The Wastewater Treatment Plant needed to expand and upgrade their SCADA system. The main objective was to create a reliable network that incorporated existing equipment sites along with additional locations, while ensuring that scalable technology and bandwidth were available for future growth. Fiber was required in many areas because it was easier to deploy for longer distances throughout the facility, and it offered both immunity to EMI and RFI, while eliminating any potential for ground loops.

The most common communications protocol used in Ethernet networks is TCP/IP (Transmission Control Protocol/Internet Protocol). TCP/IP still permits the use of numerous protocols because messages using a specific protocol (such as Modbus or DF1) can be encapsulated within the TCP/IP packet. The flexibility of Ethernet protocols is crucial to its use in industrial networking, because it permits Ethernet networks to integrate existing devices and protocols by using serial device servers such as Moxa's NPort series, which allow serial network messages to be "wrapped" in an Ethernet packet, and transported across an Ethernet network. Basically, device servers convert serial data to Ethernet data, making it relatively easy to migrate from an existing serial network to a faster and more flexible Ethernet network.

The Carmel WWTU needed to network a combination of components within several existing and new buildings at their facility. However, the main objective at the plant centered around the industrial Ethernet network. The plant chose the EDS-726 26-port managed gigabit Ethernet switch for the Control Building because it provided multiple, easily-configured, modularized ports that support multimode fiber for the long distances necessary to cover the entire plant site.

Fiber optic connections provided speed and bandwidth that are orders of magnitude greater than twisted-pair. Equally important, fiber optic connections are not affected by EMI, RFI, lightning strikes, and other disruptions that could compromise both the performance and reliability of industrial networks.

EDS-726 can handle all of the PLC data collection needs required for central control by mixing and matching both copper and fiber ports while leaving room for additional expansion ports in the future. Although gigabit bandwidth was not needed at the time, EDS-726 offered the ability to utilize gigabit ports in the future as well.

In addition to EDS-726, the plant utilized a combination of managed EDS-508 and unmanaged EDS-308 switches for direct connections between PLCs, HMIs, and peripheral devices located in the other 7 buildings. These switches allowed 10/100 Mbps bandwidth, along with a combination of copper (RJ45) and fiber port (SC or ST) connections. The "plug & play" capability of unmanaged switches that use Ethernet along with TCP/IP connectivity sharply reduced configuration and reconfiguration costs.

The use of Simple Network Management Protocol (SNMP), universal in commercial enterprise networks, and other common Ethernet tools, allowed network managers to configure and monitor network performance remotely. This enabled them to identify potential problems before network capabilities were threatened. Furthermore, all of Moxa's managed switches offered excellent reliability via self-healing network recovery. When a fiber is broken, or a network switch fails, a Moxa Turbo Ring network will self-heal in less than 300 ms, even in a network that incorporates up to 80 switches. An additional benefit of a ring topology network is the reduced cost of network cabling compared with a Rapid Spanning Tree Protocol (IEEE 802.3D) network. By not requiring every fiber run to travel back to the control room, wiring a ring topology required far less fiber optic cabling, saving material and labor costs for the plant. In order to address security, the City of Carmel chose to use a combination of features available in Moxa's managed switches. Password Protection, Port Locking, MAC ID Filtering, and IP Masking were used to add security levels to the network.  The plant also has an A-B dial-up modem/router installed and has provided its IP address to all of the OEM machinery vendors with equipment on site.  When the OEM's require access, the plant can add their IP and unlock the MAC ID filter temporarily to allow them direct access only to their piece of equipment.  When finished, the plant reapplies the filter to prevent unauthorized access once again. Ultimately, the Moxa solution provided the facility with cost effective network redundancy and security between the Control, Biopast, Centrifuge, Return, and North Galley buildings, and the new Ultraviolet Building.