Biogranular sludge for rubber processing wastewater in a sequencing batch reactor

Rubber is one of the major agro-based industrial sectors that contributes to the development of the country. Malaysia is one of the leading producers of natural rubber in the world. The rubber industry consumes large volume of water, uses chemicals and other utilities, and produces an enormous amount of wastes and effluent. As rubber effluent contributes to highly polluted wastewater, the need to find an efficient and practical approach to preserve the environment is essential. Thus, this study aims to investigate the applicability of aerobic granular sludge technology in treating rubber processing wastewater using a laboratory scale sequencing batch reactor (SBR) system. Aerobic granular sludge was developed in a 1.6 L working volume of column reactor that operated with 3 hours of cycle time for 90 days. The reactor had a volumetric exchange ratio of 30% and the superficial upflow air velocity was set at 1.2 cm/s. The dissolved oxygen in the reactor was within the range of 6.0-7.5 mg/L. The SBR system was run at organic loading rate of 0.8-3.3 kg COD/m3 day and COD/N/P ratio was 100/19/8. Results showed that aerobic granules formed had an average diameter of 1.4 to 2.8 mm with settling velocity of 57.8 ± 3.5 m/h and sludge volume index (SVI) of 46.0 mL/g. These properties caused a significant increase in biomass concentration from 3.8 to 10.1 g/L, which was observed to be beneficial for the performance of the reactor system. The scanning electron microscope (SEM) examinations revealed that aerobic granular sludge consisted of non-filamentous cocci-shaped bacteria, tightly linked to one another to form a compact structure. The performances of aerobic granules that formed at three different cycle times of 3, 6 and 12 hours of SBR operation were studied. The highest cycle time favours the highest removal performances in removing organic and nutrients. 96.9% COD removal was achieved when the reactor was operated at high cycle time of 12 hours, while around 60.0% and 65.9% removal efficiencies were recorded for total nitrogen and total phosphorus in the granular SBR system for rubber processing wastewater treatment. The metagenome analysis was used to discover the microbial community that accumulated in aerobic granular sludge, which was potential in the granulation and biodegradation process. The abundance of COD degrading, denitrifying and polyphosphate bacteria such as Pseudomonas, Agrobacterium and Thauera bacteria were high in aerobic granules. Those bacteria had both capability in producing extracellular polymeric substances (EPS) and degrading waste. The characteristics of EPS of aerobic granular sludge were determined. Proteins (PN) were more dominant than polysaccharides (PS) in the EPS of aerobic granular sludge. The excitation-emission matrix (EEM) results also indicated the importance of aromatic protein-like substances, particularly tryptophan in maintaining the stable structure of granular sludge. Despite the different cycle times, aerobic granular sludge formation was successfully achieved for the treatment of high strength wastewater such as rubber effluent

Efficiency of aerobic granulation technology in treating high strength soy sauce wastewater

The present study investigated the efficiency of aerobic granular sludge (AGS) technology in treating effluent from soy sauce industry which is categorized as a high strength wastewater. The combination of anaerobic and aerobic granulation technology in SBR system was used in this study which was efficiently treated COD from the soy sauce wastewater where 87% of removal was achieved. Ammonia and colour was removed at a maximum of 87 and 76%, respectively, in the SBR system. Matured, dense and compact granules with 2.5 mm in diameters were developed with a good settling velocity (45 m/h) and 28 mL/gSS of sludge volume index (SVI). Hence, AGS technology was proven as an excellent treatment for soy sauce wastewater for being discharge into the environment, as the effluent was treated in one biological reactor with high hydraulic and organic loadings besides less production of sludge. In this study, the capabilities of AGS technology in treating relatively higher concentration of organic impurities present in the soy sauce wastewater were demonstrate

Performance of aerobic granular sludge at variable circulation rate in anaerobic–aerobic conditions

Aerobic granular sludge (AGS) has been applied to treat a broad range of industrial and municipal wastewater. AGS can be developed in a sequencing batch reactor (SBR) with alternating anaerobic– aerobic conditions. To provide anaerobic conditions, the mixed liquor is allowed to circulate in the reactor without air supply. The circulation flow rate of mixed liquor in anaerobic condition is the most important parameter of operation in the anaerobic-AGS processes. Therefore, this study investigates the effect of circulation rate on the performance of the SBR with AGS. Two identical reactors namely R1 and R2 were operated using fermented soy sauce wastewater at circulation rate of 14.4 and 36.0 l/h, respectively. During the anaerobic conditions, the wastewater was pumped out from the upper part of the reactor and circulated back into the bottom of the reactor for 230 min. A compact and dense AGS was observed in both reactors with a similar diameter of 2.0 mm in average, although different circulation rates were adopted. The best reactor performance was achieved in R2 with chemical oxygen demand removal rate of 89%, 90% total phosphorus removal, 79% ammonia removal, 10.1 g/l of mixed liquor suspended solids and a sludge volume index of 25 ml/g

Livestock wastewater treatment using aerobic granular sludge

The present study demonstrated that aerobic granular sludge is capable of treating livestock wastewater from a cattle farm in a sequencing batch reactor (SBR) without the presence of support material. A lab scale SBR was operated for 80 d using 4 h cycle time with an organic loading rate (OLR) of 9 kg COD m3 - d1 . Results showed that the aerobic granules were growing from 0.1 to 4.1 mm towards the end of the experimental period. The sludge volume index (SVI) was 42 ml g1 while the biomass concentration in the reactor grew up to 10.3 g L1 represent excellent biomass separation and good settling ability of the granules. During this period, maximum COD, TN and TP removal efficiencies (74%, 73% and 70%, respectively) were observed in the SBR system, confirming high microbial activity in the SBR system

Characteristics and performance of aerobic granular sludge treating rubber wastewater at different hydraulic retention time

The influence of hydraulic retention time (HRT, 24, 12, and 6h) on the physical characteristics of granules and performance of a sequencing batch reactor (SBR) treating rubber wastewater was investigated. Results showed larger granular sludge formation at HRT of 6h with a mean size of 2.0±0.1mm, sludge volume index of 20.1mLg-1, settling velocity of 61mh-1, density of 78.2gL-1 and integrity coefficient of 9.54. Scanning electron microscope analyses revealed different morphology of microorganisms and structural features of granules when operated at various HRT. The results also demonstrated that up to 98.4% COD reduction was achieved when the reactor was operated at low HRT (6h). Around 92.7% and 89.5% removal efficiency was noted for ammonia and total nitrogen in the granular SBR system during the treatment of rubber wastewater

Performance of aerobic granular sludge in treating soy sauce wastewater at different hydraulic retention time

Aerobic granular sludge had shown its capability in treating soy sauce wastewater, but its reactor performance, granules properties and biokinetics in different hydraulic retention times (HRT) is still unknown. To ensure the reactor is performed in optimum condition, a judicially selection of HRT is important. The study was conducted in a high and slender column operated according to a sequential batch reactor (SBR) with a sequence of aerobic and anaerobic/anoxic reaction phases. Three different HRTs (8, 16, 24 h) and different anaerobic and aerobic reaction time were evaluated. In the study demonstrated the increase in HRT could reduce the organic loading rate (OLR) as well as biomass yield (Yobs, Y), endogenous decay rate (kd) and overall specific biomass growth rate (µoverall). It was observed a slight increase in the mixed liquor suspended solid (MLSS) and the granules mean size as the OLR decreased. Meanwhile, in the lowest HRT reactor, a narrow diameter range of aerobic granule from 3 to 100 µm was observed due to the development of small and dense granules. The HRT of 24h with aerobic and anaerobic/anoxic reaction time of 3.88 and 7.77h respectively is the SBR’s best performances due to the improvement of the aerobic granular physical propertie

Cultivation of aerobic granular sludge for rubber wastewater treatment

Aerobic granular sludge (AGS) was successfully cultivated at 27 ± 1 C and pH 7.0 ± 1 during the treatment of rubber wastewater using a sequential batch reactor system mode with complete cycle time of 3 h. Results showed aerobic granular sludge had an excellent settling ability and exhibited exceptional performance in the organics and nutrients removal from rubber wastewater. Regular, dense and fast settling granule (average diameter, 1.5 mm; settling velocity, 33 m h1 ; and sludge volume index, 22.3 mL g1 ) were developed in a single reactor. In addition, 96.5% COD removal efficiency was observed in the system at the end of the granulation period, while its ammonia and total nitrogen removal efficiencies were up to 94.7% and 89.4%, respectively. The study demonstrated the capabilities of AGS development in a single, high and slender column type-bioreactor for the treatment of rubber wastewate