Enhanced flocculation of two bioflocculation-producing bacteria by secretion of Philodina erythrophthalma.

Bdelloid rotifer are reported to play a promoting role in microbial aggregation and floc formation in activated sludge systems; however, the mechanisms involved in this process are unclear. This study explores the effect of a rotifer secretion (RS) from the species Philodina erythrophthalma on the flocculation and growth of two bioflocculation-producing bacteria isolated from activated sludge. Results show that although the secretion has weak bioflocculability in itself, it can significantly enhance the flocculability of bioflocculation-producing bacteria and promote formation of microbial aggregation and floc. The possible mechanism is that the RS causes an increase in the bacteria densities and extracellular polymeric substance contents. The improvement of flocculability using RS shows an S-curve changing tendency with collection time, and corresponds with the first-order model with secretion dosage. Chemical composition analysis shows that low contents of non-protein organic nitrogen and polysaccharides are found in the RS, which implies that RS acts more like a growth-promoting substance or infochemical than as a nutrient in the promotion of bacterial growth. In conclusion, the findings provide a novel and potential strategy for promoting sludge floc formation using the infochemical secreted by this rotifer.

Rapid start-up of a nitrifying reactor using aerobic granular sludge as seed sludge.

In this study, the effectiveness of aerobic granular sludge as seed sludge for rapid start-up of nitrifying processes was investigated using a laboratory-scale continuous stirred-tank reactor (CSTR) fed with completely inorganic wastewater which contained a high concentration of ammonia. Even when a large amount of granular biomass was inoculated in the reactor, and the characteristics of influent wastewater were abruptly changed, excess biomass washout was not observed, and biomass concentration was kept high at the start-up period due to high settling ability of the aerobic granular sludge. As a result, an ammonia removal rate immediately increased and reached more than 1.0 kg N/m(3)/d within 20 days and up to 1.8 kg N/m(3)/d on day 39. Subsequently, high rate nitritation was stably attained during 100 days. However, nitrite accumulation had been observed for 140 days before attaining complete nitrification to nitrate. Fluorescence in situ hybridization analysis revealed the increase in amount of ammonia-oxidizing bacteria which existed in the outer edge of the granular sludge during the start-up period. This microbial ecological change would make it possible to attain high rate ammonia removal.

Foaming control by automatic carbon source adjustment using an ORP profile in sequencing batch reactors for enhanced nitrogen removal in swine wastewater treatment.

Incomplete denitrification and ammonia accumulation were found to cause proliferation of filamentous microorganisms in sequencing batch reactors (SBRs) for swine wastewater treatment. Foaming was observed in response to the accumulation of 115.2 and 12.2 mg/L of nitrate and ammonia, respectively. The mixed liquor suspended solids (MLSS) level in SBRs was decreased to 2,000 mg/L and the suspended solids in the effluent reached 200 mg/L when foaming appeared. However, the use of swine waste as an external carbon source for enhanced biological nitrogen removal was found to effectively control the foaming caused by filamentous microorganisms. Therefore, an optimum strategy for the addition of swine waste was designed using integrated real-time control to provide pulse input control of slurry based on the "nitrate knee" in the oxidation-reduction potential profile. In this case, the MLSS concentration was maintained at an average value of approximately 7,550 mg/L, while the SS in the effluent was less than 30 mg/L.

Biodegradation of chlordane and hexachlorobenzenes in river sediment.

Contamination of river sediments by persistent organic pollutants (POPs) is a worldwide concern, and microbial degradation is regarded as an important process for removal of POPs from river sediments. To date, there is still a lack of systematic study on chlordane biodegradation in river sediments, and the information on hexachlorobenzene (HCB) biodegradation in river sediments is very limited in Japan. We investigated the anaerobic biodegradation potential of trans-chlordane (TC), cis-chlordane (CC), and HCB in sediment samples collected at three sites along the Kamogawa River in Saitama Prefecture, Japan. Lag period and biodegradation rates of TC and CC in the three sediments varied greatly with their properties and contamination by TC and CC. In contrast, biodegradation of HCB in all three sediments started immediately with the start of the experiment without lag period, and major differences in biodegradation rates among the sediments were not observed. At the end of 20-week anaerobic incubation in the dark at 30 degrees C temperature, degradation rates ranged from 0.0% to 33.0% for TC, 0.0% to 12.0% for CC, and 47.6% to 59.4% for HCB. Results showed that the high-to-low order of biodegradation in the river sediments was HCB>TC>CC. Although the sediments were collected in the same river, their biodegradation potential varied with properties. Sediment with rich organic content and contamination by TC and CC or HCB was observed to have high biodegradation rates for these pollutants. In addition, biodegradation of TC, CC and HCB was companied by obvious methane generation and drop of oxidation-reduction potential (ORP).

Anaerobic/oxic/anoxic granular sludge process as an effective nutrient removal process utilizing denitrifying polyphosphate-accumulating organisms.

In a biological nutrient removal (BNR) process, the utilization of denitrifying polyphosphate-accumulating organisms (DNPAOs) has many advantages such as effective use of organic carbon substrates and low sludge production. As a suitable process for the utilization of DNPAOs in BNR, an anaerobic/oxic/anoxic granular sludge (AOAGS) process was proposed in this study. In spite of performing aeration for nitrifying bacteria, the AOAGS process can create anaerobic/anoxic conditions suitable for the cultivation of DNPAOs because anoxic zones exist inside the granular sludge in the oxic phase. Thus, DNPAOs can coexist with nitrifying bacteria in a single reactor. In addition, the usability of DNPAOs in the reactor can be improved by adding the anoxic phase after the oxic phase. These characteristics enable the AOAGS process to attain effective removal of both nitrogen and phosphorus. When acetate-based synthetic wastewater (COD: 600 mg/L, NH4-N: 60 mg/L, PO(4)-P: 10 mg/L) was supplied to a laboratory-scale sequencing batch reactor under the operation of anaerobic/oxic/anoxic cycles, granular sludge with a diameter of 500 microm was successfully formed within 1 month. Although the removal of both nitrogen and phosphorus was almost complete at the end of the oxic phase, a short anoxic period subsequent to the oxic phase was necessary for further removal of nitrogen and phosphorus. As a result, effluent concentrations of NH(4)-N, NO(x)-N and PO(4)-P were always lower than 1 mg/L. It was found that penetration depth of oxygen inside the granular sludge was approximately 100 microm by microsensor measurements. In addition, from the microbiological analysis by fluorescence in situ hybridization, existence depth of polyphosphate-accumulating organisms was further than the maximum oxygen penetration depth. The water quality data, oxygen profiles and microbial community structure demonstrated that DNPAOs inside the granular sludge may be responsible for denitrification in the oxic phase, which enables effective nutrient removal in the AOAGS process.

Aerobic biodegradation behavior of nonylphenol polyethoxylates and their metabolites in the presence of organic matter.

In this paper, the aerobic biodegradation behavior of nonylphenol polyethoxylates (NPnEOs) with ethoxy (EO) units of specific lengths, which were fractionated using high-performance liquid chromatography(HPLC) with photodiode array detection, was studied in the presence of different types of organic materials. NPnEOs and their related metabolites under a modified OECD 301E biodegradation test were monitored using liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS). Biodegradation tests in the presence of organic matters, such as methanol, glucose, and yeast extract, showed the formation of the corresponding nonylphenol polyethoxy carboxylates by the oxidation of the terminal alcoholic group. However, aerobic biodegradation tests without organic matter revealed that NP2EO and NP3EO were predominant metabolites of the long-chain-oligomer precursor system which undergo fast and complete shortening. Degradation rates were higher for the long-chain oligomers than for shorter ones. The degradation pathway of NPnEOs was greatly influenced by the presence or absence of organic matter. Organic materials such as those given above apparently play a significant role in the formation of the carboxylated metabolites of NPnEOs.

Integrated real-time control strategy for nitrogen removal in swine wastewater treatment using sequencing batch reactors.

A new integrated real-time control system was designed and operated with fluctuating influent loads for swine wastewater treatment. The system was operated with automatic addition control of an external carbon source, using real-time control technology, which utilized the oxidation-reduction potential (ORP) and the pH as parameters to control the anoxic phase and oxic phase, respectively. The fluctuations in swine wastewater concentration are extreme; an influent with a low C/N ratio is deficient in organic carbon, and a low carbon source level can limit the overall biological denitrification process. Consequently, a sufficient organic source must be provided for proper denitrification. The feasibility of using swine waste as an external carbon source for enhanced biological nitrogen removal was investigated. The real-time control made it possible to optimize the quantity of swine waste added as the load fluctuated from cycle to cycle. The average removal efficiencies achieved for TOC and nitrogen were over 94% and 96%, respectively, using the integrated real-time control strategy.

Effectiveness of oxidation-reduction potential and pH as monitoring and control parameters for nitrogen removal in swine wastewater treatment by sequencing batch reactors.

Two bench-scale sequencing batch reactors (SBRs) were operated in a fixed hydraulic retention time study to investigate the effectiveness of oxidation-reduction potential (ORP), pH and dissolved oxygen as parameters for indicating denitrification followed by nitrification in SBRs for swine wastewater treatment. The ORP and pH profiles were monitored and evaluated under different denitrification and nitrification conditions with and without a supplemental carbon source. With a low C/N ratio, and using a suitable C/N ratio adjustment control, ORP and pH could be used as monitoring and control parameters in both the anoxic and oxic phases for practical swine wastewater treatment. High-level accumulation of nitrate was observed without any C/N ratio adjustment. In this case, ORP and pH were not useful for monitoring denitrification followed by nitrification in SBRs. According to our research, with regard to N removal, it would be better to use pH as a parameter during the oxic phase and ORP as a parameter during the anoxic phase. Using a suitable adjustment of a ON ratio in the influent by adding swine slurry, a high total nitrogen removal efficiency of up to 95.5% was reached. It was found that, in this case, the use of ORP and pH as parameters for real-time control processes was possible in swine wastewater treatment.