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Low condition of dissolved oxygen (DO) is commonly associated with sludge bulking problem that was able to disrupt the efficiency of wastewater treatment performances. Relatively, very little attention was paid to the possibility of applying magnetic field in controlling the bulking problem. Hence, this study aims to investigate the performance of magnetic field on biomass properties and its effect on biodegradation under low condition of DO. Two continuous laboratory-scale sequencing batch reactors—Reactor A (SBRA) and Reactor B (SBRB)—were setup. SBRA was equipped with the magnetic device to exhibit magnetic field of 88 mT, while SBRB acted as a control system. The results showed that the biomass concentration in SBRA was higher compared to SBRB. High biomass concentration in SBRA resulted to better settleability with mean SVI of less than 30 mL/g. SBRA also showed consistently high removal performances of organic and inorganic contents compared to SBRB. These observations confirmed that the magnetic field was able to enhance the biomass properties, which further enhance the biodegradation ability of the aerobic bacteria under low DO condition. This also indicates that under the sludge bulking circumstances, the use of magnetic field stands a great chance in maintaining high biodegradation of the treatment system.

Air pollution is a worldwide issue that is mainly caused from excessive inhalation of hazardous PM2.5 pollutant that is emitted into the air. The objective of this study is to assess the fundamental knowledge revolving PM2.5 (particles aerodynamic diameter of lower than or equal to 2.5 μm) and its inorganic composition in ambient air of urban areas, mainly in Malaysia in comparison to other Southeast Asia countries. This research also investigates the theory of particle number concentration (PNC) with PM2.5, also the health effects and origins of the emissions. The factors affecting the PM2.5 mass include the local emission, El Nino phenomenon, land, meteorological effects, monsoons, rainfall events, sea breeze, transboundary pollution and seasonal changes. 24 h mean PM2.5 mass concentration for metropolitan regions in the SEA is in the range of 11 μgm−3 and 72.3 μgm−3, while between 5.30 μgm−3 and 55.89 μgm−3 for semi-urban zones. For rural area, the 24 h mean PM2.5 value is about 30 μgm−3. The findings indicate that metals in PM2.5 emission are frequently Pb, Se, Zn, Cd, As, Bi, Ba, Cu, Rb, V, Ni, Fe, Ca, Mn, Cr, Al, Si and K, where Zn has the uppermost range of 133.50 to 419.30 ngm−3 while the major water-soluble ions exist are NH4+, K+, Ca2+, Na+, in which Na+, NH4+ and Cl- are present in aged sea salt and mixed industrial, Ca2+ and Mg2+ present in mineral dust, NH4+, K+ and SO42− present in mixture of SIA and biomass burning. There is a high correlation between the particle mass concentration and PNC level, especially the ones in accumulation mode (PNC0.1–1.0) which are mostly originated from the emission of heavy traffic streets.

The present work investigates the feasibility of aerobic granulation for the treatment of low-medium strength domestic wastewater for long-term operation and effects of a static mixer on the properties and removal performances of the aerobic granules formed. The static mixer was installed in a sequential batch reactor to provide higher hydrodynamic shear force in enhancing the formation of the aerobic granules. Aerobic granules were successfully formed in the domestic wastewater, and the granulation treatment system was sustained for a period of 356 days without granules disintegration. Subsequent to the installation, aerobic granules with a low SVI30 of 41.37 mL/gTSS, average diameter 1.11 mm, granular strength with integrity coefficient 10.4% and regular shape with minimum filamentous outgrowth were formed. Mineral concentrations such as Fe, Mg, Ca and Na as well as composition of protein and polysaccharide in tightly bound-extracellular polymeric substance of the aerobic granules were found to be higher under the effect of the static mixer. However, no significant improvement was observed on the TCOD, NH4+-N and TSS removal performance. Good TCOD and TSS removal performance of above 85% and 90%, respectively and moderate NH4+-N removal performance of about 60% were observed throughout the study. Higher simultaneous nitrification and denitrification (SND) efficiency of 56% was observed after the installation of the static mixer, as compared to 21% prior. Therefore, it may be concluded that the installation of the static mixer significantly improved the properties of aerobic granules formation and SND efficiency but not the TCOD, NH4+-N and TSS removal performance.

Nutrients contribute to the wellbeing of water bodies. However, excessive enrichment of water bodies by nutrients could harm aquatic organisms. Some of the severe environmental problems caused by nutrients on water bodies include eutrophication and algal bloom. In children, consumption of nitrate-polluted water causes methaemoglobinemia. Consumption of food irrigated with nutrient-polluted wastewater has been associated with several health implications. These nutrients primarily originate from point and non-point sources. Several biological-suspended treatment systems have been developed to reduce nutrients to acceptable limits prior to discharge into water bodies. These treatment systems are associated with several merits and demerits. This chapter explores the implications of water body enrichment by nutrients and their impact on health, economy, and environment. Furthermore, some suspended growth treatment systems applied for the treatment of nutrient polluted wastewater were explored.

Electrocoagulation has emerged a reliable technology for the treatment of various wastewaters. Its basic principle depends on the response of water particles to strong electric field in a redox reaction. Oxidation of the anode material releases coagulating agents that form metal hydroxide complexes which neutralize particulate materials to form agglomerates. The agglomerates either settle at the bottom or float to the surface depending on the removal path of the electrocoagulation reactor. The merits of electrocoagulation include minimal sludge generation, minimal operator attention, simple equipment, high pollutant removal capacity, and ease of operation. Therefore, this chapter explores the mechanisms of electrocoagulation, components of electrocoagulation, benefits, and demerits of electrocoagulation. Furthermore, the similarity between electrocoagulation and coagulation is explored. Application of electrocoagulation for the treatment of various wastewaters was explored. Feasibility of electrocoagulation was examined through cost evaluation with other treatment technologies.

Understanding of mass transfer kinetics is important for biosorption of nitrogen compounds from palm oil mill effluent (POME) to gain a mechanistic insight into future biological processes for the treatment of high organic loading wastewater. In this study, the rates of global and sequential mass transfer were determined using the modified mass transfer factor equations for the experiments to remove nitrogen by aerobic granular sludge accumulation in a sequencing batch reactor (SBR). The maximum efficiencies as high as 97% for the experiment run at [kLa]g value of 1421.8 h−1 and 96% for the experiment run at [kLa]g value of 9.6 × 1037 h−1 were verified before and after the addition of Serratia marcescens SA30, respectively. The resistance of mass transfer could be dependent on external mass transfer that controls the transport of nitrogen molecule along the experimental period of 256 days. The increase in [kLa]g value leading to increased performance of the SBR was verified to contribute to the fu...

Over the decades the palm oil industry has managed some challen ging environmental concerns regarding land transformation and degradation, increas e in eutrophication, changing habitats of wildlife, pesticides runoff into inland wa tercourses, and probable climate change. Countries producing palm oil desire to do so in a more sustainable way that will leave the environment evergreen. Therefore this paper aims to encourage sustainable management of agro-industrial waste and its potenti al in making financial returns from the same waste. Hence, the study was conducted with the participation of seven local palm oil mills having different capacities and oper ation age. Attention was given to milling waste as they could cause serious environmenta l menace if unattended to properly. Milling waste includ es lignocellulosic palm biomas s namely the empty fruit bunches (EFB), oil palm shell (OPS), mesocarp fibres, pal m oil mill effluent (POME), and palm oil mill sludge (POMS), as well as solid waste generated from the further processing of these biomass into the palm oil fuel ashe s (POFA) and palm oil clinkers (POC). The opportunities available to the Malaysian pa lm oil industry and the financial benefits which may accr ue from waste generated during palm oil production process cannot be over emphasized.

Kinetic and mass transfer aspects of biosorption of oxidisable organic matter (OOM) from wastewater are important for better understanding of the mechanisms of granules initiation and development. The modified mass transfer factor models were used to predict the liquid–solid mass transfer rates of OOM biosorption from palm oil mill effluent (POME) attached to aerobic granular sludge (AGS) in a sequencing batch reactor (SBR). The variations of [kLa]g, [kLa]f and [kLa]d pursuant to time were verified to have a zigzag pattern due to the organic loading rate varies with a change in the quality of POME feeding the SBR. The influence of added Serratia marcescens SA30 on the rates of mass transfer would be very remarkable due to the effects of metabolites and biomass growth this can lead to a rapid utilisation of OOM accumulated into AGS. The maximum efficiencies of SBR reaching 48% for CODt removal at [kLa]g value of 3.054 h−1 and 68% for CODs removal at [kLa]g value of 21.012 h−1 were verified before the addition of S. marcescens SA30 and those reaching 68% for CODt removal at [kLa]g value of 1.229 × 1063 h−1 and 94% for CODs removal at [kLa]g value of 7.152 × 1064 h−1 were verified after the addition of S. marcescens SA30. The resistance of mass transfer could be dependent on external mass transfer, which controls the movement of organic molecules along the experimental period of POME fed the SBR without and with added S. marcescens SA30. The performance of SBR would increase with increase of [kLa]g value, and this provides new insight into dynamic response of the aerobic digestion to AGS development.

Biogranulation is an effective biological technology suitable for the treatment of various wastewaters. However, the major drawback of this technique is the long start-up period for biogranule development. Hence, the primary focus of this study was on cell surface hydrophobicity which is the main parameter that indicates cell agglomeration during the initial self-immobilization process of aerobic granulation. The effects of sludge concentration and magnetic activated carbon on cell surface hydrophobicity were investigated in this study. Response surface methodology (RSM) was applied to design, analyze, and optimize the outcome of the study. Experiments were performed at sludge concentration of 1,000-3,000 mg/L and magnetic activated carbon mass of 1-5 g/L with 24 hr of aeration time. The results show that both variables yielded a positive significant effect on the initial development of aerobic granulation with 56% surface hydrophobicity. Interaction effects between variables on the responses were significant with positive estimated interaction effect at all different measured aeration time. The magnetic activated carbon acted as nuclei to induce bacterial attachment and further enhanced the initial process of biogranule development under optimal condition of 1:1.1 (sludge concentration: magnetic activated carbon). PRACTITIONER POINTS: Cell surface hydrophobicity was evaluated Magnetic activated carbon enhanced cell surface hydrophobicity Response surface methodology was employed for analyses Magnetic activate carbon mass and biomass concentration was significant Magnetic activated carbon acted as nuclei to improve biogranulation.

Sludge bulking caused by filamentous microorganisms is one of the prevailing operational problems in activated sludge process. Its severity is determined by the relative abundance of filame...

Aerobic granulation is a promising technology that has increasingly attracted global attention due to its potential as a cost effective system, and its application in a wide range of wastewaters. Aerobic granules are highly structured suspended microbial aggregates capable of degrading biodegradable compounds with excellent settling properties, good pollutant removal and high resistance to toxic compounds. However, evidences show that granules formation in high strength wastewaters takes relatively much longer time at initial stages. This article reviews the state-of-the-art of the researches done on the factors influencing granulation at initial stage, with particular focus on the aggregation of microbial cells. In addition, this review discusses the effective approaches adopted for the enhancement of initial development of aerobic granules. Moreover, the current article highlights the mechanism of aerobic granulation at its initial stage, as well as other different approaches. Finally, future research directions to improve aerobic granules formation at the initial stage are discussed.

This study investigated the effect of various cations (Ca2+, Mg2+, Al3+, Mn2+, Zn2+) on the autoaggregation (AAg) and surface hydrophobicity (SHb) of three different bacteria (Brevibacillus panacihumi strain (ZB1), Lysinibacillus fusiformis strain (ZB2) and Enterococcus faecalis strain (ZL)) using a 2-level factorial design. The AAg ratio was measured from the changes in the absorbance of the media. Results show that ZB2 had maximum AAg for the three bacteria investigated. A microscopic clustering of cells was observed when Ca2+ was added to ZB2. The AAg was in the range of 62%, 58% and 34% for ZB2, ZB1 and ZL, respectively and correlated to the SHb. The aggregation and SHb of the microbial cells increased with increasing ionic strength due to the repulsive steric or overlap forces between the polymer covered surfaces. Ca2+ demonstrated a more significant effect on aggregation and SHb of microbial cells due to an attractive binding force.

This study evaluated the performance of aluminum and iron plate electrode systems on the continuous electrocoagulation of boron from produced water under varying conditions of retention time, initial concentration and electrode distance. The experimental data were validated for mass transfer resistance using the modified mass transfer factor (MMTF) model. Results show a similar trend for both electrode systems. Boron removal decreased from 78.7–60% for aluminum electrode and 67.3–53.3% for iron electrode with shortening retention time from 45 to 30 min.. Boron removal further decreased from 84 to 72.7 % for aluminum electrode and 76 to 61.3 % for iron electrode with increasing electrode distance from 0.5 cm to 1.5 cm. Analyses of the mass transfer resistance showed that the driving force (B) for boron mass transfer was concentration dependent and increased from 0.1037 to 0.4002 mg.g for aluminum electrode and 0.0445 to 0.1258 mg.g for iron electrode with increasing initial boron concentration from 5 to 15 mg/L. A similar trend was observed for the affinity between boron and the electroactive species. Analyses of boron mass transfer resistance related to the global and film mass transfer, and porous diffusion show that boron mass transfer resistance correlated to the film mass transfer for both electrode systems. Aluminum electrode system showed better performance for boron removal and higher mass transfer kinetics. This study clearly demonstrates that continuous electrocoagulation is a suitable alternative for boron removal from produced water.

This study examined the degradation of pesticide aqueous solution containing chlorpyrifos, cypermethrin and chlorothalonil by the FeGAC/H2O2 process. Under the operating conditions (FeGAC 5 g/L, H2O2 concentration 100 mg/L and pH 3), chemical oxygen demand (COD) and total organic carbon removal were 96.2 and 79.2%, respectively, and biodegradability (BOD5/COD ratio) increased from 0 to 0.40 after 60 min reaction. Complete degradation of chlorpyrifos, cypermethrin and chlorothalonil pesticides active ingredients occurred in 1 min. Kinetic models such as pseudo-first-order, pseudo-second-order and intraparticle diffusion were evaluated. The Fourier transform infrared spectra (treated and untreated pesticide aqueous solutions) also indicated modification and/or degradation of the pesticide organic bonds. The study showed that FeGAC/H2O2 process can be used for the pretreatment of pesticide aqueous solution containing chlorpyrifos, cypermethrin and chlorothalonil before further treatment by biological...

The fundamental understanding of mass transfer kinetics is essential for biosorption of phosphorus by aerobic granular sludge (AGS) to gain an insight into biological processes regarding the treatment of wastewater with high organic load. The removal of phosphorus by AGS from palm oil mill effluent was performed in a sequencing batch reactor (SBR) while the experimental data were assessed using the modified mass transfer factor (MMTF) models to get better understanding on the mechanisms of external and internal mass transfer. A zigzag pattern of the [kLa]g, [kLa]f and [kLa]d variations was verified before and after addition of Serratia marcescens SA30 due to the variations of organic loading rate and total phosphorus concentration were observed at every additional 50% new sample into the SBR. This study verified that the biosorption process is controlled by transport of phosphorus through a film of external fitting AGS. The analysis of SBR performance shows a logarithmic increase in the efficiency of phosphorus removal with increasing of the [kLa]g value. A new insight of the dynamic AGS growth of biological process revealed by the MMTF models may contribute to the advanced treatment of high organic content wastewater.

An integrated hybrid bioreactor (IHB) and integrated suspended bioreactor (ISB) coupling aerobic, anoxic and settling units was evaluated for industrial wastewater treatment with and without the installation of a rectangular hollow engraved submerged Perspex media in the aerobic unit. Bioreactor performance was examined at different overall hydraulic retention times of 36, 12, 7.2, 5.1 and 4 days, respectively. Nitrogen mass balance was analyzed to examine the inhibitory effects of metabolic by-products on nitrification in IHB. Both bioreactors exhibited a short start-up period during acclimatization. Results show a lower effluent COD concentration of 15–85 mg/L in IHB and 38.6–124 mg/L in ISB. Effluent ammonia-nitrogen was 0.65–3.5 mg/L in IHB and 0.3–4.5 mg/L in ISB. Effluent nitrate and nitrite were low in both bioreactors but lower in IHB. Mass balance analysis in IHB indicated that nitrate was the dominant ammonia metabolite and decreased with reducing HRT. Microfauna investigation showed that free swimmers, crawling and attached ciliates were major protozoans in IHB while free swimmers and attached ciliates were dominant protozoans in ISB. Kinetic evaluation demonstrates that microbial growth was higher in IHB. The Y, kd, μmax and Ks for IHB was 0.1 g VSS/g COD, 0.02 per day, 0.81 per day and 1.26 g/m3 with a correlation coefficient (R2) of 0.978 while it was 0.118 g VSS/g COD, 0.04 per day, 0.635 per day and 3.93 g/m3 with a correlation coefficient (R2) of 0.988 in ISB. This study demonstrates that while both ISB and IHB were effective for industrial wastewater treatment, IHB performance was comparatively higher due to the inclusion of the submerged media.

The developed microbial granules containing photosynthetic pigments had successfully achieved approximately 18–21% of carbon dioxide (CO2) removal in POME for one complete SBR cycle. Also, the granules had reached CO2 removal at 15–29% within 24 h and removal of 25% after 5 days. Both results were inconsistent possibly due to the slow mass transfer rate of CO2 from gas to liquid as well as the simultaneous effect of CO2 production and respiration among the microbes. Furthermore, results showed the removal of CO2 from air increases proportionally with the CO2 removed in liquid. The CO2 biofixation of granules attained was approximately 0.23 g/L/day for a week. Using the regression model, the removal of CO2 between liquid and gas, CO2 biofixation rate were highly correlated with the treatment time. A statistically significant relationship was obtained between CO2 concentration in liquid, biomass productivity and treatment time for the CO2 biofixation rate of the granules.

The combination of granular activated carbon (GAC)–hydrogen peroxide (FeGAC/H2O2) (pretreatment phase) and sequencing batch reactor (SBR) (post-treatment phase) for the removal of biochemical oxygen demand, chemical oxygen demand and improvement of the biodegradability of the pesticide wastewater was studied. In the pretreatment phase, COD and TOC removal were 64.2 and 50.5 %, respectively, and biodegradability (BOD5/COD ratio) increased from 0.02 to 0.34. During the SBR, initial treatment of the pretreated wastewater without addition of municipal wastewater was not sustained. The pretreatment time was further increased before combining the wastewater with municipal treatment plant wastewater for an effective treatment. The FeGAC/H2O2-SBR reached 97.1, 98.0 and 99.9 % for COD, TOC and BOD5 removal, respectively. The FeGAC/H2O2-SBR process can be applied for the treatment of pesticide wastewater to meet the Malaysian regulatory effluent discharge standard.

In activated sludge system, the performance of the process largely depends on the balance between filamentous and floc-forming microorganisms. When the normal balance of these biological communities is disturbed, filamentous microorganisms tend to proliferate, causing various problems to the treatment performances such as sludge bulking. Various approaches have been used to control the proliferation of filamentous microorganisms. However, the approaches led to various drawbacks that eventually worsen the performances of treatment systems. Therefore, this study is aimed to investigate the potential approach using static magnetic field in inhibiting filamentous microorganisms that presence in the sludge bulking. Magnetic field of intensity 88 mT was used. Its exposure on the filamentous microorganisms was investigated in terms of filaments' characteristics such as branching, shape and filaments' location. The analysis indicated that the magnetically exposed activated sludge showed less possibility presence of the filamentous microorganisms compared to unexposed activated sludge.

Natural coagulants have been increasingly popular in the past few years due to its benefits and the fact that it resolves most of the associated problems when using chemical coagulants. Plant-based natural coagulants perform coagulation either by polymer bridging or charge neutralization, it can be extracted from various plant components. Concerted research and development efforts have been conducted in discovering new plant species and constituents that can be used as natural coagulants, which further boosting the effectiveness of existing plant-based natural coagulants. The objective of this paper is to provide a mini review on studies done over the span of ten years regarding plant-based natural coagulants. This paper also includes advantages and disadvantages of natural coagulants prior to identify several potential research gaps to provide platform towards the need of further study.