Performance evaluation and coefficients of reliability for waste stabilization ponds in northeast Brazil

This paper assesses the reliability of Waste Stabilization Ponds (WSP) and proposes an alternative approach to WSP design based on the calculation of coefficient of reliability (COR) from an acceptable measure of violation of discharge standards. For that, data were collected from 10 full-scale syst...

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Bibliographic Details
Published in:Revista ambiente & água 2021, Vol.16 (1), p.1-13
Main Authors: Alves, Matheus Sales, Silva, Fernando José Araújo da, Araújo, André Luís Calado, Pereira, Erlon Lopes
Format: Article
Language:English
Subjects:
Ammonia
Chemical oxygen demand
Coefficient of variation
Coefficients
Coliforms
Compliance
Discharge
Dispersion
Distribution functions
effluent quality
Effluents
ENGINEERING, ENVIRONMENTAL
Household wastes
Hydrologic data
Legislation
Mathematical analysis
Parameters
Performance evaluation
Ponds
Probability distribution
Probability distribution functions
Probability theory
Quality standards
Reliability
Reliability analysis
Solid suspensions
Stabilization ponds
Suspended particulate matter
Total suspended solids
Waste stabilization ponds
Wastewater discharges
Water treatment
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Summary:This paper assesses the reliability of Waste Stabilization Ponds (WSP) and proposes an alternative approach to WSP design based on the calculation of coefficient of reliability (COR) from an acceptable measure of violation of discharge standards. For that, data were collected from 10 full-scale systems operating in Northeast Brazil. All systems receive predominantly domestic effluent and are composed of one facultative pond and two serial maturation ponds. Different levels of restriction for effluent discharge were considered regarding the parameters: BOD, COD, total suspended solids, ammonia and thermotolerant coliforms. The Log-normal Probability Distribution Function (PDF) was able to represent the behavior of the concentration data in the effluent and, therefore, allowed the COR calculation. The COR was obtained from the coefficient of variation (CV) of the concentrations and the standardized normal variable associated with a 95% probability of non-exceedance. The observed dispersion of the results proved to be detrimental to the adoption of a single COR value for the evaluated parameters. In addition, the comparison between observed and design/operational concentration for optimal performance showed that the 95% reliability scenario represents a less achievable target for WSP systems.
ISSN:1980-993X
1980-993X
DOI:10.4136/ambi-agua.2571