MINLP Wastewater Stabilisation Ponds Synthesis using Rigorous Models under Different Scenarios

PAZ OCHOA, M.; ESTRADA, VANINA; HOCH, PATRICIA M.

Computer Aided Chemical Engineering

Elsevier B.V.

Año: 2016 vol. 38 p. 2103 - 2108

1570-7946

In this work, we formulate a network embedding rigorous models for three different types of stabilisation ponds (aerobic, anaerobic and facultative). The model is formulated as a mixed integer non-linear programming (MINLP) problem implemented in GAMS. The ponds are modelled taking into account mass balances for the main groups of bacteria, different types of organic load, algae biomass and nutrients. The objective is to synthesise and design the wastewater treatment networks (WWTN) that minimises the total annual costs, including operating and capital costs, subject to maximum allowable concentration of contaminant on the effluent in order to fulfil environmental regulations. The optimisation is performed under different scenarios of inlet concentration of organic load to take into account process uncertainty. For the base scenario studied, optimal configuration consists of a sequence of two aerobic ponds followed by a facultative one (aer-aer-fac), with recycle only in the first pond. System efficiency on COD removal is more than 65% with a total cost of USD 52,749. Scenarios? analysis shows that results strongly depend on inlet organic load concentration.