The development of effluent removal prediction is crucial in providing a planning tool necessary for the future development and the construction of a septic sludge treatment plant (SSTP), especially in the developing countries. In order to investigate the expected functionality of the required standard, the prediction of the effluent quality, namely biological oxygen demand, chemical oxygen demand and total suspended solid of an SSTP was modelled using an artificial intelligence approach. In this paper, we adopt the clonal selection algorithm (CSA) to set up a prediction model, with a well-established method - namely the least-square support vector machine (LS-SVM) as a baseline model. The test results of the case study showed that the prediction of the CSA-based SSTP model worked well and provided model performance as satisfactory as the LS-SVM model. The CSA approach shows that fewer control and training parameters are required for model simulation as compared with the LS-SVM approach. The ability of a CSA approach in resolving limited data samples, non-linear sample function and multidimensional pattern recognition makes it a powerful tool in modelling the prediction of effluent removals in an SSTP.
Electrocoagulation (EC) is one of the emerging technologies in groundwater and wastewater treatment as it combines the benefits of coagulation, sedimentation, flotation, and electrochemical oxidation processes. Extensive research efforts implementing EC technology have been executed over the last decade to treat chemical oxygen demand (COD)-rich industrial wastewaters with the aim to protect freshwater streams (e.g., rivers, lakes) from pollution. A comprehensive review of the available recent literature utilizing EC to treat wastewater with high COD levels is presented. In addition, recommendations are provided for future studies to improve the EC technology and broaden its range of application. This review paper introduces some technologies which are often adopted for industrial wastewater treatment. Then, the EC process is compared with those techniques as a treatment for COD-rich wastewater. The EC process is considered as the most privileged technology by different research groups owing to its ability to deal with abundant volumes of wastewater. After, the application of EC as a single and combined treatment for COD-rich wastewaters is thoroughly reviewed. Finally, this review attempts to highlight the potentials and limitations of EC. Related to the EC process in batch operation mode, the best operational conditions are found at 10 V and 60 min of voltage and reaction time, respectively. These last values guarantee high COD removal efficiencies of > 90%. This review also concludes that considerably large operation costs of the EC process appears to be the serious drawback and renders it as an unfeasible approach for handling of COD rich wastewaters. In the end, this review has attempted to highlights the potential and limitation of EC and suggests that vast notably research in the field of continuous flow EC system is essential to introduce this technology as a convincing wastewater technology.
Single chambered up-flow membrane-less microbial fuel cell (UFML MFC) was developed to study the feasibility of the bioreactor for decolorization of Acid Orange 7 (AO7) and electricity generation simultaneously. The performance of UFML MFC was evaluated in terms of voltage output, chemical oxygen demand (COD) and color removal efficiency by varying the concentration of AO7 in synthetic wastewater. The results shown the voltage generation and COD removal efficiency decreased as the initial AO7 concentration increased; this indicates there is electron competition between anode and azo dye. Furthermore, there was a phenomenon of further decolorization at cathode region which indicates the oxygen and azo dye are both compete as electron acceptor. Based on the UV-visible spectra analysis, the breakdown of the azo bond and naphthalene compound in AO7 were confirmed. These findings show the capability of integrated UFML MFC in azo dye wastewater treatment and simultaneous electricity generation.
In this study, yeast microbial fuel cells (MFCs) were established as biosensors for in-situ monitoring of dissolved oxygen (DO) levels in environmental waters, with yeast and glucose substrates acting as biocatalyst and fuel, respectively. Diverse environmental factors, such as temperature, pH and conductivity, were considered. The sensor performance was first tested with distilled water with different DO levels ranging from 0 mg/L to 8 mg/L and an external resistance of 1000 Ω. The relationship between DO and current density was non-linear (exponential). This MFC capability was further explored under different environmental conditions (pH, temperature and conductivity), and the current density produced was within the range of 0.14-34.88 mA/m2, which increased with elevated DO concentration. The resulting regression was y = 1.3051e0.3548x, with a regression coefficient (R2) = 0.71, indicating that the MFC-based DO meter was susceptible to interference. When used in environmental water samples, DO measurements using MFC resulted in errors ranging from 6.25 % to 15.15 % when compared with commercial DO meters. The simple yeast-based MFC sensors demonstrate promising prospects for future monitoring in a variety of areas, including developing countries and remote locations.
A new commercial cationic polyelectrolyte chitosan (CM), obtained from the waste of mushroom production, was examined using models of water and wastewater namely kaolin and palm oil mill effluent (pome). As it is biocompatible, widely available, and economically feasible, chitosan mushroom has high potential to be a suitable replacement for alum. Also, it can be a promising alternative to chitosan obtained traditionally from Crustaceans due to its higher zeta potential and homogeneity based on the raw material required for its production. A wide range of coagulant dose (5-60 mg l(-1)) and wastewater pH (2-12) were taken into account to find the optimal conditions of coagulation. The optimal doses are 10 and 20 mg l(-1) at best pH (11 and 3) when treated with kaolin and palm oil mill effluent, respectively, while 1200 mg l(-1) of alum was not enough to reach the efficiency of chitosan mushroom. On the other hand, the optimum dose of chitosan mushroom (20 mg l(-1)) at pH 3 of pome produced (75, 73, and 98%) removal of chemical oxygen demand (COD), biological oxygen demand (BOD), and total suspended solids (TSS), respectively. The significant potential of chitosan mushroom was proved by zeta potential measurement. Indeed, it possesses the highest zeta potential (+70 mV) as compared to the traditional chitosan produced from crustaceans. In short, chitosan mushroom as a biocoagulant is eco-friendly and it enhances water quality that meets the requirements of environmental conservatives.
The Malaysian Department of Environment-Water Quality Index (DOE-WQI) was determined for the Terengganu River basin which is located at the coastal water of the southern South China Sea between July and October 2008. Monthly samplings were carried out at ten sampling stations within the basin. Six parameters listed in DOE-WQI were measured based on standard methods: pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS) and ammonical nitrogen (AN). The results indicated the impact of various anthropogenic activities which contribute to high values of BOD, COD, TSS and AN at middle and downstream stations, as compared with the upstream of the basin. The reverses were true for the pH and DO values. The DOE-WQI ranged from 71.5-94.6% (mean 86.9%), which corresponded to a classification status range from slightly polluted to clean. With respect to the Malaysia National Water Quality Standards (NWQS), the level of most of the parameters measured remained at Class I which is suitable for the sustainable conservation of the natural environment, for water supply without treatment and as well as for very sensitive aquatic species. It is suggested that monitoring should be carried out continuously for proper management of this river basin.
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.
The present study investigates the formation of aerobic granular sludge in sequencing batch reactor (SBR) fed with palm oil mill effluent (POME). Stable granules were observed in the reactor with diameters between 2.0 and 4.0mm at a chemical oxygen demand (COD) loading rate of 2.5 kg COD m(-3) d(-1). The biomass concentration was 7600 mg L(-1) while the sludge volume index (SVI) was 31.3 mL g SS(-1) indicating good biomass accumulation in the reactor and good settling properties of granular sludge, respectively. COD and ammonia removals were achieved at a maximum of 91.1% and 97.6%, respectively while color removal averaged at only 38%. This study provides insights on the development and the capabilities of aerobic granular sludge in POME treatment.
With inoculum sludge from a conventional activated sludge wastewater treatment plant, three sequencing batch reactors (SBRs) fed with synthetic wastewater were operated at different high temperatures (30, 40 and 50±1°C) to study the formation of aerobic granular sludge (AGS) for simultaneous organics and nutrients removal with a complete cycle time of 3h. The AGS were successfully cultivated with influent loading rate of 1.6CODg(Ld)(-1). The COD/N ratio of the influent wastewater was 8. The results revealed that granules developed at 50°C have the highest average diameter, (3.36mm) with 98.17%, 94.45% and 72.46% removal efficiency observed in the system for COD, ammonia and phosphate, respectively. This study also demonstrated the capabilities of AGS formation at high temperatures which is suitable to be applied for hot climate conditions.
In this study, we assessed and optimized a low-dissolved-oxygen oxic-anoxic (low-DO OA) process to achieve a low-cost and sustainable solution for wastewater treatment systems in the developing tropical countries treating low chemical oxygen demand-to-nitrogen ratio (COD/N) wastewater. The low-DO OA process attained complete ammonia removal and the effluent nitrate nitrogen (NO3-N) was below 0.3 mg/L. The recommended hydraulic retention time and sludge retention time (SRT) were 16 h and 20 days, respectively. The 16S rRNA sequencing data revealed that long SRT (20 days) encouraged the growth of nitrite-oxidizing bacteria (NOB) affiliated with "Candidatus Nitrospira defluvii". Comammox made up 10-20% of the Nitrospira community. NOB and comammox related to Nitrospira were enriched at long SRT (20 days) to achieve good low-DO nitrification performance. The low-DO OA process was efficient and has simpler design than conventional processes, which are keys for sustainable wastewater treatment systems in the developing countries treating low COD/N wastewater.
This study evaluates the effects of subcritical hydrothermal treatment on palm oil mill effluent (POME) and its concomitant formations of solid hydrochar, liquid product and gaseous product. The reactions were carried out at temperatures ranged 493 K-533 K for 2 h. The highest reduction of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were 58.8% and 62.5%, respectively, at 533 K. In addition, the removal of total suspended solids (TSS) achieved up to 99%, with the pH of POME reaching 6 from the initial pH 4. The gas chromatography coupled with mass spectroscopy (GC-MS) analysis showed that the fresh POME contained n-Hexadecanoic acid as the dominant component, which gradually reduced in the liquid product in the reaction with increased temperature, in addition to the attenuation of carboxyl compounds and elevation of phenolic components. The gaseous products contained CO2, CO, H2, and C3 - C6 hydrocarbons. Traces of CH4 were only found at 533 K. CO2 is the dominant species, where the highest of 3.99 vol% per 500 mL working volume of POME recorded at 533 K. The solid hydrochars showed negligible morphological changes across the reaction temperature. The O/C atomic ratio of the hydrochar range from 0.157 to 0.379, while the H/C atomic ratio was in the range from 0.930 to 1.506. With the increase of treatment temperature, the higher heating value (HHV) of the hydrochar improved from 24.624 to 27.513 MJ kg-1. The characteristics of hydrochar make it a fuel source with immense potential. POME decomposed into water-soluble compounds, followed by deoxygenation (dehydration and decarboxylation) in producing hydrochar with lower oxygen content and higher aromatic compounds in the liquid product. Little gaseous hydrocarbons were produced due to subcritical hydrothermal gasification at low temperature.
The present study describes the phytoremediation performance of water lettuce (Pistia stratiotes L.) for physicochemical pollutants elimination from paper mill effluent (PME). For this, pot (glass aquarium) experiments were conducted using 0% (BWW: borewell water), 25%, 50%, 75%, and 100% treatments of PME under natural day/light regime. Results of the experiments showed that the highest removal of pH (10.75%), electrical conductivity (EC: 63.82%), total dissolved solids (TDS: 71.20%) biological oxygen demand (BOD: 85.03%), chemical oxygen demand (COD: 80.46%), total Kjeldahl's nitrogen (TKN: 93.03%), phosphorus (P: 85.56%), sodium (Na: 91.89%), potassium (K: 84.04%), calcium (Ca: 84.75%), and magnesium (Mg: 83.62%), most probable number (MPN: 77.63%), and standard plate count (SPC: 74.43%) was noted in 75% treatment of PME after treatment by P. stratiotes. PCA showed the best vector length for TKN, Na, and Ca. The maximum plant growth parameters including, total fresh biomass (81.30 ± 0.28 g), chlorophyll content (3.67 ± 0.05 mg g-1 f.wt), and relative growth rate (0.0051 gg-1 d-1 ) was also measured in 75% PME treatment after phytoremediation experiments. The findings of this study make useful insight into the biological management of PME through plant-based pollutant eradication while leftover biomass may be used as a feedstock for low-cost bioenergy production. PRACTITIONER POINTS: Biological treatment of paper mill effluent using water lettuce is presented. Best reduction of physicochemical and microbiological pollutants was attained in 75% treatment. Maximum production of chlorophyll, plant biomass, and highest growth rate was also observed in 75% treatment.
Large volumes of untreated palm oil mill effluent (POME) pose threat to aquatic environment due to the presence of very high organic content. The present investigation involved two pilot-scale anaerobic expanded granular sludge bed (EGSB) reactors, continuously operated for 1 year to treat POME. Setting HRT at 9.8 d, the anaerobic EGSB reactors reduced COD from 71179 mg/L to 12341 mg/L and recycled half of sludge by a dissolved air flotation (DAF). The average effluent COD was 3587 mg/L with the consistent COD removal efficiency of 94.89%. Adding cationic polymer (PAM) dose of 30 mg/L to DAF unit and recycling its half of sludge caused granulation of anaerobic sludge. Bacilli and small coccid bacteria were the dominant microbial species of the reactor. The reactor produced 27.65 m(3) of biogas per m(3) of POME which was utilized for electricity generation.
The biodegradation characteristics of palm oil mill effluent (POME) and the related microbial community were studied in both actual sequential anaerobic ponds in Malaysia and enrichment cultures. The significant degradation of the POME was observed in the second pond, in which the temperature was 35-37 °C. In this pond, biodegradation of major long chain fatty acids (LCFA), such as palmitic acid (C16:0) and oleic acid (C18:1), was also confirmed. The enrichment culture experiment was conducted with different feeding substrates, i.e. POME, C16:0 and C18:1, at 35 °C. Good recovery of methane indicated biodegradation of feeds in the POME and C16:0 enrichments. The methane production rate of the C18:1 enrichment was slower than other substrates and inhibition of methanogenesis was frequently observed. Denaturing gradient gel electrophoresis (DGGE) analyses indicated the existence of LCFA-degrading bacteria, such as the genus Syntrophus and Syntorophomonas, in all enrichment cultures operated at 35 °C. Anaerobic degradation of the POME under mesophilic conditions was stably processed as compared with thermophilic conditions.
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.
Salinity expressed as total dissolved solids (TDS), is the most challenging parameter in bioremediation of produced water which may inhibit the microbial activities and cause sedimentation problems. The present study explores the feasibility of using walnut shell as an inexpensive and accessible adsorbent-carrier for the immobilization of isolated halophilic microorganisms for treatment of synthetic oilfield produced water. The moving bed biofilm reactor (MBBR) was examined with influent chemical oxygen demand (COD) concentrations from 900 to 3600 mg L-1, TDS concentrations from 35,000-200,000 mg L-1, and cycle times from 24 to 72 h. Comparison of the MBBR with the conventional sequencing batch reactor (SBR) indicated that both systems operated at lower influent COD and TDS concentrations satisfactorily; but at higher TDSs (above 150,000 mg L-1) the MBBR was more resistant to the shocks of toxicity (salinity) and organic load relative to the SBR. Also, the effluent turbidity was lower and the free sludge settling property was more favorable in the MBBR with average sludge volume index (SVI) of 38.8 mL g-1 compared to the SBR with SVI of 98.09 mL g-1. Microbial identification confirmed the presence of eight dominant halophilic species which were hydrocarbon degraders and/or denitrifiers.
In this study, the potential of a pilot-scale granular activated carbon sequencing batch biofilm reactor (GAC-SBBR) for removing chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N) and 2,4-dichlorophenol (2,4-DCP) from recycled paper wastewater was assessed. For this purpose, the response surface methodology (RSM) was employed, using a central composite face-centred design (CCFD), to optimise three of the most important operating variables, i.e., hydraulic retention time (HRT), aeration rate (AR) and influent feed concentration (IFC), in the pilot-scale GAC-SBBR process for recycled paper wastewater treatment. Quadratic models were developed for the response variables, i.e., COD, NH3-N and 2,4-DCP removal, based on the high value (>0.9) of the coefficient of determination (R(2)) obtained from the analysis of variance (ANOVA). The optimal conditions were established at 750 mg COD/L IFC, 3.2 m(3)/min AR and 1 day HRT, corresponding to predicted COD, NH3-N and 2,4-DCP removal percentages of 94.8, 100 and 80.9%, respectively.
Water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) were analyzed to determine their effectiveness in aquaculture wastewater treatment in Malaysia. Wastewater from fish farm in Semanggol Perak, Malaysia was sampled and the parameters determined included, the pH, turbidity, dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrite phosphate (PO4(3-)), nitrate (NO(3-)), nitrite (NO(-2)), ammonia (NH3), and total kjedahl nitrogen (TKN). Also, hydroponics system was set up and was added with fresh plants weights of 150 +/- 20 grams Eichhornia crassipes and 50 +/- 10 grams Pistia stratiotes during the 30 days experiment. The phytoremediation treatment with Eichhornia crassipes had pH ranging from 5.52 to 5.59 and from 4.45 to 5.5 while Pistia stratiotes had its pH value from 5.76 to 6.49 and from 6.24 to 7.07. Considerable percentage reduction was observed in all the parameters treated with the phytoremediators. Percentage reduction of turbidity for Eichhornia crassipes were 85.26% and 87.05% while Pistia stratiotes were 92.70% and 93.69% respectively. Similar reductions were observed in COD, TKN, NO(3-), NH3, and PO4(3-). The capability of these plants in removing nutrients was established from the study. Removal of aquatic macrophytes from water bodies is recommended for efficient water purification.
Sustainable, environmental friendly, and safe disposal of sewage treatment plant (STP) sludge is a global expectation. Bioremediation performance was examined at different hydraulic retention times (HRT) in 3-10 days and organic loading rates (OLR) at 0.66-7.81 g chemical oxygen demand (COD) per liter per day, with mixed filamentous fungal (Aspergillus niger and Penicillium corylophilum) inoculation by liquid-state bioconversion (LSB) technique as a continuous process in large-scale bioreactor. Encouraging results were monitored in treated sludge by LSB continuous process. The highest removal of total suspended solid (TSS), turbidity, and COD were achieved at 98, 99, and 93%, respectively, at 10 days HRT compared to control. The minimum volatile suspended solid/suspended solid implies the quality of water, which was recorded 0.59 at 10 days and 0.72 at 3 days of HRT. In treated supernatant with 88% protein removal at 10 days of HRT indicates a higher magnitude of purification of treated sludge. The specific resistance to filtration (SRF) quantifies the performance of dewaterability; it was recorded minimum 0.049 × 10(12) m kg(-1) at 10 days of HRT, which was equivalent to 97% decrease of SRF. The lower OLR and higher HRT directly influenced the bioremediation and dewaterability of STP sludge in LSB process. The obtained findings imply encouraging message in continuing treatment of STP sludge, i.e., bioremediation of wastewater for environmental friendly disposal in near future.
This case study uses several univariate and multivariate statistical techniques to evaluate and interpret a water quality data set obtained from the Klang River basin located within the state of Selangor and the Federal Territory of Kuala Lumpur, Malaysia. The river drains an area of 1,288 km(2), from the steep mountain rainforests of the main Central Range along Peninsular Malaysia to the river mouth in Port Klang, into the Straits of Malacca. Water quality was monitored at 20 stations, nine of which are situated along the main river and 11 along six tributaries. Data was collected from 1997 to 2007 for seven parameters used to evaluate the status of the water quality, namely dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, suspended solids, ammoniacal nitrogen, pH, and temperature. The data were first investigated using descriptive statistical tools, followed by two practical multivariate analyses that reduced the data dimensions for better interpretation. The analyses employed were factor analysis and principal component analysis, which explain 60 and 81.6% of the total variation in the data, respectively. We found that the resulting latent variables from the factor analysis are interpretable and beneficial for describing the water quality in the Klang River. This study presents the usefulness of several statistical methods in evaluating and interpreting water quality data for the purpose of monitoring the effectiveness of water resource management. The results should provide more straightforward data interpretation as well as valuable insight for managers to conceive optimum action plans for controlling pollution in river water.