Natural-Based Sustainable Filter Media for Ammonia and TSS Removal in Small-Scale Aquaculture

We studied the effect of sand filtration with natural esker material on the removal of total organic carbon (TOC), total suspended solids (TSS), and turbidity from the effluent of an experimental recirculating aquaculture system (RAS) farm. Separate experiments were performed with the same esker sand: (1) a soil column experiment in 2017 where the effluent (mean TOC 8.14 mg L−1) was percolated vertically through a 50-cm-thick sand column with the infiltration 1 m day−1; (2) a sand filtration experiment with water-saturated conditions in 2018 where the effluent from the woodchip denitrification (mean TOC 26.84 mg L−1) was infiltrated through a sand layer with the retention time of 1.2 days. In experiment 2, infiltration of 25 L day−1 through a 31-cm sand layer and 40 L day−1 through a 50-cm sand layer were studied. Both experiments were performed in association with rainbow trout (Oncorhynchus mykiss) grow-out trials. In sand filtration with vertical water flow through a soil column, the removal of TSS was 40%, while of TOC 6%, partly due to the small thickness of the soil column and coarse sand material. In water-saturated conditions, mean removal of TOC (3 mg L−1 1.2 day−1), TSS (1.2 mg L−1 1.2 day−1), and turbidity (0.4 FTU 1.2 day−1) reached 11% (TOC), 18% (TSS), and 15% (turbidity), even with the retention time of only 1.2 days. The removal of TOC in water-saturated conditions correlated with the removal of TSS and turbidity.

Aquaculture wastewater often contains high levels of suspended solids and turbidity, which may negatively affect water quality and aquatic ecosystems if discharged without treatment. Although chemical coagulants are effective for suspended solids removal, their use is associated with environmental, economic, and sludge management concerns. However, limited studies have explored the use of sago waste as a natural coagulant for aquaculture wastewater treatment, particularly for turbidity and total suspended solids (TSS) removal. This study investigates the effectiveness of sago waste as a natural coagulant for aquaculture wastewater treatment and examines the effect of coagulant dosage on turbidity and TSS removal. Jar test experiments were conducted using aquaculture wastewater treated with sago waste at dosages ranging from 0.1 to 10 mg/L. Turbidity and TSS concentrations were measured before and after treatment to determine removal efficiency. The results showed that sago waste was able to reduce turbidity and TSS at all tested dosages. Turbidity removal efficiency increased from 16.97% at 0.1 mg/L to a maximum of 20.50% at 10 mg/L, indicating the optimal dosage for turbidity removal at 10 mg/L, while TSS removal showed limited variation, with the optimal dosage observed at 1 mg/L, achieving a removal efficiency of 13.86%. In conclusion, sago waste demonstrated greater effectiveness in turbidity reduction than in TSS removal and can serve as a sustainable and low-cost natural coagulant for preliminary treatment of aquaculture wastewater.

Use of vegetated drainage ditches and low-grade weirs for aquaculture effluent mitigation: II. Suspended sediment

This study aimed to evaluate the performance of combined constructed wetland systems (vertical – horizontal flow) in removing organic matter, cultivated with Tifton 85 grass (Cynodon spp.) and cattail (Typha sp.), using pretreated swine wastewater (from anaerobic systems) at variable loading rates. The experimental system was composed of six constructed flooded systems. The flow was frequently monitored by direct measurement, and subsequently, the pH, influent, and effluent concentrations of the variables total solids (TS) and total suspended solids (TSS) and chemical oxygen demand (COD) were determined. The results showed that the average removal of total solids (TS) and total suspended solids (TSS) did not change significantly (p > 0.05) with increasing applied load in vertical flooded systems. While statistically significant differences (p < 0.05) were observed for ST in VFCW3 in Phase III (801–540 mg.L−1, 33%) and for TSS in VFCW2, which showed 48% removal in Phase III (122–62 mg.L−1, 48%), indicating that specific configurations can improve system efficiency. On the other hand, the average removal of total suspended solids (TSS) did not change significantly (p > 0.05) with increasing applied load in horizontal flooded systems. However, the average removal of total suspended solids (TSS) increased significantly (p < 0.05) with increasing applied load in horizontal flooded systems. Therefore, it can be concluded that the COD removal efficiencies, in general, increased with the increase in the applied organic load, reaching approximately 50% (307–271 mg.L−1 VFC3 and 307–145 mg.L−1 HFCW3) for the VFCW‐HFCW set.

In wastewater treatment, two issues have recently received increased attention: nature-based solutions for addressing urban water stress through decentralized treatment and re-use; and emerging pollutants such as microplastics (MPs). At the interface of these, this study investigated living green walls for greywater treatment and their potential for MP removal.A large, pilot-scale green wall was irrigated with greywater (a mix of water collected from laundry, dishwasher, bathroom sinks, and synthetic greywater), and effluent from planted and unplanted sections was compared. MPs >50 μm were analyzed using μRaman spectroscopy and supplementary fluorescence microscopy imaging. The green wall proved efficient for the reduction of chemical oxygen demand (COD) (around 80%), removal of total suspended solids (TSS) (around 90%) and MPs, especially for MPs of the non-polar, hydrophobic polymer type polystyrene and MPs sized 100–500 μm. MP removal was improved in the planted (50–60%) compared to the unplanted section (20%), especially for the size fraction 100–500 μm. Physical filtration by the green wall growing media (a mix of perlite with a grain size of 1–5 mm, and coconut fiber), which was further enhanced by plant roots decreasing the effective pore size, can be considered the most important removal mechanism. Charge-mediated adsorption cannot be expected as MPs and growing media mix were both negatively charged at the prevailing water pH (7–8). Fluorescence imaging for MP analysis, using a merged UV/blue light fluorograph, overestimated MP concentrations in greywater (hundreds of MPs per sample were identified by fluorescence imaging versus tens of MPs by μRaman spectroscopy) and would benefit from further improvement before it can be reliably applied as a cheaper and faster alternative methodology for MP analysis.

Optimization of coagulation–flocculation process for pulp and paper mill effluent by response surface methodological analysis

Effluent from palm oil mill processing is a major concern due its properties and characteristics that highly contributed to water pollution. This study reported on POME treatment by a semi-continuous treatment system consisting of coagulation, sedimentation and filtration processes in the presence of a by-product coagulant (copperas combined with lime). The treatment was conducted for different types of filter medias (FMs): a) FM 1: sand+activated carbon and b) FM 2: sand+ceramic ring) and various retention times (RT) from 1/2 to 2 h. The treatment resulted in different removal efficiencies of turbidity, colour, chemical oxygen demand (COD) and total suspended solids (TSS) for secondary and tertiary POME samples. With semi-continuous treatment, the pollutants in the secondary POME sample decreased, resulting in the removal efficiency of 57.34% for turbidity, 95.16% for colour, 82.08% for COD and 83.23% for TSS. Meanwhile, the results of the tertiary sample were 54.81%, 81.08%, 78.05% and 68.51% for turbidity, colour, COD and TSS removal respectively. The statistical analysis of ANOVA (p-value<0.05) indicated that the data was statistically significant with the FM 1 as a media filter. As a result, a semi-continous chemical-physical treatment system may provide information in efficient POME treatment.

ABSTRACTA modified anaerobic baffled reactor (ABR) combined with a submerged membrane bioreactor (MBR) was applied to treat municipal wastewater. The performance of this process was examined in terms of the removal of organic matter, suspended solids, turbidity and nitrogen. The raw wastewater was fed to the 105 L ABR and then the treated effluent was driven to a 58 L MBR equipped with a submerged hollow fibre ultrafiltration membrane module. The integrated modified ABR–MBR process resulted in the complete removal of total suspended solids (TSS) and in very high chemical oxygen demand (COD) removal (93.3 ± 3.8%). Furthermore, the recycling of mixed liquor from the MBR to the modified ABR resulted in some denitrification occurring in the first compartment of the ABR, resulting in 53 ± 6% removal of nitrogen by the integrated process. The membrane flux was stable and above 20 L/m2h. Membrane examination at the nanoscale indicated the deposition of small particles on the surface of the membranes.

A coagulation-flocculation (CF) process using aluminum sulfate as a coagulant was employed to treat highly suspended solids in tunnel wastewater. Response surface methodology (RSM) based on a Box-Behnken design was applied to evaluate the effects of three factors (coagulant dosage, pH and temperature) on total suspended solids (TSS) removal efficiency as well as to identify optimal values of those factors to maximize removal of TSS. Optimal conditions of coagulant dosage and pH for maximum TSS removal changed depending on the temperature (). As temperature increased, the amount of coagulant dosage and pH level decreased for maximum TSS removal efficiency during the CF process. Proper adjustment of optimal pH and coagulant dosage to accommodate temperature fluctuations can improve TSS removal performance of the CF process.

Resilience and reliability of compact vertical-flow treatment wetlands designed for tropical climates

Sago is a carbohydrate-producing plant that is widely found in Papua. The main product of sago plant processing is sago starch which in the extraction process is carried out with the help of water media. Water that has been used in the extraction process of sago starch is generally only disposed of as waste that is not useful, even potentially polluting the environment. Therefore, to improve the quality of liquid waste, filtration needs to be carried out. This study aims to see the effect of several types of filtration media on the quality of sago extraction wastewater. In this study three types of filtration media were used, namely sand (P), coconut fiber (S) and coconut shell charcoal (A) and a combination of sand and coconut fiber (PS), sand and coconut shell charcoal (PA), coconut fibers and charcoal coconut shell (SA). The parameters of the quality of the sago extraction wastewater were observed in total suspended solids (TSS), total dissolved solids (TDS), pH, temperature, odor, and color. The results showed that coconut shell charcoal filtration media was better than the other two types in decreasing TSS and TDS by 17% and 24% respectively. However, if the filtration media was combined, it will produce a better quality of wastewater compared to a single filtration medium (without combination) for all observation parameters. An increase in pH and odorless happened for the wastewater after filtration in all treatments

A constructed wetland system for bio-polishing palm oil mill effluent and its future research opportunities

With the economic upsurge and continuous industrial development of Southeast Asia’s palm oil sector, Malaysia alone produced an estimated 19 million tonnes of crude palm oil (CPO) in 2015. However, CPO production is in tandem with the high generations of both solid waste and effluent. Environmental issues related to the wellbeing of watercourses became a concern due to the discharge of palm oil mill effluent (POME). Governmental and international bodies have acknowledged the need to develop and implement sustainable effluent management strategies, especially concerns relating to the implementation of suitable treatment technologies with realistic pricing. Noted for its potential to treat organically polluted water and wastewater in major water utilities, coagulation and flocculation treatment using natural polymers can be an ecological and environmentally-friendly alternative to treat POME. In this study, the feasibility of applying natural seed gum and its derivative was investigated to treat POME by means of coagulation and flocculation processes as a sustainable alternative to ponding systems. <br> <br> The works which were conducted in the initial stage of research (Chapters 3 and 4) established and optimized the treatment of POME via coagulation-flocculation process using natural Cassia obtusifolia seed gum. Chapter 3 investigated the potential of C. obtusifolia seed gum as a natural coagulant in comparison with aluminium sulphate (alum) in treatment of POME. A series of batch experiments were performed under various factors: wastewater concentration, dosage of coagulant, initial pH of wastewater, settling time, slow stirring speed, and temperature. The removal of total suspended solids (TSS) and chemical oxygen demand (COD) were measured and used to assess the treatment efficiency. The findings of this study highlighted the negligible effect of wastewater temperature on the treatment efficiency when C. obtusifolia seed gum was used in comparison with alum. Based on the results, the recommended conditions to treat POME (TSS: 7500 mg/L) using C. obtusifolia seed gum were dosage, initial pH, and settling time of 1.0 g/L, pH 3, and 45 min, respectively. These treatment conditions enabled removals of TSS and COD up to 87 and 55%, respectively. After determining the key effects of the treatment process in Chapter 3, the influence of coagulant dosage and settling time on TSS and COD removals were optimized via response surface methodology. The treatment of POME using C. obtusifolia seed gum showed higher TSS (93.9%) and COD (61.2%) removals after undergoing optimization. In addition, the combined treatment using alum plus C. obtusifolia seed gum was examined and optimized to explore its synergistic effect on treatment of POME at natural pH (pH 4.8 – 5.0). The combined treatment using alum plus C. obtusifolia seed gum yielded high TSS and COD removals up to 81.58 and 48.22%, respectively using the following optimum conditions: alum dosage of 1.15 g/L, C. obtusifolia seed gum dosage of 2.47 g/L, and settling time of 35.16 min. <br> <br> To further improve the potential application of C. obtusifolia seed gum in the treatment of POME, a new derivative of the natural seed gum was developed in the following study (Chapter 5). Since POME contains countless colloidal particles which are negatively charged, the study was aimed towards developing a cationic C. obtusifolia seed gum with enhanced treatment capability. The natural seed gum was modified through an etherification process which leads to the substitution of reactive hydroxyl groups with cationic moieties from N-(3-chloro-2-hydroxypropyl) trimethyl ammonium chloride (CHPTAC). The influence of cationic monomer concentration, catalyst concentration, reaction temperature, and reaction time were studied for the synthesis based on TSS and COD removals. The study showed that cationic C. obtusifolia seed gum, which was synthesized (at 50 °C and 5 h) using 19×10-3 mol of CHPTAC and 6×10-2 mol of sodium hydroxide (NaOH), removed 87% of TSS and 52% of COD from the POME. C. obtusifolia seed gum exhibited enhanced viscosity, higher magnitude of zeta potential (+6.41 mV) and changes in composition, thermal behaviour, and surface morphology after undergoing etherification. <br> <br> The final stage of this research (Chapter 6) optimized the treatment of POME using cationic C. obtusifolia seed gum. In addition, an integrated approach was investigated by employing ultrasonic technology to further assist coagulation-flocculation treatment of POME. The first stage of optimized coagulation-flocculation treatment required 0.4 g/L of cationic seed gum and 48 min of settling time. The performance of a subsequent coagulation-flocculation treatment using 0.22 g/L of cationic seed gum and 49 min of settling time was enhanced by the introduction of an ultrasound treatment lasting for 47 min at intensity of 49% prior to the subsequent treatment. Ultrasonic irradiation was found to improve subsequent coagulation-flocculation treatment by 27 and 3% in TSS and COD removals in comparison with unassisted and continuous coagulation-flocculation treatment. The overall study demonstrated the simple and effective use of modified natural polymers and ultrasonic-assisted coagulation-flocculation treatment systems to facilitate solid-liquid separation of POME.

High-flow media (HFM) are able to treat large runoff volumes using small-footprint systems. Four full-scale HFM stormwater control measures (SCMs) in a residential area were monitored over 11 months to assess the removal of total suspended solids (TSS), nitrogen, and phosphorus in first-flush (FF) stormwater runoff. Excellent removal of TSS and particulate-bound nutrients is noted, but, in most SCMs, removal of dissolved species is limited. Sorption of dissolved P occurs, although most likely on captured sediment and not on the HFM itself. N removal varies among the systems, but, in general, mineralization and nitrification of accumulated N species in the SCMs leads to nitrate export. FF is present in TSS (strongest), total nitrogen, and total phosphorous (weakest). HFM grain size and organic content do not significantly impact TSS or P removal, but higher organic content is associated with higher N removal. Optimal HFM SCM design incorporates sedimentation before filtration to minimize clogging concerns.

A 20L attachedgrowth anaerobic system with floating plastic Ballast rings as a medium has been studied forswine wastewater [chemical oxygen demand (COD) = 1,925 to 2,033 mg/L; total suspended solids (TSS) = 1,051 to 1,184mg/L] treatment at the mesophilic temperature of 35C. The plastic Ballast rings had a specific surface area of 108 m 2 /m 3and a density of 0.98 g/cm 3 and filled the upper half of the anaerobic digesters. The porosity of the filled portion of the digesterswas 0.86. Performance of the anaerobic digesters was evaluated for organics decomposition and methane production withtwo different hydraulic retention times (HRTs): 10 days and 5 days. When HRT was 10 days in the anaerobic digesters, removalof COD, total organic carbon (TOC), TSS, and volatile suspended solids (VSS) was 65%, 55%, 69%, and 70%, respectively.Methane yield was 0.23 m 3 CH4 per kg COD removed. As the HRT was reduced to 5 days, the removal of COD, TOC, TSS,and VSS decreased to 55%, 48%, 57%, and 60%, respectively. Methane yield was 0.24 m 3 CH4/kg CODrem. Higher HRT inthe anaerobic digester resulted in higher organics degradation efficiency. However, higher rates of methane production andorganics decomposition were obtained in the digester with lower HRT.