Comparison of 4 Different Flow Control Methods Of Pumps

Based upon the system head conditions, pumps may be able to pump at higher rates than needed when operating at 100% motor speed. This flow rate can be controlled by one of two ways, throttling the pump with a valve if the pump is a constant speed pump, or changing the motor speed with a variable speed drive. The former is only energy efficient if the higher flow operating point of the pump without throttling is to the right of the best efficiency point on the pump performance curve, and the throttling results in reducing the flow to a point closer to the best efficiency point on the pump curve. Otherwise, throttling the pump can result in using more energy than at the higher flow, as well as wasting energy because you end up using more energy than is needed. When the demand on the system fluctuates significantly, the pumping rate can be controlled automatically by varying the speed of the motor with a variable frequency drive (VFD), such that the pump output matches only what is needed to meet demands or the intended pumping conditions. The pump’s flow rate then increases or decreases based upon the affinity laws and the controlled speed of the motor. This way lower pumping rates can be achieved, which may result in lower efficiency than those at full motor speed; however, the energy consumption is still lower because the energy requirements to pump lower flows at lower heads are lower.

Calculator Tool for Determining Greenhouse Gas Emissions for Biosolids Processing and End Use

A greenhouse gas (GHG) calculator tool (Biosolids Emissions Assessment Model, BEAM) was developed for the Canadian Council of Ministers of the Environment to allow municipalities to estimate GHG emissions from biosolids management. The tool was developed using data from peer-reviewed literature and municipalities. GHG emissions from biosolids processing through final end use/disposal were modeled. Emissions from nine existing programs in Canada were estimated using the model. The program that involved dewatering followed by combustion resulted in the highest GHG emissions (Mg CO2e 100 Mg-1 biosolids (dry wt.). The programs that had digestion followed by land application resulted in the lowest emissions (-26 and -23 Mg CO2 e100 Mg-1 biosolids (drywt.). Transportation had relatively minor effects on overall emissions. The greatest areas of uncertainty in the model include N2O emissions from land application and biosolids processing. The model suggests that targeted use of biosolids and optimizing processes to avoid CH4 and N2O emissions can result in significant GHG savings.

Methane emission during municipal wastewater treatment

Study focused on amount of methane that is emitted from a plant, but also of the possible sources and sinks of methane on the plant. In this study, the methane emission from a full- scale municipal wastewater facility with sludge digestion was evaluated during one year.

Towards A New Decision Support System for Design, Management and Operation of Wastewater Treatment Plants for the Reduction of Greenhouse Gases Emission

This paper presents the development of an ongoing research project aiming at setting-up an innovative mathematical model platform for the design and management of WWTPs. The final goal of the project by means of this platform is to minimize the environmental impact of WWTPs through their optimization in terms of energy consumptions and emissions, which can be regarded as discharged pollutants, sludge and GHGs.

Energy Efficiency Drivers in Wastewater Treatment Plants: A Double Bootstrap DEA Analysis

The results show that the variables with a significant influence on efficiency are the chemical oxygen demand concentration; plant capacity; rate of used capacity, which positively affects efficiency; weight of industrial customers, which exerts a negative impact; and aeration system, with a negative impact for turbines. This article suggests the adoption of an effective control tool to monitor the costs, drivers and energy expenditure of water utilities.

Study of published WWTP energy data – more than 500 WWPTs

In this report representative  energy  data from several  countries was
gathered by  a team  to  create a  reference database. Best practises and
best-case scenarios for benchmarking were identified. The information was
retrieved from several sources such  as journals, reports,  direct  communication
with the stakeholders, mandatory EU registers etc. The team was able to
gather energy data from 588 wastewater treatment plants(WWTPs).

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