The paper presents the analysis of data related to the domestic wastewater characteristics from several areas situated in a large Brazilian city. Simple regression models are presented for the prediction of basic wastewater characteristics, such as water consumption (l/inhab.day), wastewater production (l/inhab.day),BOD load (g/inhab.day) and BOD concentration (mg/l). The models are based on simple socio-economic variables, with special attention to the easily obtainable variable of total family income (number of minimum salaries earned per month). Most of the models are able to give an excellent prediction of the desired wastewater variables. Additionally, the behaviour of the main wastewater characteristics according to the hour of the day and the day of the week are analysed. Based on the results obtained, it is suggested that the classical figures of BOD concentration of 300 mg/l and per capita BOD load of 54g/inhab.d do not apply to the typical population predominant in most areas of Brazil. The actual BOD concentrations are frequently higher than 300 mg/l, while the BOD load is frequently lower than 54 g/inhab.d. The results obtained can be used for design purposes in the areas studied, and possibly in areas of similar characteristics, substituting the classical figures obtained from foreign textbooks.

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