Propane Dehydrogenation Wastewater Treatment using Sequencing Batch Reactors

The purpose of this study was to determine the effectiveness of using a
Sequencing Batch Reactor (SBR) in treating PDH wastewater, to determine the effect of
various organic loading rates on SBR performance and lastly, to determine the optimum
operating conditions for the SBR. Industrial wastewaters commonly contain high organic
loads as well as toxic and inhibitory substance such as sulphide. Therefore, the
conventional activated sludge process is inefficient in treating wastewater of this nature.
The wastewater sample was collected from a Propane Dehydrogenation (PDH) plant in
Kuantan, Pahang. The initial wastewater characteristics of the sample before treatment
were determined. Biomass obtained from the Sewage Treatment Plant (STP) at Universiti
Teknologi Petronas (UTP), which was cultured for three months in a reactor in the
Environmental laboratory, was used to inoculate the wastewater in the SBR. The
performance of the SBR in treating the PDH wastewater was investigated with a
suspended biomass configuration and operating under the following sequence: fill, react,
settle and decant. The effects of four different organic loading rates were investigated.
Two sequencing batch reactors were operated simultaneously, each initially having a total
cycle period of 24 hours and respective organic loading rates of 0.7 kgCOD/m3/day and
1.5 kg COD/m3/day, which were respectively reduced to 0.35 kgCOD/m3/day and 0.183
kgCOD/m3/day after 30 days of operation. The performance of the SBR was assessed by
measuring the COD, BOD and sulphide concentrations after each cycle, among other
parameters. It was determined that the optimum operating conditions for the SBR were a
0.35 kgCOD/m3/day organic loading rate with a subsequent HRT of 20 days and a 24
hour cycle period, where the COD, BOD and sulphide removal efficiencies of up to
96%, 98% and 97% respectively were achieved. Results showed that a high organic
loading rate inhibited the SBR performance. The sulphide concentration was sufficiently
reduced to meet the Environmental Quality (sewage & industrial effluent) Regulations,
1979 under the 3`d schedule Environmental Quality Act, 1974, where the sulphide limit is
0.5 mg/L for both standard A and B.