Exploring a New Approach of the Population Equivalent Concept through a Detailed Characterization of Grey and Black Waters

Abstract

Reliable and accurate data from on-site facilities are important for modelling the biochemical processes occurring in wastewater
treatment bioreactors. This study aimed to redefine the concept of population equivalent through a detailed analysis of grey and
black waters. The concept of population enables the determination of the overall pollutant load from various houses connected to
a collective treatment plant. Several chemical compounds and physicochemical parameters including lipids, total nitrogen,
proteins, carbohydrates, and total chemical oxygen demand (COD), were assessed in grey and black waters samples collected in
Belgium and Burundi, and expressed in population equivalent unit. Our results showed that the total COD corresponding to one
population equivalent unit in Burundi and Belgium was 117.08±10.09 g COD/capita/day and 138.75±20.09 g COD/capita/day,
respectively. The total COD in Belgian experiments was distributed as 34.26% for faeces, 19.01% for waters from kitchen sinks,
16.26% for the grey waters from the laundry, and 10.97%, 15.36% and 4.14% for toilet paper, shower soaps and urine,
respectively. Results from Burundi samples revealed that laundry detergents, toilet paper and shower soaps were 14.70±0.40
g/capita/day, 12.20±0.40 g/capita/day and 5.00±0.30 g/capita/day, respectively. The quantity of the main chemical compounds in
both grey and black waters ranged from 0.37±0.18 to 35.17±6.82 g/capita/day, with average values of 8.33, 10.37, 17.75, 12.27,
and 35.17 g/capita/day for lipids, total nitrogen, laundry detergents, proteins and carbohydrates, respectively. Our findings are
valuable information that can be explored for the determination of the "complex substrate biomole" formula, which is useful for
modelling the processes involved in wastewater treatment