Abstract:
The capital and operating costs associated with a small package plant MBR for smallscale domestic duty has been appraised based on a medium-strength municipal
wastewater. The three main membrane configurations were considered, these being
multi-tube, hollow fibre and flat sheet, with the most appropriate plant design chosen for
each configuration. The analysis proceeded via a consideration of the estimated amortised
capital costs of the plant individual components and their installation, coupled with
operating costs based largely on energy demand and residuals management. Energy
demand was calculated from aeration and pumping costs, with aeration based on a
combination of empirical relationships for membrane aeration and mass balance, and the
modified Activated Sludge Model version 2 used for estimating tank size and sludge
generation.
Results indicate that it is possible to produce a single household MBR at a capital cost
similar to the current market cost for package treatment plants. Desludging and
maintenance of these plants is similar but power requirements for an MBR are around 4
times that associated with more conventional package plants. Economies of scale exist
from 6-20 p.e. plants but above 20 p.e. there is little cost difference per head, due to the
design assumptions made. CAPEX and OPEX are to some extent interchangeable;
reductions in CAPEX are associated with an increase in OPEX and vice versa. Whilst
costs are high, the market for package MBRs is significantly influenced by the recycling
potential of the effluent produced.
A cursory comparison has also been made with conventional package plant treatment
processes.
