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The transformation characteristics of carbon, nitrogen, phosphorus and sulfur in dewatering sludge from municipal wastewater treatment plant (WWTP) were investigated after thermal hydrolysis pretreatment at 165 degress C for 50 min. The results showed that the hydrolysis efficiency of VSS could reach as high as 43.35%, 54.36% of protein and 65.12% of carbohydrate were transferred to dissolved organics, respectively, and the main component of dissolved organic matter in hydrolysate was dissolved protein (52.18% ), 54.23% of insoluble organic nitrogen was turned into dissolved nitrogen and 22.13% of dissolved nitrogen in hydrolysate was converted to ammonia. The transformation rate of insoluble phosphorus was 30.52%. Dissolved phosphorus was mostly transformed to phosphate (79.84%) as phosphorus-accumulating bacteria cells were crushed. 50.03% of insoluble organic sulfur was hydrolyzed, and little change was detected in sulfide (0.50%). The analysis results of the organic compounds transformation are valuable for treatment of the thermal hydrolysis pretreated sludge with high solid content.

The uncontrolled release of nutrients from waste sludge results in nitrogen and phosphorus overloading in wastewater treatment plants when supernatant is returned to the inlet. A controlled release, recovery and removal of nutrient from the waste sludge of a Biological Nutrient Removal system (BNR) are investigated. Results showed that the supernatant was of high mineral salt, high electrical conductivity and poor biodegradability, in addition to high nitrogen and phosphorus concentrations after the waste sludge was hydrolysed through sodium dodecyl sulphate addition. Subsequently, over 91.8% of phosphorus and 10.5% of nitrogen in the supernatants were extracted by the crystallization method under the conditions of 9.5 pH and 400 rpm. The precipitate was mainly struvite according to X-ray diffraction and morphological examination. A multistage anoxic-oxic Moving Bed Biofilm Reactor (MBBR) was then adopted to remove the residual carbon, nitrogen and phosphorus in the supernatant. The MBBR exhibited good performance in simultaneously removing carbon, nitrogen and phosphorus under a short aeration time, which accounted for 31.25% of a cycle. Fluorescence in situ hybridization analysis demonstrated that nitrifiers presented mainly in floc, although higher extracellular polymeric substance content, especially DNA, appeared in the biofilm. Thus, a combination of hydrolysis and precipitation, followed by the MBBR, can complete the nutrient release from the waste sludge of a BNR system, recovers nutrients from the hydrolysed liquor and removes nutrients from leftovers effectively.

Since the notable amount of particulate substrate in wastewater, the implications of particulate substrate on treatment efficiency have been a topic of major interest in the field of biological wastewater treatment. The particulate substrate has to be hydrolyzed by the extracellular enzymes, which are mainly embedded in extracellular polymeric substances (EPS) matrix of microbial aggregates, prior to consumption. Therefore, the important relevance between the particulate substrate and the characteristics of EPS can be expected. In this study, two lab-scale sequencing batch reactors were performed in parallel to investigate the effects of particulate and soluble substrate on the physicochemical characteristics of EPS in activated sludge. The results showed that the particulate substrate in the influent could significantly change the properties of activated sludge and the characteristics of EPS. More open and fluffy flocs with poorer settleability and dewaterability were formed with particulate substrate. More protein and humic compounds were introduced into the EPS matrix due to the deep involvement of protein and humic compounds in hydrolysis process of particulate substrate. The increments of protein and humic compounds then caused the slight higher molecular weight, higher hydrophobicity and lower zeta potential of EPS in particulate substrate system. The results in this study permitted for obtaining answers to understand the significant implications of particulate substrate in determining the physicochemical characteristics of EPS in biological wastewater treatment systems., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Phosphorous removal & denitrifying phosphate uptake of the granular sludge was investigated in this study. Inoculated with flocculation sludge, the granulation of the biological phosphorous removal sludge was realized in a sequencing batch reactor (SBR) fed with sodium acetate by means of hydraulic selection under an anaerobic/oxic alternating operation (referred to as an A/O). Then the biological phosphorous removal granular sludge was induced into the denitrifying phosphate uptake granular sludge under an anaerobic/anoxic/oxic alternating operation (referred to as an A/A/O). The properties of the two kinds of granular sludge were studied. The biological phosphorus removal granular sludge was completed on the 82nd day. The biological phosphorus removal granule sludge showed some characteristics, e.g. pallideflavens in color, 0.5-1.5 mm in diameter, 20-30 m/h in settling velocity, 94% in water content, 1.043 9 in specific gravity, and below 50 mL/g in SVI. The max. specific release phosphorus rate (SRPR), the max. specific uptake phosphorus rate (SUPR) and the phosphorus content of the MLSS (TP/SS) was 67.7 mg/(g x h), 43.2 mg/(g x h) and 6.5% respectively on the 437th day. On the 448th day the operation of the reactor was changed into A/A/O. The max. SRPR, the max. anoxic SUPR and the TP/SS of the denitrifying phosphate uptake granular sludge was 30 mg/(g x h), 27.9 mg/(g x h) and 6.3% respectively on the 653rd day. The two kinds of granular sludge had potential to carry out phosphorus removal.

The community of nitrifiers cultivated with reject water were investigated by fluorescent in situ hybridization (FISH) performed with 16S rRNA-targeted oligonucleotide probes, and the kinetic properties such as temperature correction factor tauN and the half saturation coefficient K(N) were also investigated. The results showed that the percentage of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in the activated sludge was 15.7% +/- 3.7% and 12.9% +/- 3.2%, Nitrosomonas europaea-Nitrosococcus mobilis lineage were the dominant AOB, Nitrobacter spp. were the dominant NOB. The temperature correction factors of ammonium utilized rate (AUR) and nitrite utilized rate (NUR) were 1.092 and 1.061 respectively; the K(N) of AOB and NOB were (1.60 +/- 0.29) mg/L (NH4(+) -N), (2.78 +/- 0.30) mg/L (NO2(-) -N) respectively.

Substrate utilization in a glucose-fed anaerobic sequencing batch reactor (ASBR) under different F/M ratios was investigated. Glucose added was quickly taken up by fermentation bacterial in anaerobic digestion, then partly degraded directly to volatile fatty acid (VFA, accounted for 34%-38% of COD-fed) and partly accumulated transiently in the cell as glycogen (accounted for 41%-46% of COD-fed) and degraded to VFA in the following. The bacterial accumulation capacities increased with F/M. The maximum specific storage capacities could reach as high as 116.8, 81.1 and 62.4 mg/g as F/M (COD/VSS) was controlled in 0.27, 0.20 and 0.14 respectively. VFA production rate slowed down due to glucose storage, which resulted in low VFA accumulation and guaranteed a stable operation in ASBR under high loading rate.

The denitrification and excessive P removal can be realized by denitrifying phosphate-accumulating organisms (DNPAOs) under low carbon condition. DNPAOs use poly-3-hydroxy- butyrate (PHB) as electron donor, and use nitrate and nitrite as electron acceptor during the denitrifying phosphate uptake. In this study the biological phosphorus removal granular sludge was induced into the denitrifying and phosphate uptake granular sludge under an anaerobic/anoxic/aerobic alternating operation (referred to as an A/A/O) in a sequencing batch reactor (SBR). When the system is stable, the P and N removal ratio is over 90% and 93% respectively; the release phosphorus is 25-33 mg/L at anaerobic stage; 1g NOx-N approximately takes up P 1.3 g at anoxic stage. In the typical cycle the anaerobic maximum specific release phosphorus rate (max. SRPR) is 18.39 mg/(g x h); the anoxic max. specific uptake phosphorus rate (SUPR) and the max. specific denitrification rate (SDNR) is 23.72 mg/(g x h) and 18.19 mg/(g x h) respectively; the aerobic max. SUPR is 17.15 mg/(g x h). The fraction of DNPAOs rises from 14.9% to 80.7%. Compared with the physical-chemical property of the biological phosphorus removal granular sludge, the settling velocity and the specific gravity of the denitrifying phosphate uptake granular sludge is elevated 0.16-0.7 times and 0.0031 respectively.

Sequencing batch reactor, treating simulated municipal wastewater for N removal and operated at near the minimum SRT (solids retention time) for nitrification (in reactor 2), was seeded daily with nitrifying biomass accumulated with reject water (in reactor 1) came from Xi' an Dengjiacun wastewater treatment plant. Comparison of the nitrification ability, the characteristics of the activated sludge before seeding and after seeding was made. The experiment result shows that, the maximum nitrification rate of the activated sludge in the reactor 1 reached 81.4 mg/(L x h). The effluent concentration of NH4+ -N of the reactor 2 decreased at a rate of 0.992 mg/(L x d) (R2 = 0.903), and the maximum nitrification rate increased 1.36 times. Once seeding was terminated, the effluent concentration of NH4+ -N increased at a rate of 1.956 mg/(L x d) (R2 = 0.999), and nitrification caused by seeding was not completely disappeared after seeding was stopped for 34 d. The amount and varieties of protozoa and the value of SVI in the reactor seeded with nitrifiers increased during the initial time of seeding, but were recovered when the reactor 2 reached stable state.