Kinetics and performance study of ultrasonic-assisted membrane anaerobic system using Monod Model for Palm Oil Mill Effluent (POME) treatment Ayub Md Som * , Asdarina Yahya Faculty of Chemical Engineering, Universiti Teknologi MARA, 40450, Shah Alam, Selangor, Malaysia ARTICLE INFO Keywords: Ultrasonic-assisted membrane anaerobic system Membrane fouling control COD removal Efficiency Methane production Monod model ABSTRACT The discharge of Palm Oil Mill Effluent (POME) to river or sewage has caused serious environmental problems for the past several decades. This has prompted many researchers to find alternative technologies such as the use of an ultrasonic-assisted membrane anaerobic system, also known as UMAS. However, further use of UMAS in treating POME tends to create blockage on the membrane surface, which is commonly known as membrane fouling. In this study, kinetic parameters of POME samples which contributed to the fouling were investigated, namely; the biomass growth rate, μ max and substrate utilization rate, K s . Two different sources of POME samples were taken from namely; a final discharge pond at Felda Sungai Tengi, Selangor and decanter processing units at Felda Jengka, Pahang. The POME samples were treated by UMAS in a 26-Litre laboratory reactor which operated 5 h per day for a HRT of 7 days so as to observe their performance in terms of percentage COD removal and CH 4 production. Performance results revealed that maximum COD removal efficiencies were 82.75% and 94.43% for the final discharge pond and decanter processing unit samples respectively. All these data were collected and curve fitting methods were then used to construct appropriate profiles for μ max and K s following a Monod model. It was found that the high OLR sample (decanter) apparently yielded better efficiency of POME treatment (i.e. calculated μ max of 0.327 day 1 ,K s of 0.361 g COD/g VSS. d, and volume of CH 4 gas produced at 25 m 3 ) compared to that of low OLR sample from ponds (i.e. calculated μ max of 0.237 day 1 ,K s of 0.1674 g COD/VSS. d, and volume of CH 4 gas produced at 9 m 3 ). In conclusion, it shows that UMAS is a promising treatment to treat POME in which its calculated kinetic coefficients of μ max and K s are similar to the theoretical values when Monod Model is employed in this study. 1. Introduction Palm oil industry has continuously played an important role towards Malaysian economic growth. The products derived from palm oils are highly used in everyday life, 80% of which are for food applications; for example, oil-based food products namely; margarine, shortening, cook- ing and frying oils, vegetable ghee, chocolate, and as replacement for milk fat for the production of non-dairy creamers or whiteners. For non- food applications, these products are used in detergents, cosmetics, biodiesel and energy generation (Cheng, 2010). Malaysia is currently the world’s largest exporter of palm oil, even though it is the world’s second largest producer of palm oil after neigh- bouring Indonesia, which occupies world export shares of 37.9% and 53.4%, respectively (Petchseechoung, 2016). Oil palm plantations covered only 16 percent of overall total agricultural area in Malaysia, which is equivalent to about 5.23 million hectares in 2014 compared to 3.79 million hectares in 2003. In 2014, there were in total 429 palm oil mills throughout Malaysia processing 95.4 million tonnes of fresh fruit bunches and producing 19.65 million tonnes of crude palm oil (CPO) (Liew et al., 2016). This CPO production was worth approximately RM 44.3 billion of sales. Nevertheless, development of the oil palm industry has contributed to environmental pollution due to huge generation of by-products associ- ated with its oil extraction processes. The processing of palm oil produces more than 70% by weight of processed FFB which has come out as oil palm waste. According to Yacob et al. (2005), about 26.7 million tonnes of solid biomass and 30 million tonnes of POME were generated from 381 palm oil mills in Malaysia. In 2004 a total of 381 mills were recorded and the number increased to 429 mills in 2014. Thus, after ten years, palm oil plantation area had increased by 11.2% in Malaysia. Every year shows an increase in demand for palm oil products. Hence, this results in an expansion of POME discharge from this industry. The * Corresponding author. E-mail address: ayub522@uitm.edu.my (A.M. Som). Contents lists available at ScienceDirect Cleaner Engineering and Technology journal homepage: www.journals.elsevier.com/cleaner-engineering-and-technology https://doi.org/10.1016/j.clet.2021.100075 Received 11 September 2020; Received in revised form 19 February 2021; Accepted 19 March 2021 2666-7908/© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/). Cleaner Engineering and Technology 2 (2021) 100075