can lead to technological advancements as operators and others with solid ideas can impact the operation of other plants. Thus the specific benefits from networking include:

providing resources for feedback on planning alternatives

providing resources for help on chemical and equipment specifications

providing resources for help on design details and for facility and treatment processes

providing resources for post-start-up system critiquing

providing resources for help to address and solve operational problems and for obtaining operational hints

providing resources for keeping abreast of the latest developments in pretreatment and cleaning chemicals.

The network is a tool for the utility to use in addressing its responsibilities and, most frequently, a tool to reduce costs and keep them in control. Since there is a shared interest in designing, maintaining and operating a membrane utility plant, a network becomes a two-way means of receiving and providing assistance and support for utilities.

3. Network benefits to the City of Brighton

The following items were the direct or indirect result from visits by the City Council or by the Utility Director to several plant sites in Florida. During these visits the question was asked: "If you had to do it again, what would you change?"

Brighton requested an overhead bridge crane based on feedback from one plant. It has paid great dividends. It cut construction costs, and this cut the effective cost of the crane. The crane can be used to remove any piece of equipment or any pallet, and it facilitates getting inside the skid area.

Direct readouts in engineering units were located on each telemetry meter. This provides greater accuracy than the 0-100% scale, and it facilitates cross-referencing with the telemetry data, thus making calibration easier. Readouts were used for pressure, pressure drop and for flow measurements. In the case of a catastrophic failure of the telemetry computer, the readouts can be used as a manual back-up system.

Some valves were reduced in size allowing for better control of flow rates. Vertical cartridge filter vessels were used to avoid loading and cleaning problems associated with horizontal systems. More detail on some specifications resulted. As one example, Brighton now demands a full 40" membrane element and not two 20" elements spun together.

Many of the above insights to Brighton came from the Dunedin, Florida, RO plant.

Biological fouling was found during the pilot testing, and the network has helped Brighton to address this situation. A chemical company provided a list of three other plants having similar problems. From one of these plants (Arlington desalter, Arlington, California), a new antiscalant product was identified. It was bench tested at Brighton and found to work. Another plant that has a similar biological problem is conducting ongoing research just as Brighton is. The two plants keep in touch and share research results.

4. How to set up and use a network

The task is to identify existing membrane drinking water plants that have already encountered and dealt with the issues and problems that your utility is or will be facing. Potential contacts can be obtained from engineering firms, membrane companies, chemical suppliers or other groups and individuals connected in some way with membrane drinking water plants. This approach can be time consuming, and until a recent membrane drinking water plant database was published, it was the only approach available. This database is discussed in the next section.

Some utilities are open with their information and some are not. A clear explanation of the purpose and potential of the network and a willingness to share information with the contacted utility can help to establish the relationship on a solid basis. Participation in the network requires a utility to:

make many phone calls

be ready and willing to call these people and look for answers

be willing to say "we do have problems"

express an openness to talking to others and helping them with their problems - problems that you might have faced and solved

It is important to do the extra work for other utilities as they are going to do the extra work for you. Once the network gets going, it doesn't take that much extra time, and the benefits can be significant.

It is important to talk to operators (as well as managers) for the operators are the ones dealing with everyday problems. Early in the consideration of a membrane plant, it may be useful to visit the network sites. Later, once the plant is built, it may be helpful to have operators from other plants come in and critique the system.

The network may change with time as new mutually beneficial contacts are made.

5. The membrane drinking water plant survey

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