Response of algal-bacterial granular system to low carbon wastewater: Focus on granular stability, nutrients removal and accumulation

Abstract

The effect of influent chemical oxygen demand to nitrogen (COD/N) ratio on the granular stability, nutrients removal and accumulation of the algal-bacterial AGS was investigated. Two sequencing batch reactors were operated under different influent COD/N ratio, i.e., R (control, COD/N = 8) and R: (COD/N = 8, 4, 2, and 1 through stepwise decrease of COD). Results showed that the integrity coefficient of the granules in R stabilized at 0.7-5.4% during the whole operation. Significantly enhanced dissolved inorganic carbon (DIC) uptake and the faster growth of algae indicated the great potential for reduction in greenhouse gases (GHGs) emission by using the algal-bacterial AGS system. The algal-bacterial AGS biomass contained high phosphorus (P) and N contents as well as extremely high P bioavailability (up to 98%) which could be easily used for resource recovery. Loosely bound extracellular polymeric substances (LB-EPS) might be the key factor to control the deterioration of granular stability in this system.

Stability and performance of algal-bacterial granular sludge in shaking photo-sequencing batch reactors with special focus on phosphorus accumulation

“…Prior to the experiments, mature algal-bacterial AGS was cultivated in the laboratory-scale sequencing batch reactor (SBR) which has been operated stably for more than 3 months. The dominant algae species, Leptolyngbya, was the same as that in Zhao et al (2018). The initial concentration of mixed liquor volatile suspended solids (MLVSS) was around 3.87±0.03 g/L in each photoreactor.…”

“…Synthetic wastewater used in this work was the same as the influent to R1 in a previous study (Zhao et al, 2018), which was mainly characterized as 400 mg COD/L, 50 mg NH4 + -N/L, and 10 mg PO4 3--P/L to mimic the domestic wastewater in China.…”

“…All the analytical methods were described elsewhere (Zhao et al, 2018), including the quantification and characterization of granular biomass (ML(V)SS, SVI, chlorophyll a, granular size and distribution, granular strength, P fractionation in biomass), water quality (total nitrogen (TN), ammonia nitrogen (NH4 + -N), nitrite nitrogen (NO2 --N), nitrate nitrogen (NO3 --N), phosphorus (PO4 3--P), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), dissolved total carbon (DTC)), and extracellular polymeric substances (EPS) extraction and determination.…”

“…In addition, algal biomass produced from wastewater treatment can serve as P fertilizer in agriculture (Mulbry et al, 2005). A recent research (Zhao et al, 2018) reported that high P content (2.8-3.0%) with extremely high P bioavailability (up to 98%) could be achieved in the algal-bacterial AGS treating low influent carbon wastewater, which is easily used for P resource recovery. Besides, loss of granular stability during the long-term operation is a major concern for practical application of this promising biotechnology.…”

Algal-Bacterial Symbiosis System Treating High-Load Printing and Dyeing Wastewater in Continuous-Flow Reactors under Natural Light

“…Third, most research has presently limited to low-load wastewater for a single ABS system at present. Zhao et al [12] studied the stability of algal-bacterial granular system using low carbon wastewater of COD (200 mg/L): N(50 mg/L) = 4:1, COD (100 mg/L): N (50 mg/L) = 2:1 and COD (50 mg/L): N (50 mg/L) = 1:1. Fourth, most of these studies were conducted in sequential batch reactors (SBR) reactors [10,13].…”