Impact of carrier on ammonia and organics removal from zero-discharge marine recirculating aquaculture system with sequencing batch biofilm reactor (SBBR)

A review on algal-bacterial symbiosis system for aquaculture tail water treatment

Aquaculture is one of the fastest growing fields of global food production industry in recent years. To maintain the ecological health of aquaculture water body and the sustainable development of aquaculture industry, the treatment of aquaculture tail water (ATW) is becoming an indispensable task. This paper discussed the demand of environmentally friendly and cost-effective technologies for ATW treatment and the potential of algal-bacterial symbiosis system (ABSS) in ATW treatment. The characteristics of ABSS based technology for ATW treatment were analyzed, such as energy consumption, greenhouse gas emission, environmental adaptability and the possibility of removal or recovery of carbon, nitrogen and phosphorus as resource simultaneously. Based on the principle of ABSS, this paper introduced the key environmental factors that should be paid attention to in the establishment of ABSS, and then summarized the species of algae, bacteria and the proportion of algae and bacteria commonly used in the establishment of ABSS. Finally, the reactor technologies and the relevant research gaps in the establishment of ABSS were reviewed and discussed.

Upgrading sequencing batch reactor using attached biofilm

A conventional sequencing batch reactor (SBR) was upgraded using fixed biofilm carriers with a specific surface area around 18 m² m^-3 . The upgraded SBR was investigated to remove phenol from high strength wastewater operated under various operational conditions. The operational conditions used were variable volume exchange ratio (VER) up to 75%, hydraulic retention time (HRT) from (10.7-21.3 hr), aeration time (from 2 to 8 hr), and initial phenol concentration up to 600 mg L^-1 . It was found that the upgraded SBR increased the removal efficiencies of biological oxygen demand (BOD₅ ), chemical oxygen demand (COD), and total suspended solids (TSS) by about 10% using high strength wastewater without phenol compared to SBR. Furthermore, the removal rate of phenol for the upgraded SBR was higher than conventional SBR by about 18% at 600 mg L^- of initial phenol concentration under the same operational conditions. Compared to the conventional SBR, the upgraded version reduced the aeration step by 25% and achieved higher removal efficiency of phenol. Moreover, it reduced the excess sludge by about 23% and enhanced its properties by lowering the sludge volume index (SVI) by about 33%. PRACTITIONER POINTS: Upgrading conventional SBR by adding biofilm carriers is necessary for wastewater treatment with high strength wastewater. The upgraded SBR has a higher resistance toward phenol compound due to the presence of the attached biofilm. The upgraded SBR enhances sludge settling properties, decreases the amount of excess sludge, and also reduces the start-up period. The number of cycles per day by upgraded SBR was more than the conventional SBR by 15%. The upgraded SBR is an effective system and has good operational stability.

Study on COD and nitrogen removal efficiency of domestic sewage by hybrid carrier biofilm reactor

A moving bed biofilm reactor (MBBR) is a kind of commonly used biological sewage treatment process. A carrier, the core of MBBR, could directly affect the treatment efficiency of MBBR. In this experiment, a hybrid carrier composed of an MBBR carrier and fluidized bed porous carrier was innovatively utilized to treat low-concentration simulated domestic sewage through an MBBR reactor to investigate the effects of different hydraulic retention times (HRT) and different carrier dose ratios on the reactor performance. The results indicated that when the volume ratio of the carrier dosage was 5% : 20% when the reactor HRT was 5 h, the removal rates of ammonia nitrogen, total nitrogen (TN) and chemical oxygen demand (COD_Cr) were optimal, which were 96.5%, 60.9% and 91.5%, respectively. The ammonia nitrogen, total nitrogen and COD_Cr concentrations of the effluent were 1.04 mg L⁻¹, 12.20 mg L⁻¹ and 29.02 mg L⁻¹, respectively. Furthermore, the total biomass concentration in the hybrid carrier biofilm reactor (HCBR) was 3790.35 mg L⁻¹, which also reached the highest value. As the experiment progressed, the concentrations of protein, polysaccharide and soluble microbial products (SMP) were reduced to 7.68 mg L⁻¹, 11.10 mg L⁻¹ and 18.08 mg L⁻¹, respectively. This was basically consistent with the results of the three-dimensional fluorescence spectrum. The results showed that the combined-carrier biofilm reactor could reduce the volumetric filling rate, improving the removal capability of organic matter and the denitrification efficiency. This study provided technical support for the composite carrier biofilm wastewater treatment technology, and also had a good prospect of application.

A combined-carrier biofilm reactor could reduce the volumetric filling rate, improving the removal capability of organic matter and the denitrification efficiency.

Study of Humic Acid Adsorption Character on Natural Maifan Stone: Characterization, Kinetics, Adsorption Isotherm, and Thermodynamics

In this paper, the adsorption of humic acid (HA) on natural maifan stone (MS) in aqueous medium was investigated. The changes in MS after adsorption have been characterized explicitly. The adsorption behavior was studied by varying the factors of pH (5-10), reaction time (10-180 min), initial HA concentration (5-50 mg/L), adsorbent dosage (0.1-1.2 g), and temperature (25-45 °C). The kinetics of the adsorption process of HA was fitted well with the pseudo-second-order model (R ² = 0.99). The isothermal results revealed that the adsorption process is favorable, and highly fitting Langmuir models (R ² > 0.99) were used. Additionally, the obtained maximum adsorption capacity of MS for HA was approximately 1 mg/g. The adsorption process of HA onto MS was endothermic according to the thermodynamic study. The changes in the excitation-emission-matrix of HA and the X-ray diffraction of MS after adsorption indicate the interaction of HA and MS. However, the reason for these changes is still unclear. Thus, the results show that the natural MS exhibited a certain adsorption capacity for HA. It is promising to develop novel natural MS-based materials for adsorption of HA.