1. Introduction With the increasing national investment in environmental protection and the deepening reform of the wastewater treatment industry, the operation and management of urban wastewater treatment plants are developing towards marketization, specialization, large-scale operation, and group-based development. Many professional operating companies need to operate and manage multiple wastewater treatment plants in the same city or different cities. Therefore, remote monitoring of the production and operation of wastewater treatment plants in different locations is of great significance for reducing operating costs, strengthening production management, ensuring the normal and efficient operation of wastewater treatment processes and achieving water quality standards for discharge, and improving the efficiency and quality of enterprise operation and management. 2. Current Status of Wastewater Treatment Plant Control Systems in China Currently, China's wastewater treatment automatic control systems mostly adopt distributed control systems (DCS) and fieldbus-based control systems (FCS). In DCS, the lower-level system uses PLC, and the upper-level system uses PC or IPC. The upper-level system collects process parameters, electrical parameters, and operating status information of major equipment in each process of the wastewater treatment plant through the communication network, and completes functions such as graphical display of equipment operating status, database management of production status, processing of detection data, and fault alarm. The lower-level PLC connects directly to the MCC cabinet, measuring instruments, etc., and can detect the operating status of each device and manage and control it, realizing the automatic operation of field equipment. A fieldbus-based control system is a system composed of a fieldbus, field intelligent instruments, PLCs, and IPCs. Field intelligent instruments, PLCs, and the monitoring unit are connected through a fully digital, bidirectional, multi-station communication network to form a fieldbus control system. This system is open and decentralized, achieving digital transmission at the fieldbus level, with high signal transmission accuracy, strong flexibility in field control, and ease of maintenance, representing the future trend of automatic control systems for wastewater treatment plants. Commonly used fieldbuses in wastewater treatment plants include Modbus, PROFIBUS, and AB's ControlNet and DeviceNet. Both of these control systems run monitoring and data acquisition software (SCADA), i.e., configuration software, on the monitoring unit to achieve real-time monitoring of the entire wastewater treatment process and equipment operating status. It displays the process flow in an intuitive screen, records online monitored parameters, equipment operating status, and processes, analyzes parameter change trends, promptly releases and forecasts operating conditions, and implements diagnostics and alarms. Currently, commonly used monitoring software for wastewater treatment plants in China includes FIFO, INTOCH, RSView32, and KingSCADA, but none of these programs currently offer remote control functionality. Since wastewater treatment plants are generally located far apart, achieving remote monitoring of their operations requires developing internet-based remote monitoring and configuration software, or using separate remote control software to remotely operate and communicate with the monitoring computers at the wastewater treatment plants. 3. Remote Monitoring Principles Remote control refers to managers connecting to a remotely controlled computer via WAN, LAN, or both computers having internet access. This allows them to display the desktop environment of the remote computer on their own computer and perform configuration, software installation, and modification tasks on the remote computer from their local computer. The basic functions of remote control include: remote control, file transfer, remote screen browsing, keyboard interaction, internet connection, and even voice communication. 4 Functional Requirements of Remote Monitoring System for Wastewater Treatment Plants Given that the scale of production equipment in wastewater treatment plants is not very large, and generally only one or two monitoring machines and one management machine are set up in the central control room, the remote monitoring system should mainly have the following functions: (1) Remotely monitor the process flow of the wastewater treatment site. The remote monitoring terminal should be able to grasp the process operation data of the wastewater treatment plant in real time, including the operating status of the main production equipment such as lift pumps, bar screens, aerators, sludge bridges, and sludge dewatering machines, as well as the real-time data of various water quality detection sensors and instruments. (2) Record and save various historical data of the wastewater treatment process. This includes the running hours of each equipment, the detection instrument data of each process structure, the water quality data such as COD and BOD5 of the influent and effluent submitted by the laboratory department, as well as the operation duty records, equipment maintenance records, etc., so as to facilitate the integration with the ERP system of the operation and management company. (3) Alarm prompts and fault diagnosis. The remote monitoring terminal should obtain the alarm information of the equipment and instruments at the wastewater treatment site in real time, and be able to confirm and reset them. The remote monitoring engineer can provide solutions and plans. (4) Login Security Assurance. The legitimacy of user login and operations is ensured through data encryption, digital signatures, authentication, IP filtering, security alarms, and login logs. 5. Development Models of Remote Monitoring Software Currently, there are two main remote monitoring solutions: client/server (C/S) based and web-based. The C/S-based remote monitoring model includes a client program and a server program, and is widely used. The C/S model generally uses socket programming technology to establish the client and server sides. It is the most common programming model in network programming technology and is also suitable for remote monitoring of sewage treatment plants. The server adopts a multi-threaded working mode, listens for and receives client requests, and then collects and analyzes data from the controlled objects on site. The client is responsible for establishing a connection with the remote server. Their communication part uses socket programming and can be based on protocols such as netbeui, netbids, ipx/spx, tcp, or udp. The server program is placed on the controlled computer, and the client program is installed on the control end. After successful installation, the server program automatically collects information from the target computer, including IP address, network environment, OS environment (and even the superuser password). It then encrypts the obtained data to form special confirmation frames, which are repeatedly sent to the client program's computer (or another virtual address space) to request a controlled connection. After successful installation, the client program collects the confirmation frames sent back by the server program over the network, selects and configures the appropriate network protocol according to the environment parameters in the confirmation frames, and finally sends connection and control commands to the remote computer. Once the two computers are connected, the client program sends instructions to the remote computer according to the operator's intent and is responsible for reproducing the remote computer's screen status on its local machine based on the data information sent back by the server program. The server program then completes a series of process operations and data transmissions according to the instructions. With the continuous development of internet technology, remote monitoring solutions based on web technology are increasingly demonstrating their superiority. Web technology adopts a three-tier architecture, eliminating the need for direct communication between the client and server, thus reducing the burden on both. Based on the HTTP protocol and implemented using HTML and Java technologies, web technology offers advantages such as simplicity, efficiency, and cross-platform compatibility, making it a promising technological direction for the development of remote monitoring and configuration systems for wastewater treatment plants. When a remote monitoring terminal needs to acquire on-site monitoring data, it first connects to a web server. This server then interacts with the specific monitoring equipment via CGI, ISAPI, or even Java applets, enabling the remote monitoring terminal to monitor the wastewater treatment process in real time using a standard web browser. 6. Application of the Remote Control Software PC Anywhere Due to differences in the control systems and monitoring software used by various wastewater treatment plants, it currently requires significant investment to adopt the same system with remote monitoring and configuration functions across multiple wastewater treatment plants within an operating company. Software development also presents certain challenges. In recent years, with the development of computer network technology, some excellent remote control software has emerged. PC Anywhere, developed by Symantec in the United States, is a typical example. Practice has proven that this software is easy to operate, stable and reliable, and highly secure, making it suitable for remote monitoring of urban wastewater treatment plants. The method of using PC Anywhere to achieve remote monitoring of wastewater treatment plants is as follows: PC Anywhere software is run on both the remote monitoring terminal and the wastewater treatment plant monitoring machine (the controlled end). PC Anywhere establishes a connection between the two computers via the internet or LAN. The remote monitoring computer transmits the keyboard and mouse input information from the remote monitoring user via a network line as input to the wastewater treatment plant's monitoring machine, controlling its operation. Simultaneously, the controlled monitoring machine transmits its screen image to the remote monitoring computer's monitor in real time. This allows the remote monitoring computer to remotely control the wastewater treatment plant's monitoring machine. The remote monitoring user can perform operations such as input, display, transmission, and even printing as if sitting in front of the monitoring machine. PCAnywhere selects the connection method based on the operating environment of the remote monitoring end (master control end) and the wastewater treatment plant's monitoring machine (controlled end), as shown in the attached table. With the continuous reduction of network communication costs, it is ideal for both the master control end and the controlled end to use ADSL broadband access to the internet. Besides enabling remote control of remote PCs, PCAnywhere also provides online services, gateway services, file services, and printing services; it offers a scripting command language that allows for programming of certain frequent operations, providing strong process control capabilities, which is more beneficial for the production operation management and daily affairs handling of wastewater treatment companies. pcanywhere provides the following comprehensive security mechanisms to ensure the security of remote monitoring of wastewater treatment plants: * **Keyboard locking on the controlled host after connection establishment:** This prevents nearby users from viewing the session but hindering their input. * **Screen display shutdown on the controlled host:** This prevents unauthorized viewing during remote control. * **Access account and password:** Accounts and passwords are created for authorized remote users. * **Password reconnection:** A password is required upon reconnection after an unexpected session interruption. * **Auditing of failed connections:** The maximum number of login attempts and the longest login time are recorded. * **Data encryption:** All data transmitted during the session is encrypted using a specific method. * **Automatic connection termination after a set period of inactivity:** For detailed instructions on using pcanywhere software, please refer to its user manual. The author conducted a remote monitoring practice of a wastewater treatment plant using PCAnywhere software. PCAnywhere software was installed on the remote monitoring machine in the company's technical department (master control end) and the monitoring machines in the central control rooms of the two wastewater treatment plants operated and managed by the company (controlled ends). Both the master control and controlled ends were connected to the internet via ADSL broadband. Practice proved that the superior performance of PCAnywhere software and the ADSL network speed fully met the requirements of remote monitoring of wastewater treatment plants. Technicians could conveniently and quickly operate the controlled monitoring machines through the master control computer, thereby obtaining various required production data, operating status, and parameters. They could directly control the start and stop of equipment and perform remote fault diagnosis based on various alarm information, fully meeting the needs of remote monitoring and management of wastewater treatment plants. The entire project implementation cost was less than 10,000 yuan, achieving a relatively ideal remote monitoring effect. 7. Conclusion Implementing remote monitoring is an urgent need for the marketization of wastewater treatment plant operation and management. Adopting monitoring and management software with remote monitoring functions in wastewater treatment plants is the future trend. PCAnywhere software is cost-effective and a good remote control implementation solution.