## 2 Materials and Methods
### Wastewater Treatment Plant Defining Problems and Weather Dependency  
Some of the defining problems that can be identified in a WWTP are:  
* Overloading of the plant: This can cause overheating of the blowers, which, in turn, causes a low-oxygen level in the bioreactor tank, thus reducing the efficiency of the secondary treatment stage. Plant overloading can also lead to sludge leakage from the settling tank.
* High substances consumption: For instance, the odor treatment process requires continuous adjustment of the used substances, depending on the input wastewater concentration and content. The wastewater content is highly dependent on the weather conditions.
* High energy costs: Around 30% of the annual WWTP operation costs is represented by the electricity consumption. Considering a developed country, an estimate of about 2-3% of the entire nation's electrical power is consumed for wastewater treatment. This can be significantly improved by optimizing the biological treatment processes.
* Equipment and/or algorithmic faults that can lead to various problems.  
* Undersized treatment plants: Most plants were developed 10-20 years ago, becoming undersized for the current loads since then, leading to the choice of increasing the load and costs in order to maintain a thorough cleaning process or discharging the partially treated wastewater to the environment and keeping the costs lower.  
A WWTP's operation is influenced by the weather conditions, the most significant being the precipitation amount. In case of very heavy rainfall, the WWTP may use the bypass channel, thus resulting in a high increase in operational costs (electricity and substances usage) or pollution. Even if the rain amount does not produce wastewater that can be legally sent to the environment after just primary treatment, the amount of rain highly influences the content and concentration of the wastewater present in the WWTP, which, in turn, influences the biological treatment that is applied in the secondary treatment stage and the chemical addition amounts and concentrations in the tertiary treatment. Besides rain, the temperature can also influence the WWTP, primarily from the odor treatment process standpoint, but also from the biological treatment in the secondary stage and sludge dewatering (when outdoor drying beds are used) processes standpoints. In addition, a storm or strong winds, particularly in the autumn, can generate large quantities of tree branches and leaves that can clog the screening filter during pretreatment.  
Considering the typical processes that take place inside a WWTP, the defining problems and the usual weather influence on WWTPs that were previously presented, the conclusion emerges that a WWTP represents the perfect environment that can benefit from a solution capable of identifying the exact dependencies and relations that exist between the measured characteristics of a WWTP and meteorological characteristics. Furthermore, using those relations and dependencies for predicting the future evolution of the plant characteristics can provide a valuable foundation for optimizing the WWTP in order to reduce costs, lower energy consumption, decrease substance consumption, and improve maintenance. Due to these considerations, although the implemented solution presented in the following section represents a generic approach, it was deployed for testing and validating purposes in a WWTP environment, where the potential to make an impact is considerable.