O & M Practices for Sustainable WWTP Operations
Nitin Verma, Environmental & Clean Technologies Expert Spans Envirotech Pvt Ltd
Jahanvi Kulshreshtha, Water/Wastewater Process Engineer, Spans Envirotech Pvt Ltd

A report on Super ESPC suggests that 21 percent of reported savings could be achieved by reductions in Operation and Maintenance (O & M) costs which can be achieved through sustainable design and good O & M practices. The authors , in this article, delve in depth over adopting efficient O & M practices for sustainable Wastewater Treatment Plant (WWTP) Operations across the functions of Operations, Maintenance, Engineering Support, and Training Administration to achieve significant cost reductions.

Wastewater treatment projects would typically have a cost structure as shown in figure 1. It indicates that 'O & M costs' form a significant portion of the total project cost and that 'engineering' - which form small portion of overall project cost - can bring down the entire project pyramid if not carried out efficiently. On dissecting the O & M costs, it is typically found that manpower, power and chemical costs account for about 80 percent of the annual O & M costs. (The percentage for each cost element is expected to vary primarily because of technology adopted, project size, location & environmental regulations (for example: sludge disposal norms). Hence, the cost savings can be achieved by adopting good design and O & M practices.)

O & M costs can constitute a substantial portion of a project's savings. A report on Super ESPC (Energy Savings Performance Contracts, 2007) projects shows that 21 percent of reported savings were due to the reductions in O & M costs. By adopting good and sustainable design and O & M practices, we can reduce manpower, power, chemical and residual disposal costs. The overall O & M programme in any organisation typically consists of five distinct functional groups that includes Operations, Maintenance, Engineering Support , Training, and Administration.

For sustainable O & M management, each of the functions must put in their best efforts. However, the key to effective system lies not only in individual best efforts but largely in coordination among them and integrating them all together. (Read the sample cases in the Fact Box on next page)

Strategies to Improve O & M Processes
Following are some uncommon points which should be considered while planning strategies for an effective O & M system.

Data Usage
  • Data collected through laboratory analysis and other indicators for power consumption, flow, drive run time etc is generally not analysed and utilised for process optimisation after a project is completed. Inferences from the analysis of data can be used to operate the plant more efficiently, design a preventive maintenance schedule as well as energy and water conservation models.
  • Data acquisition systems can be installed along with remote monitoring systems.
  • A feedback loop from ground level operators to manger and expert level is crucial.
  • Constant O & M supervision from designers and experts.
Smart Working and Task Rotation
  • There should be rotation of tasks among various operators so that monotony can be avoided and help operators keep interest in what they are doing and give them the opportunities for career growth.
  • Laboratory testing schedule should be planned with the focus on obtaining high quality data and analysing the same rather than too much data which is seldom analysed. For example, there is no need to conduct BOD examinations daily when a much simpler COD test gives faster and more accurate information about water quality and pollution.
  • Standardise processes and use a centralised database for all facility related data. Facility management software tools are now available that seamlessly integrate all facility data on a single platform. For example,
    Cloud-based Facility Management System applications are available in the market as Software-as-a-Service (SaaS) at nominal monthly subscription fees.
Performance Level Benchmarking
  • Intra and inter-organisation benchmarks should be defined and put as target for the employees both internal as well as outsourced. For example, effluent produced per kg of produce, energy used per m3 of wastewater treated etc.
  • Target once achieved should be maintained and benchmarks should be upped regularly.
  • Practices should be as per standard operating procedure or O & M literature provided by the manufacturer or designer. These documents should be readily available to all operators and not archived in a library.
  • Performance can be monitored keeping the following criteria in mind:
    • Energy Efficiency
    • Water Recovery
    • Chemical Usage
    • Down time of any asset
    • Frequency of troubleshooting requirements per year
  • Depleting water resources have created a necessity to deploy skilled operators to utilise assets efficiently. It is necessary to train operators and establish a grading and reward programme to ensure a competitive environment and continuously improving system.
Automation Alternatives for Performance Improvement
Supervisory Control and Data Acquisition (SCADA) systems are utilised for remote data acquisition and real-time control, whereas Data Acquisition Systems (DAS) are simply for one purpose only, i.e. Data Acquisition. Most WWTPs employ a SCADA system to operate and monitor their process plants; however, the level of automation is restricted to more or less data acquisition. Any utility going for a SCADA system mainly for data acquisition makes significant compromises to use it for this purpose. These compromises include cost, data integrity, flexibility, convenience and control of the task.

It is important to first understand that DAS and SCADA systems are architecturally different types of systems. SCADA is a real-time system requiring a continuous channel of communications between the host computer and each I/O device (Remote Terminal Unit (RTU)). In data acquisition applications, the RTU responds to requests for real-time measurements from the host computer. If monitoring a field parameter (e.g. level, flow or pressure) once every five seconds is important, the host computer sends a request for these parameters every five seconds.

SCADA systems operate in this fashion because when performing their primary function, which is control, they make real-time decisions at the host-based on real-time data collected from all field sensors. However, when a SCADA system is used for data acquisition only, particularly for remote monitoring applications, this approach of real-time monitoring of parameters is not optimum or even practical because of system complexity, cost and data reliability exposure.

A dedicated DAS, however, is optimised for remote monitoring and comes at a much lower cost. A DAS is typically independently configured to store both manually entered data (e.g. laboratory testing data) and also sample each field sensor or instrument at a practically optimum rate for that parameter.

Some Key Advantages of a Cloud-based DAS:
Following are some of the key benefits of a cloud based DAS system that can be easily integrated to meet the specific requirements of any utility:
  • The cloud platform is customisable to meet each utility’s particular requirements
  • Data centre delinked to the control system significantly reducing plant operations risks due to network hackers
  • Complete consolidation of all water quality data and asset operations data
  • Simultaneous access to all current and historical data
  • Access to your data anytime, anywhere and from any web enabled device
  • Operators and consultants can use the platform for performance enhancements and troubleshooting.
  • Store all plant related information including As-Built Drawings, water quality reports, O & M Manuals etc at an easily accessible location.
  • Reduction in data errors
  • Easier and faster access to relevant monitoring data
  • Reduction of time and effort to verify compliance and produce reports
  • Fully customisable and automatic email alerts
  • Allow comparing data between various utility assets within an organisation and establish benchmarking systems
  • All data is stored on a secure encrypted database and has backup so that you will never lose any data
This methodology provides the user the best of all data worlds: the cost, versatility and reliability of a cloud-based DAS system – and all their plant and field data on a common platform.

A major part of the life cycle cost of an asset is spent on periodic maintenance and proper operation which helps in increasing the life of the asset and thereby the project costs.

We believe the 1st step towards better O & M management is to know what to measure, then measure and subsequently use the data for optimisation. As more and more WWTPs are designed for wastewater reuse and/or as ZLD projects , the importance of energy, chemical and waste solids disposal cost optimisation would greatly increase.

Secondly, it is critical to ensure full alignment of interests at all functional levels and individuals. Operators, managers and engineers must feel adequately motivated and incentivised to ensure that they continually work towards improving the O & M and also the design of new systems and their performance adds value towards their personal career development.

Following are some sample cases where lack of performance and the necessary coordination became apparent and led to loss of output and/or higher O & M costs.
  1. Replacement of Diffusers: The WWTP operations team notices that diffusers in one of the aeration tanks say Aeration Tank No 1 (out of a total of 2 aeration tanks) are damaged and need to be replaced. They pass on the message to the engineering team who initiates a purchase and replacement order to an outsourced maintenance team. When the diffusers reached the site, it was found that the diffusers ordered were of a different type that were installed in Aeration Tank No 2 and thus had to be sent back and a new purchase order had to be initiated. Because of this there was not only loss of time during which the WWTP ran inefficiently, but also posed a significant risk of failure to meet the discharge parameters .
    Solutions: Diffusers installed in all aeration tanks must be of the same make and type. Hence, no confusion would be created during replacement.
  2. Asset Life: The operator claims that he ran two blowers for the aeration tanks for more or less the same amount of time. However, in realty the night operator forgot to switch on the blowers and because of which one blower on average ran for 30 per cent more and hence has to be overhauled or replaced sooner.
    Solution:This could be avoided if the data acquisition of the blower run times was automated and/or the manager got accurate data from the operator.
  3. Electricity and Chemical Consumption: A new WWTP operator has been dosing higher than required amount of chemicals at the WWTP and/or running a pump more than required (e.g. sludge re-circulation pumps) or running a very old pump which should have ben replaced than being operated. However, no action is taken as this information is seldom presented to the engineers in a timely manner or in the right format.
    Solution: This can be avoided and more optimum steps can be remotely initiated by a team of experts based on factual data by adopting a consolidated data management system.
  4. Design Improvements: WWTP at manufacturing plant in Delhi has adopted a particular type of pump which the plant operators find to be inefficient but there is no/little feedback given to the projects team who are setting up a new plant in Mumbai and as a result the Mumbai team again installs the same make and model of the pumps.
    Solution : Such events can be efficiently captured if operations and maintenance data is captured and stored from older plants and made available to the design and project teams who can use the data for improving designs of new plants.
  5. Under qualified operators: Many WWTP operators are under qualified and do not have the necessary understanding and/or expertise in operating WWTP, especially during changing inlet quality and other process parameters. On the other hand hiring experienced operators can increase the manpower costs. Most WWTP managers have to grapple with this problem and many a times the hiring decisions are sporadic in nature.
    Solution: It is necessary to invest in regular training of operators which can be provided using virtual classrooms, shadowing, regular rotation etc. Further, it is also critical to ensure a seamless interaction medium is provided between the operations staff and engineering staff to address any technical queries of the operators.
The above cases are only some common examples of on-ground challenges that lead to inefficient operations of WWTPs. The common theme that typically emerges is accurate data unavailability, lack of factual data use for optimisation of the various O & M processes and the lack of a positive feedback loop between operators and designers.