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A sequential treatment of intermediate tropical landfill leachate using a sequencing batch reactor (SBR) and coagulation

Yong ZJ, Bashir MJK, Ng CA, Sethupathi S, Lim JW

J Environ Manage, 2018 Jan 01;205:244-252.
PMID: 28987987 DOI: 10.1016/j.jenvman.2017.09.068

The increase in landfill leachate generation is due to the increase of municipal solid waste (MSW) as global development continues. Landfill leachate has constantly been the most challenging issue in MSW management as it contains high amount of organic and inorganic compounds that might cause pollution to water resources. Biologically treated landfill leachate often fails to fulfill the regulatory discharge standards. Thus, to prevent environmental pollution, many landfill leachate treatment plants involve multiple stages treatment process. The Papan Landfill in Perak, Malaysia currently has no proper leachate treatment system. In the current study, sequential treatment via sequencing batch reactor (SBR) followed by coagulation was used to treat chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N), total suspended solids (TSS), and colour from raw landfill leachate. SBR optimum aeration rate, L/min, optimal pH and dosage (g/L) of Alum for coagulation as a post-treatment were determined. The two-step sequential treatment by SBR followed by coagulation (Alum) achieved a removal efficiency of 84.89%, 94.25%, 91.82% and 85.81% for COD, NH3-N, TSS and colour, respectively. Moreover, the two-stage treatment process achieved 95.0% 95.0%, 95.3%, 100.0%, 87.2%, 62.9%, 50.0%, 41.3%, 41.2, 34.8, and 22.9 removals of Cadmium, Lead, Copper, Selenium, Barium, Iron, Silver, Nickel, Zinc, Arsenic, and Manganese, respectively.
Treatment of palm oil mill effluent using combination system of microbial fuel cell and anaerobic membrane bioreactor

Tan SP, Kong HF, Bashir MJK, Lo PK, Ho CD, Ng CA

Bioresour Technol, 2017 Dec;245(Pt A):916-924.
PMID: 28931208 DOI: 10.1016/j.biortech.2017.08.202

It was found that the operational temperature and the incorporation of microbial fuel cell (MFC) into anaerobic membrane bioreactor (AnMBR) have significant effect on AnMBRs' filtration performance. This paper addresses two issues (i) effect of temperature on AnMBR; and (ii) effect of MFC on AnMBRs' performance. The highest COD removal efficiency was observed in mesophilic condition (45°C). It was observed that the bioreactors operated at 45°C had the highest filtration resistance compared to others, albeit the excellent performance in removing the organic pollutant. Next, MFC was combined with AnMBR where the MFC acted as a pre-treatment unit prior to AnMBR and it was fed directly with palm oil mill effluent (POME). The supernatant from MFC was further treated by AnMBR. Noticeable improvement in filtration performance was observed in the combined system. Decrease in polysaccharide amount was observed in combined system which in turn suggested that the better filtration performance.
Calculation of energy recovery and greenhouse gas emission reduction from palm oil mill effluent treatment by an anaerobic granular-sludge process

Show KY, Ng CA, Faiza AR, Wong LP, Wong LY

Water Sci Technol, 2011;64(12):2439-44.
PMID: 22170839 DOI: 10.2166/wst.2011.824

Conventional aerobic and low-rate anaerobic processes such as pond and open-tank systems have been widely used in wastewater treatment. In order to improve treatment efficacy and to avoid greenhouse gas emissions, conventional treatment can be upgraded to a high performance anaerobic granular-sludge system. The anaerobic granular-sludge systems are designed to capture the biogas produced, rendering a potential for claims of carbon credits under the Kyoto Protocol for reducing emissions of greenhouse gases. Certified Emission Reductions (CERs) would be issued, which can be exchanged between businesses or bought and sold in international markets at the prevailing market prices. As the advanced anaerobic granular systems are capable of handling high organic loadings concomitant with high strength wastewater and short hydraulic retention time, they render more carbon credits than other conventional anaerobic systems. In addition to efficient waste degradation, the carbon credits can be used to generate revenue and to finance the project. This paper presents a scenario on emission avoidance based on a methane recovery and utilization project. An example analysis on emission reduction and an overview of the global emission market are also outlined.
Fulltext Adsorptive Removal of Iron Using SiO2 Nanoparticles Extracted from Rice Husk Ash

Nguyen TT, Ma HT, Avti P, Bashir MJK, Ng CA, Wong LY, et al.

J Anal Methods Chem, 2019;2019:6210240.
PMID: 31275692 DOI: 10.1155/2019/6210240

In this work, SiO2 nanoparticles were prepared by the sol-gel method after sodium silicate was extracted from rice husk ash (RHA) under various experimental conditions such as types of acids, NaOH concentration, dissolved time, and temperature and used for removal of Fe2+ ions from aqueous solutions. The extracted SiO2 was morphologically and chemically characterized and showed a surface area of 78 m2/g and uniform pores of 2.71 nm, offering high adsorption capacity for Fe2+ ions. The influence of pH, contact time, and amount of adsorbent was studied in order to establish the best conditions for the Fe2+ adsorption and removal. Furthermore, the adsorption data were fitted with an exponential shape curve for all the three variable parameters that affect the adsorption process. The best results were obtained for pH 5, 20 min contact time, and 0.5 g adsorbent dose. The loading adsorption capacity was 9 mg of Fe2+ ions/g SiO2 in the concentration range 0.1-1.0 mgL-1. In addition, the synthesized SiO2 with the size of around 50 nm can be used for specific heavy metal removal and drug delivery, after modification of the SiO2 surface with various functional groups.
Optimization of membrane bioreactors by the addition of powdered activated carbon

Ng CA, Sun D, Bashir MJ, Wai SH, Wong LY, Nisar H, et al.

Bioresour Technol, 2013 Jun;138:38-47.
PMID: 23612160 DOI: 10.1016/j.biortech.2013.03.129

It was found that with replenishment, powdered activated carbon (PAC) in the membrane bioreactor (MBR) would develop biologically activated carbon (BAC) which could enhance filtration performance of a conventional MBR. This paper addresses two issues (i) effect of PAC size on MBR (BAC) performance; and (ii) effect of sludge retention time (SRT) on the MBR performance with and without PAC. To interpret the trends, particle/floc size, concentration of mixed liquor suspended solid (MLSS), total organic carbon (TOC), short-term filtration properties and transmembrane pressure (TMP) versus time are measured. The results showed improved fouling control with fine, rather than coarse, PAC provided the flux did not exceed the deposition flux for the fine PAC. Without PAC, the longer SRT operation gave lower fouling at modest fluxes. With PAC addition, the shorter SRT gave better fouling control, possibly due to greater replenishment of the fresh PAC.
Fulltext The effect of rooming-in on duration of breastfeeding: A systematic review of randomised and non-randomised prospective controlled studies

Ng CA, Ho JJ, Lee ZH

PLoS One, 2019;14(4):e0215869.
PMID: 31022227 DOI: 10.1371/journal.pone.0215869

BACKGROUND: The benefits of six months exclusive breastfeeding are well established for both mother and infant. One of the 10 steps of the Baby Friendly Hospital Initiative is rooming-in (mother and baby together in the same room throughout hospitalisation). A Cochrane review found only one randomised controlled trial (RCT) examining the effects of continuous rooming-in versus nursery care on breastfeeding duration, and concluded there was insufficient evidence to support or refute either practice. We aimed to examine the effect of continuous or intermittent rooming-in on breastfeeding duration.
METHODS AND FINDINGS: We included all prospective controlled studies (randomised and non-randomised) comparing rooming-in to nursery care that reported full or partial breastfeeding up to six months. We used the 2016 search results of the Cochrane review and updated the search to August 2018 using OVID MEDLINE. Duplicate data extraction and assessment of risk of bias were performed. Meta-analyses were performed using REVMAN 5. The GRADE approach was used to assess quality of evidence. Seven studies were included, five had 24-hour-per-day, one daytime only and one 8-hours-per-day rooming-in. Four studies had at least one additional co-intervention: Differences in delivery room management, and educational packages. All studies contributing to meta-analyses had 24-hour rooming-in. There was no difference in the proportion of infants on full breastfeeding at 3 months (RR 1.14; 95% CI 0.84 to 1.54; very-low-quality evidence), 4 months (RR 0.99; 95% CI 0.73 to 1.33; very-low-quality evidence) and 6 months (RR 0.95; 95% CI 0.57 to 1.58; low-quality evidence). The proportion of infants on partial breastfeeding at 3-4 months was higher with rooming-in (RR 1.31; 95% CI 1.06 to 1.61; very-low-quality evidence).
CONCLUSION: The addition of non-randomised prospective controlled studies to existing evidence did not add further information on the effects of rooming-in on breastfeeding duration but resulted in lower quality of evidence. Uncertainty about the effects of rooming-in on breastfeeding duration remains.
Investigation on the performance of hybrid anaerobic membrane bioreactors for fouling control and biogas production in palm oil mill effluent treatment

Ng CA, Wong LY, Chai HY, Bashir MJK, Ho CD, Nisar H, et al.

Water Sci Technol, 2017 Sep;76(5-6):1389-1398.
PMID: 28953465 DOI: 10.2166/wst.2017.326

Three different sizes of powdered activated carbon (PAC) were added in hybrid anaerobic membrane bioreactors (AnMBRs) and their performance was compared with a conventional AnMBR without PAC in treating palm oil mill effluent. Their working volume was 1 L each. From the result, AnMBRs with PAC performed better than the AnMBR without PAC. It was also found that adding a relatively smaller size of PAC (approximately 100 μm) enhanced the chemical oxygen demand removal efficiency to 78.53 ± 0.66%, while the concentration of mixed liquor suspended solid and mixed liquor volatile suspended solid were 8,050 and 6,850 mg/L, respectively. The smaller size of PAC could also enhance the biofloc formation and biogas production. In addition, the smaller particle sizes of PAC incorporated into polyethersulfone membrane resulted in higher performance of membrane fouling control and produced better quality of effluent as compared to the membrane without the addition of PAC.
The short- and long-term inhibitory effects of Fe (II) on anaerobic ammonium oxidizing (anammox) process

Mak CY, Lin JG, Chen WH, Ng CA, Bashir MJK

Water Sci Technol, 2019 May;79(10):1860-1867.
PMID: 31294702 DOI: 10.2166/wst.2019.188

The application of the anammox process has great potential in treating nitrogen-rich wastewater. The presence of Fe (II) is expected to affect the growth and activity of anammox bacteria. Short-term (acute) and long-term effects (chronic) of Fe (II) on anammox activity were investigated. In the short-term study, results demonstrated that the optimum concentration of Fe (II) that could be added to anammox is 0.08 mM, at which specific anammox activity (SAA) improved by 60% compared to the control assay, 0.00 mM. The inhibition concentration, IC50, of Fe (II) was found to be 0.192 mM. Kinetics of anammox specific growth rate were estimated based on results of the batch test and evaluated with Han-Levenspiel's substrate inhibition kinetics model. The optimum concentration and IC50 of Fe (II) predicted by the Han-Levenspiel model was similar to the batch test, with values of 0.07 mM and 0.20 mM, respectively. The long-term effect of Fe (II) on the performance of a sequencing batch reactor (SBR) was evaluated. Results showed that an appropriate Fe (II) addition enhanced anammox activity, achieving 85% NH4+-N and 96% NO2--N removal efficiency when 0.08 mM of Fe (II) was added. Quantitative polymerase chain reaction (qPCR) was adopted to detect and identify the anammox bacteria.
Ancillary palm oil fuel ash (POFA) in sequencing batch reactor for enhancing recalcitrant pollutants removal from domestic wastewater

Lyn CW, Bashir MJ, Wong LY, Lim JW, Sethupathi S, Ng CA

Chemosphere, 2020 Nov 25.
PMID: 33276996 DOI: 10.1016/j.chemosphere.2020.129050

Domestic wastewater has been generated massively along with rapid growth of population and economic. Biological treatment using sequencing batch reactor (SBR) augmented with palm oil fuel ash (POFA) was investigated for the first time. The performance of POFA in enhancing biological treatment of wastewater has not been tested. The porosity property of POFA can improve SBR efficiency by promoting growth of mixed liquor suspended solids (MLSS) and formation of larger flocs for settling and facilitating attachment of microorganisms and pollutants onto POFA surfaces. The properties of POFA were tested to identify morphological properties, particle size, surface area, chemical compositions. Four SBRs, namely SBR1, SBR2, SBR3 and SBR4 were provided with aeration rate of 1, 2, 3 and 4 L/min, respectively. Each reactor was augmented with different dosages of POFA. Optimum aeration rate and POFA concentration were identified by the performance of SBRs in removing chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N) and colour from domestic wastewater. The results showed the most efficient COD (97.8%), NH3-N (99.4%) and colour (98.8%) removals were achieved at optimum POFA concentration of 4 g/L in SBR and aeration rate of 1 L/min. The study also found that higher aeration rate would contribute to the smaller specific size of flocs and decrease the pollutant removal efficiency.
Digital image processing and analysis for activated sludge wastewater treatment

Khan MB, Lee XY, Nisar H, Ng CA, Yeap KH, Malik AS

Adv Exp Med Biol, 2015;823:227-48.
PMID: 25381111 DOI: 10.1007/978-3-319-10984-8_13

Activated sludge system is generally used in wastewater treatment plants for processing domestic influent. Conventionally the activated sludge wastewater treatment is monitored by measuring physico-chemical parameters like total suspended solids (TSSol), sludge volume index (SVI) and chemical oxygen demand (COD) etc. For the measurement, tests are conducted in the laboratory, which take many hours to give the final measurement. Digital image processing and analysis offers a better alternative not only to monitor and characterize the current state of activated sludge but also to predict the future state. The characterization by image processing and analysis is done by correlating the time evolution of parameters extracted by image analysis of floc and filaments with the physico-chemical parameters. This chapter briefly reviews the activated sludge wastewater treatment; and, procedures of image acquisition, preprocessing, segmentation and analysis in the specific context of activated sludge wastewater treatment. In the latter part additional procedures like z-stacking, image stitching are introduced for wastewater image preprocessing, which are not previously used in the context of activated sludge. Different preprocessing and segmentation techniques are proposed, along with the survey of imaging procedures reported in the literature. Finally the image analysis based morphological parameters and correlation of the parameters with regard to monitoring and prediction of activated sludge are discussed. Hence it is observed that image analysis can play a very useful role in the monitoring of activated sludge wastewater treatment plants.
Generalized classification modeling of activated sludge process based on microscopic image analysis

Khan MB, Nisar H, Ng CA, Lo PK, Yap VV

Environ Technol, 2018 Jan;39(1):24-34.
PMID: 28278778 DOI: 10.1080/09593330.2017.1293166

The state of activated sludge wastewater treatment process (AS WWTP) is conventionally identified by physico-chemical measurements which are costly, time-consuming and have associated environmental hazards. Image processing and analysis-based linear regression modeling has been used to monitor the AS WWTP. But it is plant- and state-specific in the sense that it cannot be generalized to multiple plants and states. Generalized classification modeling for state identification is the main objective of this work. By generalized classification, we mean that the identification model does not require any prior information about the state of the plant, and the resultant identification is valid for any plant in any state. In this paper, the generalized classification model for the AS process is proposed based on features extracted using morphological parameters of flocs. The images of the AS samples, collected from aeration tanks of nine plants, are acquired through bright-field microscopy. Feature-selection is performed in context of classification using sequential feature selection and least absolute shrinkage and selection operator. A support vector machine (SVM)-based state identification strategy was proposed with a new agreement solver module for imbalanced data of the states of AS plants. The classification results were compared with state-of-the-art multiclass SVMs (one-vs.-one and one-vs.-all), and ensemble classifiers using the performance metrics: accuracy, recall, specificity, precision, F measure and kappa coefficient (κ). The proposed strategy exhibits better results by identification of different states of different plants with accuracy 0.9423, and κ 0.6681 for the minority class data of bulking.
Segmentation Approach Towards Phase-Contrast Microscopic Images of Activated Sludge to Monitor the Wastewater Treatment

Khan MB, Nisar H, Ng CA, Yeap KH, Lai KC

Microsc Microanal, 2017 12;23(6):1130-1142.
PMID: 29212566 DOI: 10.1017/S1431927617012673

Image processing and analysis is an effective tool for monitoring and fault diagnosis of activated sludge (AS) wastewater treatment plants. The AS image comprise of flocs (microbial aggregates) and filamentous bacteria. In this paper, nine different approaches are proposed for image segmentation of phase-contrast microscopic (PCM) images of AS samples. The proposed strategies are assessed for their effectiveness from the perspective of microscopic artifacts associated with PCM. The first approach uses an algorithm that is based on the idea that different color space representation of images other than red-green-blue may have better contrast. The second uses an edge detection approach. The third strategy, employs a clustering algorithm for the segmentation and the fourth applies local adaptive thresholding. The fifth technique is based on texture-based segmentation and the sixth uses watershed algorithm. The seventh adopts a split-and-merge approach. The eighth employs Kittler's thresholding. Finally, the ninth uses a top-hat and bottom-hat filtering-based technique. The approaches are assessed, and analyzed critically with reference to the artifacts of PCM. Gold approximations of ground truth images are prepared to assess the segmentations. Overall, the edge detection-based approach exhibits the best results in terms of accuracy, and the texture-based algorithm in terms of false negative ratio. The respective scenarios are explained for suitability of edge detection and texture-based algorithms.

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