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Acid pretreatment is one of the most widely used fractionation processes for lignocellulosic biomass. In this study, effect of mineral acids (SA, HA, and NA) on recovery of reducing sugar from coconut coir was studied. The independent variables such as reaction time (X1, min) and concentration of acid (X2, % w/w) were optimized using Response Surface Methodology (RSM) for maximum yield of reducing sugar. In this study, 10% w/v of coir was pretreated under various conditions of X1 and X2 by maintaining a constant temperature (121oC). A maximum reducing sugar yield greater than 55% was observed for acid pretreatment.

The scarcity of water resources and environmental pollution have highlighted the need for sustainable wastewater treatment. Existing conventional treatment systems are energy-intensive and not always able to meet stringent disposal standards. Recently, algal-bacterial systems have emerged as environmentally friendly sustainable processes for wastewater treatment and resource recovery. The algal-bacterial systems work on the principle of the symbiotic relationship between algae and bacteria. This paper comprehensively discusses the most recent studies on algal-bacterial systems for wastewater treatment, factors affecting the treatment, and aspects of resource recovery from the biomass. The algal-bacterial interaction includes cell-to-cell communication, substrate exchange, and horizontal gene transfer. The quorum sensing (QS) molecules and their effects on algal?bacterial interactions are briefly discussed. The effect of the factors such as pH, temperature, C/N/P ratio, light intensity, and external aeration on the algal-bacterial systems have been discussed. An overview of the modeling aspects of algal-bacterial systems has been provided. The algal-bacterial systems have the potential for removing micropollutants because of the diverse possible interactions between algae-bacteria. The removal mechanisms of micropollutants ? sorption, biodegradation, and photodegradation, have been reviewed. The harvesting methods and resource recovery aspects have been presented. The major challenges associated with algal-bacterial systems for real scale implementation and future perspectives have been discussed. Integrating wastewater treatment with the algal biorefinery concept reduces the overall waste component in a wastewater treatment system by converting the biomass into a useful product, resulting in a sustainable system that contributes to the circular bioeconomy.

In this study, the efficiency of a trickling photo-bioreactor (TPBR), seeded with activated sludge and microalgae, was evaluated for domestic wastewater treatment. TPBR was operated completely on natural aeration at 2-, 4-, and 6-h hydraulic retention time (HRT) with a 12:12 h light: dark cycle. The total organic carbon (TOC) and total nutrient (TN) removal were negatively affected by decreasing the HRT from 6 to 2 h. The TPBR was able to reduce TOC from 93 to 9 mg/L, TN from 34 to 18 mg/L, and phosphorus from 23.5 to 4 mg/L at 6-h HRT. The chlorophyll concentration (5 – 7 mg per liter of sponge volume) was observed to be highest in the middle of the reactor. Altogether, 106 organic micropollutants of different classes like pharmaceutical, personal care products, pesticides, herbicides, and fungicides were detected in the influent wastewater sample. However, in the treated effluent, only 17 micropollutants were detected at 6-h HRT. This shows that the algal-bacterial consortia are capable of removing micropollutants from wastewater. The energy input was 0.06 kWh/kg COD removed which is much less than the conventional activated sludge processes. The results indicate that this novel system is capable of providing a sustainable wastewater treatment solution.

The accumulation of pith in a coconut husk processing facility leads to disposal problems, fire hazards, and contamination of groundwater. The leachate contains phenolic compounds that percolate through the soil and contaminate groundwater. Monolignols (guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H)) in soil and groundwater pose a threat to the land and water resources. This study focuses on minimizing waste accumulation by treating the accumulated pith with sodium hydroxide to recover lignin and sugar. Pith, which has about with 24% cellulose and 49% lignin, was used as a substrate for recovery of Kraft lignin (KL) and sugar. The operating condition for the recovery of KL was optimized using response surface methodology (RSM). Maximum KL recovery (~ 86%) was achieved with optimal biomass loading of 65 mg/ml, NaOH concentration 5.12% w/w, residence time 31 min, and temperature 121 °C. A glucose yield of 95% was obtained after 48 h of saccharification. The removal of the aromatic layer increased the crystallinity index (CrI) after hydrolysis from 65 to 81.7%. The S/G ratio of 0.49 indicated that the lignin structure of pith is a matrix with many branches, thus making the lignin matrix strong and rigid.

This research studied the effect of solids retention time (SRT) on algal-activated sludge (AAS) association in carbon-nitrogen-phosphorus removal and lipid synthesis from municipal wastewater. Five 500-mL test reactors were operated at different SRTs (2, 4, 6, 8, and 10 days) parallelly, in a draw-and-fill mode with external aeration. The organic carbon (C), nitrogen (N), and phosphorus (P) removal were positively correlated with SRT. The highest C, N, and P removal rates of 89, 73, and 91% were observed at 10-day SRT. The algal percentage was more than 60% in the mixed biomass at all the SRTs at a steady state. The lipid content ranged from 15 to 30% and declined with an increase in SRT, with 60% saturated and monounsaturated fatty acid at all the SRTs. The cetane number varied from 56 to 64 indicating a good-quality biofuel. The Fourier transform infrared spectroscopy transmittance spectrum for 10-day SRT biomass showed the presence of chloroalkane, alcohols, phenols, alkane, esters, allene, alkynes, and phosphine. The AAS system can be used as the main treatment unit for treating municipal wastewater in a single reactor with SRT greater than 4 days.

The present study focusses on improving the performance of a Continuous Bipolar Mode Electrocoagulation (CBME) system for removal of recalcitrant total organic carbon (TOC) and total phosphorus (TP...

Municipal wastewater treatment plants (WWTPs) could become valuable contributors to a circular economy by implementing the 3R principles (reduce, reuse, and recycle). While reducing the pollution load of sewage is the primary objective of a WWTP, this process generates several potentially valuable byproducts including treated effluent, biogas, and sludge. The effluent can be reused in various end use applications and biogas can be reused as a fuel (for electricity generation, transportation, and cooking) or a chemical feedstock. The sludge can either be directly recycled as soil conditioner or via thermochemical/biochemical processing routes to recover material (e.g., hydrochar), energy (e.g., heat, and syngas), and resource value (phosphorus). This work presents a five-layered assessment framework for quantitatively evaluating the sustainable value of municipal WWTPs by using life cycle assessment (LCA) and life cycle costing assessment (LCCA) tools. In addition, indicators reflecting potential benefits to stakeholders and society arising from investments into municipal WWTPs such as the private return on investment (PROI) and the environmental externality costs to investment ratio (EECIR). The framework is validated in a hypothetical case study where the sustainable value of a circularly managed municipal WWTP is evaluated in situations involving multiple byproduct utilization pathways. Four future circular options (FCOs) are examined for a 50,000 m3/d capacity WWTP treating sewage up to tertiary standards. The FCOs mainly differ in terms of how biogas is reused (to meet the WWTP's internal energy demands, as cooking fuel, or as fuel for city buses after upgrading) and how sludge is recycled (as soil conditioner or by producing hydrochar pellets for electricity generation). The FCO in which treated effluent is reused in industry, biogas is used as cooking fuel, and sludge is used as a soil conditioner provides the greatest sustainable value (i.e., the lowest private costs and environmental externality costs (EEC) together with high revenues), the highest PROI, and the lowest EECIR. The strengths and limitations of the proposed assessment framework are also discussed.

The effect of [Emim][OAc] on Celluclast 1.5 L, Accellerase 1500, and IL-tolerant (MSL2) cellulase during the saccharification of carboxymethylcellulose (CMC), Avicel (AV), rice straw (RS) was studied in one pot process (pretreatment and saccharification). The inhibition caused by [Emim][OAc] (0.5–2.0 M) with substrate loading (20–50 mg/mL) were also evaluated. In most cases, the inhibition mode of saccharification for CMC and AV was identified to be uncompetitive inhibition when the concentration of [Emim][OAc] was higher than 0.5 M. Under the influence of 0.5 M of [Emim][OAc], the Critical Concentration of Substrate (CCS) values of the Celluclast 1.5 L and Accellerase 1500 on CMC hydrolysis were determined to be at 26.59 and 33.65 mg/mL, respectively. Also, increasing in [Emim][OAc] concentration could increase in CCS values, suggesting the positive effect of [Emim][OAc] on the improvement of enzymatic saccharification. This study provides insight into the process optimization for integration of [Emim][OAc] in one pot process of biorefinery.

Sulphuric acid hydrolysis of coconut coir under case I (time: 2–10 min; temperature: 160–240 °C; acid concentration: 0.2–0.7% w/w) and case II (time: 10–60 min; temperature: 100–160 °C; acid concentration: 0.7–2% w/w) was studied. The optimal conditions for maximum recovery of reducing sugar for case I and case II were 8.2 min, 200 °C, and 0.21% w/w acid; and 13 min, 155 °C, and 1.27% w/w acid. Under these conditions, 52% and 48% of reducing sugar were recovered. Enzymatic saccharification was performed after hydrolysis using cellulase and β-glucosidase enzymes. Glucose yields of 90% and 55% were obtained in case I and case II, respectively. Changes in structure and functional groups in solid were observed when studied using SEM, XRD, and FTIR. The aromatic layer was removed in case I and cellulose layer was exposed. Crystallinity increased from 42 to 54% in case I and from 42 to 45% in case II.

Phosphorus is known to be a limited non-renewable resource. Phosphorus is obtained from phosphate rock, which is likely to be depleted in the next few decades. Therefore, it is very important to find alternate sources of phosphorus from which phosphorus can be recycled and recovered. This study focuses on the recovery of phosphorus from the sludge generated from a continuous bipolar mode electrocoagulation (CBME) system, used for treating a palm oil mill effluent (POME). The sludge generated from the CBME system is leached with oxalic acid and sulphuric acid for phosphorus recovery with and without thermal treatment. Acid leaching was carried out at various time intervals using various liquid/solid (L/S) ratios of acids and sludge. The CBME system caused a 73% removal of phosphorus from POME, where phosphorus is precipitated in sludge as iron phosphates or adsorbed as phosphates depending on the pH in the system. Acid leaching resulted in nearly 85% recovery of phosphorus with both sulphuric acid and oxalic acid for sludge combusted at 900 °C. Statistical analysis was carried out to find the significance of the operational conditions on the phosphorus yield. Acid leaching results in the formation of orthophosphates, which can be used as a raw material for synthesis of chemical fertilizers.

Dewaxing effects on the pretreatment, saccharification and fermentation are rarely reported due to the low abundance of wax in lignocellulose. This study aimed to investigate the effect of wax removal on saccharification and ethanol yield from lignocellulose by using Rice straw (RS), Napier grass (NG), and sugarcane bagasse (SB). The wax contents of 0.56%, 1.7%, and 0.6% were obtained from RS, NG and SB after the wax extraction, respectively. The alkaline pretreatment was applied in combination with dewaxing to decipher the synergistic effect of these treatments. Dewaxing and alkaline pretreatment of lignocellulosic biomass showed changes in the plant compositions. Removal of wax from RS, NG and SB showed significant changes in the surface morphology and functional groups. A higher yield of sugars and ethanol was observed in dewaxed and alkaline pretreated samples. The ethanol yields of 75.4%, 89.85%, and 74% from RS, NG, and SB were obtained after fermentation, respectively.

Agriculture is the mainstay of the Indian economy. The agro-based industries produce high volumes of highstrength wastewaters that need to be treated and reused to prevent environmental pollution and water wastage. This study evaluated the performances of a sequential biological-electrochemical process for treating an anaerobically digested effluent of a Marigold flower processing agro-industry. The uniqueness of this wastewater possess a major challenge to its treatment since not many studies have been conducted on this wastewater. The biological treatment was carried out in a Sequential Batch Reactor (SBR). The treated water was further polished in a Continuous Bipolar-mode Electrochemical Reactor (ECR) to remove the residual organics. The anaerobically digested effluent Chemical Oxygen Demand (COD), Dissolved Organic Carbon (DOC), Total Nitrogen (TN), Total Phosphorus (TP) and Total Suspended Solids (TSS) were 5750 ± 991 mg/L, 980 ± 120 mg/L, 692 ± 60 mg/L, 9.7 ± 1.1 mg/L, and 1144 ± 166 mg/L, respectively. A significant level of treatment was achieved in the SBR. The combined system was able to remove 79% of COD, 85% of DOC, 53% of TN, and almost 100% of TP, TSS, and Volatile Suspended Solids (VSS). Several organic compounds belonging to the category of natural plants compound, pesticide, fungicide, etc. were detected in the raw wastewater. Most of the compounds were almost completely removed by the treatment system. The final effluent was almost colorless and free from suspended solids. However, for reuse, the water needs to be further treated in an advanced oxidation process.

The main objective of this research was to study the feasibility of using algal and algal-activated sludge systems in treating laundry wastewater. Three different types of systems—green microalgae (system A), diatoms + activated sludge (system B), and green microalgae + activated sludge (system C)—were studied at six different solid retention times (SRT)—6, 8, 10, 12, 14, and 16 days—to evaluate their performance in removal of total organic carbon (TOC), total nitrogen (TN), anionic surfactants, and micropollutants with added trace elements. System B showed relatively better performance in removal of TOC (79%) and TN (90%). A total of 64 compounds were detected in influent when analyzed by LC-MS, of which 19 were grouped under herbicides, pesticides, and insecticides, 25 under pharmaceuticals, and 20 under others. Linear alkylbenzene sulfonate (LAS) was detected only in the effluent of system A and was not detected in both system B and system C. Grotan OX, an anti-microbial, was the compound with least removal in all the systems. The bacterial LAS degrader/tolerant plate count in system B at 16-day SRT was 2000 CFU/mL, 50 times more than the plate count of system C (40 CFU/mL). The LAS degrader/tolerant bacterial species identified were Aeromonas caviae and Klebsiella pneumonia in both systems B and C. The LAS degrader/tolerant green microalgae plate count at 16-day SRT was 130 CFU/mL, whereas no LAS degrader/tolerant diatom colonies were observed.

This study compares the performance of two different systems (i) immobilized microalgae and suspended activated sludge (System A) and (ii) suspended co-culture (System B) in simultaneous treatment and biofuel production from domestic wastewater at different HRTs. The System A showed higher lipid content and carbon, nitrogen and phosphorous removal (40, 88, 91, and 93%) than System B (16, 87, 58, and 80%). C18:0 and C18:1n9t are dominant fatty acids observed in System A and C16:0 and C18:1n9t in System B. The immobilization of microalgae exhibited more benefits than suspended co-culture in terms of treatment and biofuel production.

The objective of this study was to examine the performance of mixed microalgal bioreactors in treating three different types of wastewaters-kitchen wastewater (KWW), palm oil mill effluent (POME), and pharmaceutical wastewater (PWW) in semi-continuous mode and to analyze the lipid content in the harvested algal biomass. The reactors were monitored for total nitrogen and phosphate removal at eight solid retention times (SRTs): 2, 4, 6, 8, 10, 12, 14, and 16 days. The nutrient uptake kinetic parameters were quantified using linearized Michaelis-Menten and Monod models at steady-state conditions. The nutrient removal efficiency and lipid production were found to be higher in KWW when compared with the other wastewaters. Saturated fatty acids (C16:0, C18:0, and C18:1) accounted for more than 60% of the algal fatty acids for all the wastewaters. The lipid is, therefore, considered suitable for synthesizing biodiesel.

Microalgae-based treatment systems have been successfully used for the polishing of domestic wastewater. Research is underway in studying the suitability of using these systems as main treatment units. This study focuses on comparing the performances of a mixed microalgal culture and an aerobic bacterial culture, based on the kinetic evaluation, in removing organic carbon from a kitchen wastewater. The two systems were operated at six different solid retention times (SRTs)—2, 4, 6, 8, 10, and 12 days in continuous mode. The influent and effluent samples were analyzed for chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (TN), phosphates, and surfactants. Steady-state kinetics (k, Ks, Y, and kd) for organic carbon removal were obtained by fitting experimental data in linearized Michaelis-Menten and Monod equations. The mixed microalgal system showed similar or better performance in COD and TN removal (88 and 85%, respectively) when compared with the COD and TN removal by the aerobic bacterial system (89 and 48%). A maximum lipid yield of 40% (w/w of dry biomass) was observed in the microalgal system. Saturated fatty acids accounted for 50% of the total observed FAME species. The study indicates that the mixed microalgal culture is capable of treating kitchen wastewater and has the potential to replace aerobic bacteria in biological treatment systems in certain cases.

Inorganic acids, such as sulphuric acid, hydrochloric acid, and nitric acid are widely used for the pretreatment of lignocellulosic biomass for bioenergy production. In this study, the effect of different acids on the recovery of reducing sugar from coconut residues (coir and pith) mixed in different ratios was studied. The pretreatment conditions for different acids were optimized using response surface methodology (RSM). The independent variables, such as biomass ratio, time and acid concentration were considered for the optimization studies with reducing sugar as the dependent variable. The maximum recovery of reducing sugar (45%) from mixed biomass was observed during nitric acid (NA) pretreatment. The recovery of reducing sugar was lower for hydrochloric acid (HA) and sulphuric acid (SA). The lower yield was attributed to the possible formation of sugar degradation compounds during acid pretreatment. Therefore, NA pretreatment was found suitable for mixed biomass compared to other acids. Further studies are required to understand the effect of NA pretreatment through a detailed study of liquid hydrolysate and the introduction of the saccharification process. Mixed biomass benefits the biorefinery industries for sustainable bioenergy production.

Light is the main energy source for microalgae, and the intensity and wavelength of light influence cell metabolism and biomass composition, which, in turn, affects wastewater treatment. The objective of this study is to examine how different light intensities and light wavelengths affect the growth of mixed algal-bacterial culture while treating sewage. Three different light intensities (100, 200, and 300 μmol/m2-s) of four different light wavelengths (blue, red, white, and yellow) were selected for this study. The dissolved organic carbon (DOC), dissolved nitrogen (DN), and dissolved phosphorus (DP) in influent and effluent samples were measured, along with chlorophyll content in the biomass. The highest chlorophyll concentration of 3.5 mg/L was observed at 100 μmol/m2-s intensity of red light. The concentration of chlorophyll decreased as light intensity increased, with exception of white light. The highest DOC removal of 84% was observed at 300 μmol/m2-s intensity of blue light whereas the highest DN (51%) and DP (80%) removal was observed with a red light intensity of 100 μmol/m2-s. Overall, blue light with an intensity of 300 μmol/m2-s and red light with an intensity of 100 μmol/m2-s were found to be the most efficient at removing carbon and nutrients. The results suggested that the color and intensity of light influence algal-bacterial growth and wastewater treatment efficiency.

The effects of time (10–60 min) and temperature (250–350°C) on TOCcrude and biochar yields from coir and pith through hydrothermal liquefaction (HTL) process was investigated. The parameters were optimized for minimum biochar and maximum total organic carbon (TOC) in aqueous crude using response surface methodology (RSM). The optimal time and temperature for HTL of coir and pith were 35 min, 302°C, and 35.2 min, 300°C, respectively. Higher biomass conversion and bio-oil yield of 87.34%, 83.76% and 34.6%, 32.72%, was observed for coir and pith, respectively. The biochar yield for coir and pith was reduced from 40 to 12.66% and 34–16.24%. The oxygen and carbon content in the HTL products such as heavy bio-oil (HBO), light bio-oil (LBO) were lower and higher increasing the High Heating Value (HHV), respectively. The HHV of HBO, and LBO for coir and pith were 31 MJ/kg, 22 MJ/kg and 28 MJ/kg, 19 MJ/kg, respectively. The GC-MS/MS analysis revealed that the oil was a mixture of compounds such as alcohols, aldehydes, ketones, amines, amides, esters, ethers, phenols, and their derivatives. Therefore, the conversion of coir and pith to bio-oil can be effectively achieved through the HTL process.

Consumption of detergents containing linear alkyl benzene sulfonate (LAS) and fluorescent whitening agents (FWAs) is increasing rapidly in Asian countries. A respirometric oxygen uptake method was conducted to examine the aerobic biodegradability of some of the commercially available laundry and dishwashing detergents of India, Japan, Indonesia, and Thailand. Indian detergents and Japanese detergents showed 95–100% of LAS removal. However, the three-dimensional fluorescent spectra results indicated the presence of residual metabolites such as sulfophenyl carbonate. Indonesian detergents and Thai detergents showed less LAS removal, but the progress of benzene ring cleavage of LAS in these detergents was observed from the test results. The FWAs were observed mainly in laundry detergents. The removal of FWAs during biodegradation test was observed to be between 12.4 and 78.8%. The complex changes in oxygen uptake curve during the test period suggested the presence of various organic compounds in the detergents. The tested detergents were classified into three clusters based on the relationship between the total organic carbon and the fluorescence (220/290 nm) removals. The diverse biodegradation results among the tested detergents from different Asian countries suggested the effects of various ingredients present in the detergents.

Ethanol production from acid pretreated food waste hydrolysate using immobilized Saccharomyces cerevisiae 74D694 was investigated under different conditions in a batch experiment. Ethanol yield was measured at different time intervals (38, 48, 72, 96 and 105 h) using different immobilized bead ratios (25:100, 30:100, 40:100, 50:100 and 54:100, w/v). Food waste was pretreated using dilute sulphuric acid and the hydrolysate was filtered. The dry food waste had an initial reducing sugar content of 46% (w/w). After dilute acid pretreatment, reducing sugar content increased to 62%. The present study utilized liquid hydrolysate for ethanol production. The process was optimized using central composite design (CCD) a statistical tool used for optimization in response surface methodology (RSM). RSM predicted a maximum ethanol yield of 0.044 g/g of soluble solid in liquid hydrolysate at 40 h fermentation time and immobilized bead ratio of 54:100 (w/v). An experiment was run at the optimal condition and an ethanol yield of 0.047 g/g of soluble solid in liquid hydrolysate was obtained. The predicted result was thus experimentally verified.

Manufacturing industries synthesize new chemical products every day, which eventually find their way into domestic and industrial wastewaters. As a result, wastewater is becoming increasingly more complex in nature. The emerging pollutants escape the treatment systems and appear in the receiving water bodies. Wastewater treatment plants in India still report effluent parameters in terms of biological oxygen demand (BOD) and chemical oxygen demand (COD) at the ppm level, whereas these emerging pollutants, many of whom are non-biodegradable, can be toxic and carcinogenic at the ppb level. Therefore, it is imperative to look for alternatives or upgrade the existing systems which safely remove these harmful compounds from wastewater. In this research, efficiency of electrocoagulation process was assessed in a laboratory-scale setup in removing recalcitrant carbon from a real wastewater. The wastewater was collected from an effluent treatment plant that receives domestic wastewater and industrial effluents from chemical, bulk drugs and allied industries, for treatment. In this study, the wastewater sample was analyzed for total dissolved solids (TDS) and total organic carbon (TOC), and then treated biologically in a respirometer using aerobic microorganisms. After the oxygen uptake curve plateaued, indicating a cessation of biological process, the sample was analyzed for TDS and TOC and put in a lab-scale electrocoagulation setup. Iron and Aluminium electrodes were used in the study and efficiency of the system in removing the recalcitrant/residual carbon and TDS was studied with respect to the reaction time. The results showed that electrocoagulation can be a potential post-biological treatment system for removal of recalcitrant carbon from wastewaters.

This study describes a laboratory-scale continuous-flow bipolar mode electrocoagulation (CBME) unit that was developed as a downstream process unit for polishing an anaerobically treated pa...

This study aims to enhance nutrient removal in an existing activated sludge process based decentralized wastewater treatment system by introducing illumination and algal biofilms in the aeration chamber. The aeration tank (AT) has been modified with the addition of blue light-emitting diode (LED) lights and silicon carbide foam filters as supporting media for algal biofilm growth. The light intensity (varied between 100 and 200 W/180 m3) had shown a strong correlation with the chlorophyll concentration in the mixed liquor. The nitrogen removal has increased from 48 ± 9% to 63 ± 6% and P removal from 37 ± 12% to 70 ± 12% in the modified aeration tank using 200 W LEDs with 12:12 light: dark cycle. Decreasing the light period to 8-h had decreased the carbon and nutrient removal to 32 ± 11% and 45 ± 10% respectively. The influent C/N showed a strong association with carbon and nutrient removal.

Micropollutant removal efficiencies of two trickling filters – operated under light and dark conditions were studied and compared. Linear alkylbenzene sulphonate (LAS) and caffeine were selected as model micropollutants. Both lab-scale trickling-filter type reactors were packed with polyurethane foam sponge cubes (2 cm × 2 cm × 2 cm) with 40% occupancy. The trickling filter with the white color LED light was named as Light Reactor (LR), which was operated under light: dark cycle of 12:12 h with a quantum flux of 15 μmoles/m2/s. No light was provided in the other trickling filter, named Dark Reactor (DR). Synthetic wastewater containing glucose (250 mg/L), LAS (12 mg/L), and caffeine (0.05 mg/L) was fed to the reactors at a hydraulic retention time (HRT) of 12- and 8-h at 25 °C for 2 months. The C, N, and P removal at 12-h HRT were 85%, 15%, and 49%, respectively, in LR, the corresponding values in DR were 88%, 18%, and 43%. Similarly, at 8-h HRT 90%, 24%, and 37% was observed in LR and 84%, 19%, and 37% in DR. However, the LAS and caffeine removal decreased from 99 to 96% and 96 to 86% respectively in LR, and from 96 to 79% in DR with decreasing the HRT from 12 to 8-h. The number of LAS degraders in LR (5.5 × 104 CFU/sponge cube) was higher compared to DR (2.2 × 104 CFU/sponge cube) at 8-h HRT. The above results indicate that algal-bacterial symbiotic relationship in LR was beneficial for carbon and micropollutants removal from domestic wastewater.

Agro-industrial wastewaters are generated in large volumes with high organic content. It is very difficult to eliminate the recalcitrant organic compounds present in the wastewater after the biological treatment. Monopolar-mode electrocoagulation systems are extensively studied in the literature as polishing treatment systems after the biological treatment. However, studies on bipolar-mode electrocoagulation systems are limited. This study compares the performance of a Continuous Bipolar-Mode Electrocoagulation (CBME) unit developed at a laboratory scale with that of a field-scale CBME system used for the removal of recalcitrant organic carbon and phosphorus from marigold wastewater. The design parameters required for a CBME system were extracted. The higher Surface area to Volume (S/V) ratio of 76.5 m-1, used in this study achieves higher treatment efficiency at lower energy consumption and lesser retention time, which saves energy and space when applied in field scale. The optimization study was carried out at both lab-scale and field-scale for the removal of Total Organic Carbon (TOC) and Total Phosphorus (TP) using Response Surface Methodology (RSM). The S/V ratio was kept constant, for both the CBME systems. The potential design parameters and the performance of the CBME reactors were compared. The optimum values obtained for operating variables were found to be, pH at 6.5, retention time of 6.8 min and current at 2.9 A for lab-scale system and the optimum values obtained for field-scale system were found to be, the retention time of 6.5 min and current at 51.3 A. The organic compounds were identified in the wastewater samples at the optimum points. Retention time, S/V ratio, and energy consumption were found to be potential design parameters for a CBME system.

Attempts have been made in this study to recover reducing sugar from coconut pith by pretreating the pith with a mineral acid (sulphuric acid) and an organic acid (oxalic acid). Pretreatment was carried out in a high pressure batch reactor (HPBR). Biomass loading, reaction time, temperature and acid concentration were chosen as operating parameters. Response Surface Method (RSM) was used to determine the optimum condition. When 87 mg / ml of biomass was treated with 7.56% (w/w) oxalic acid at $134^{\circ}\mathrm {C}$ for 35 min, 62% reducing sugar was recovered. On the other hand, a recovery of 62% reducing sugar was observed when 79 mg/ml of biomass loading with 2.01% (w/w) sulphuric acid was treated at $127^{\circ}\mathrm {C}$ for 50 min. In summary, considering the acid concentration, it was found that pretreatment of oxalic acid is effective for recovering reducing sugars from coconut pith In addition, 33% of glucose yield was observed in the enzymatic saccharification of the oxalic acid pretreated solids in 96 h. In order to investigate morphological changes before and after pretreatment, pith was examined using FTIR, XRD, SEM.

This research was conducted in a batch mode in a laboratory-scale setup to study (1) the biodegradation of laundry wastewater under aerobic and anaerobic conditions and to quantify the degradation at steady-state in terms of kinetic parameters and (2) the inhibition caused by laundry wastewater on growth-substrate utilization by un-acclimated ethanol-enriched aerobic and anaerobic microbial cultures. The chemical oxygen demand (COD) removal was above 95% under aerobic condition; however, the COD removal varied between 70 and 88% under anaerobic condition. The steady-state kinetic parameters k, Ks, Y, μm, and kd were 1.75 d-1, 21.67 mg COD/L, 0.4 mg volatile suspended solids (VSS)/mg COD, 0.7 d-1, and 0.06 d-1 respectively under aerobic condition; corresponding values under anaerobic condition were 4.7 d-1, 173.67 mg COD/L, 0.06 mg VSS/mg COD, 0.3 d-1, and 0.04 d-1. Laundry wastewater caused a competitive inhibition at doses above 200 mg/L under aerobic and anaerobic conditions.

A simulated high-strength [chemical oxygen demand (COD) ∼85,000 mg/L] wastewater containing primarily acrylic acid, acetic acid, and formaldehyde was treated in an anaerobic membrane bioreactor. The reactor consisted of a 25 L complete-mix tank fitted with three Kubota flat-panel membrane cartridges. The reactor was operated at an organic loading rate of 3.4 kg COD/m3-day. More than 99% removal of COD and formaldehyde was achieved. Acrylic acid concentration in the effluent stream was below the detection limit. This preliminary study, which lasted for 45 days, showed the potential of application of anaerobic membrane bioreactors in treatment of high-strength wastewaters containing toxic substances like acrylic acid and formaldehyde.

The cultures from a sucrose-fed anaerobic acid reactor were dosed with 0, 60, 100, 200, 400, 800 and 1,500 mg/L, of a mixture of three Procion reactive dyes, Red MX-8B, Red MX-5B and Orange MX-2R, in order to study the colour removal and the toxic effect of the dyes on anaerobic acidification of sucrose. Sucrose undergoes a possible extracellular transformation into intermediate substances before being taken up by the acidogens for volatile fatty acid (VFA) synthesis. The rate and the extent of this uptake is unaffected by the presence of dyes. The dyes, however, reduced the rate of synthesis of VFA, and considerably diminished the VFA production potential of sucrose. The acidification stopped, likely due to an inhibition caused by VFA accumulation. As a result, only 50–60% of the soluble organic carbon was utilised for VFA synthesis. The removal of colour by the unacclimated anaerobic acidogenic biomass takes place by adsorption. However, Freundlich's adsorption constants did not suggest a favourable adsorption.

A continuous bipolar mode electrocoagulation (CBME) unit was used in this study for polishing a biologically treated distillery wastewater at laboratory scale. This study focuses on optimizing the process for removal of Total Organic Carbon (TOC) from an anaerobically-treated distillery wastewater. Response surface methodology (RSM) was used for optimizing the process. The study was conducted by varying three operating parameters: Initial pH (2-10), reaction time (0.5-15 min), and current density (13-40 A/sqm). High R-square values, above 0.9, were obtained with ANOVA. Optimal point was observed to be at pH-6.04, Reaction time-11.63 min, current density-39.2 A/sqm. Experimental values of TOC removal at optimal point were found to be 73% against maximum predicted value of 79%. Color removal efficiency was observed to be 85% at the optimal points. It can be concluded that CBME system can be a suitable alternative for removal of recalcitrant carbon and color post-biological treatment in distillery wastewaters.