Characterisation and biodegradation of settleable organic matter for domestic wastewater

Biodegradation of settled COD is studied by evaluating the associated OUR profile obtained in an aerated batch reactor. Hydrolysis was selected, as in current modelling, as the rate-limiting step for O2 consumption. Settled COD was found to incorporate a significant fraction of active biomass that needs to be accounted for in the evaluation. The analysis of the OUR profile yielded a significantly slower hydrolysis mechanism for settled COD, compared to its soluble slowly biodegradable counterpart. WaterSA Vol.28(3) 2002: 299-30

Respirometric evaluation and modelling of acetate utilization in sequencing batch reactor under pulse and continuous feeding

The study investigated the effect of feeding regime and sludge age on acetate utilization. Parallel sequencing batch reactors (SBRs) were operated at steady-state with pulse and continuous feeding of acetate at sludge ages of 8 and 2 days. Acetate was always partially converted to poly-beta-hydroxybutyrate (PHB). The adopted model remained equally applicable to oxygen uptake rate and PHB profiles reflecting different feeding regimes and culture history. Sludge age was significant on the rate parameters of storage and direct growth (k(STO), mu(H1)). while the feeding regime affected half saturation coefficients (K-STO, K-S1). Changing the sludge age from 8 days to 2 days reduced the K-STO value from 8.0 day(-1) to 6.5 day(-1) and increased the corresponding mu(H1) value from 1.5 day(-1) to 2.5 day(-1), regardless of the feeding regime; conversely, changing from pulse to continuous feeding reduced K-STO while increasing K-S for the SBR operation at the same sludge age. (C) 2011 Elsevier Ltd. All rights reserved

Pollutant footprint analysis for wastewater management in textile dye houses processing different fabrics

BACKGROUND: This study investigated the water and pollution footprints of a dye house, which processed cotton knits, polyester (PES) knits and PES-viscose woven fabrics. Experimental evaluation was carried out for each processing sequence. Variations in wastewater flow and quality were established as a function of the production program in the plant. A model evaluation of wastewater dynamics was performed and defined specifications of an appropriate treatment scheme. RESULTS: The plant was operated with a capacity of 4300 t year−1 of fabric, which generated a wastewater flow of 403 500m3 year−1 and a COD load of 675 t year−1. The overall wastewater footprint of the plant was computed as 91m3 t−1 and the COD footprint as 160 kg t−1 of fabric. Depending on the fabric type, results indicated expected changes in wastewater flow between 600 and 1750m3 day−1 in COD load between 1470 and 2260 kg day−1 and in COD concentration between 1290 and 3400mgL−1. CONCLUSION: A model simulation structured upon COD fractionation and related process kinetics revealed partial removal of slowly biodegradable COD, coupled with high residual COD, which would by-pass treatment. Resulting biodegradation characteristics necessitated an extended aeration system, which could also enable partial breakdown of residual COD. Effluent COD could be reduced to 220–320mgL−1 with this wastewater management strategy. © 2018 Society of Chemical Industr