An anaerobic-anoxic/oxic (A2/O) multi-phased biological process called "phased isolation tank step feed technology (PITSF)" was developed to force the oscillation of organic and nutrient concentrations in process reactors. PITSF can be operated safely with a limited carbon source in terms of low carbon requirements and aeration costs whereas NAR was achieved over 95% in the last aerobic zone through a combination of short HRT and low DO levels. PCR assay was used for XAB quantification to correlate XAB numbers with nutrient removal. PCR assays showed, high NAR was achieved at XAB population 5.2 × 10(8) cells/g MLVSS in response to complete and partial nitrification process. It was exhibited that low DO with short HRT promoted XAB growth. Simultaneous nitrification and denitrification (SND) via nitrate were observed obviously, SND rate was between 69-72%, at a low DO level of 0.5 mg/l in the first aerobic tank during main phases and the removal efficiency of TN, [Formula: see text], COD, TP was 84.7 .97, 88.3 and 96% respectively. The removal efficiencies of TN, [Formula: see text], and TP at low C/N ratio and DO level were 84.2, 98.5 and 96.9% respectively which were approximately equal to the complete nitrification-denitrification with the addition of external carbon sources at a normal DO level of (1.5-2.5 mg/l).

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The performance of a new pilot-scale six tanks activated sludge process has been evaluated for 303 d, receiving real domestic wastewater with a flow rate of 15-24.4 L/h. Partial nitrification via nitrite and microbial community structure were investigated in this system. The result shows that the nitrite accumulation rate was achieved successfully over 94% in the last aerobic compartment through a combination of short hydraulic retention time and low dissolved oxygen (DO) level. Fluorescence in situ hybridization analysis was used to correlate ammonia-oxidizing bacteria (AOB) numbers with nutrient removal via nitrite. It was shown that in response to complete and partial nitrification modes, the numbers of AOB population were 7.7 x 10(7) cells/g mixed liquor suspended solids (MLSS) and 5.31 x 10(8) cells/g MLSS, respectively. The morphology of the sludge indicated that there is a small rod-shaped and spherical cluster which was mainly dominantly bacterial according to scanning electron microscope. Higher pollutant removal efficiencies of 86.2%, 98%, and 96.1%, for total nitrogen, NH4+ - N, and total phosphorus, respectively, were achieved by a long-term operation of the six tanks activated sludge process at a low DO concentration and low chemical oxygen demand to nitrogen ratio which were approximately equal to the complete nitrification-ldenitrification with the addition of an external carbon source at a concentration of 1.5-2.5 mg/L.

This study investigates the suitability of Garmat Ali river (Iraq) for irrigation uses. Two stations were chosen: station A; far from any polluted water discharge point, and station C; near to a very contaminated water discharge point). Water samples were picked up and tested for pH, electrical conductivity, total dissolved solids, sodium, potassium, calcium, magnesium, bicarbonate, sulfate, chlorine, and nitrate. Three samples were collected in January and March 2019 from each site, to reflect the wet season in Iraq. Besides the classification of water quality parameters of Garmat Ali river for watering, other parameters were also calculated, such as sodium adsorption ratio, soluble sodium percentage, exchangeable sodium percentage, magnesium hazard, kelly ratio, permeability index, and potential salinity. According to the Food and Agriculture Organization (FAO) guidelines, the overall results showed that the salinity and chlorine were within the range that causing severe problem to plants. In addition, sodium toxicity and hazard were classified the river water as unsuitable for irrigation. Potential salinity was under the class of unsuitable for irrigation. Bicarbonate hazard was under the category “slight to moderate”. However, the remaining parameters were within the accepted range. Most of the contaminants were higher in the polluted station.

The present work focuses on the investigation of denitrifying phosphorus removal organisms (DPB) in a novel two-sludge denitrifying phosphorus removal process by combining chemical with microbial analysis. When the two-sludge process operated stably over one year, good phosphorus (P) release and P uptake performance of activated sludge samples collected from this process were present in anaerobic and anoxic conditions, respectively, via batch test, showing that the ratio of P release specific rate to P uptake specific rate was 1.31. The analysis of energy dispersive spectrometry (EDS) showed that P content of activated sludge samples collected at the end of anoxic phase was 12.3% of dry weight, further demonstrating the existence of microorganisms responsible for phosphorus removal in this two-sludge process. From polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis, the presence of microorganisms mostly belonging to the phyla Firmicutes and Proteobacteria was observed, previously evidenced in the phosphorus removal wastewater treatment process. Fluorescence in situ hybridization (FISH) quantitative analysis showed thatAccumulibacterresponsible for phosphorus removal was dominant in this two-sludge process, accounting for 69.7% of all bacteria in activated sludge. These results obtained from chemical and microbial analysis in this study suggested that denitrifying phosphorus removal microorganisms were completely enriched in the two-sludge process proposed here.

Two enhanced biological phosphorus removal (EBPR) reactors were started up at low temperatures to obtain microorganisms responsible for aerobic and anoxic phosphorus removal, namely polyphosphate-accumulating organisms (PAO) and denitrifying PAO (DPAO), and their operational performance and microbial community were together investigated in the hope of assessment of the effectiveness of the EBPR process at low temperature by combining chemical analysis and microbial community structure evolution based on polymerase chain reaction-denaturing gradient gel electrophoresis. When two reactors reached the steady state after 40 and 80 days for the anaerobic-aerobic (AO) and anaerobic-anoxic (AA) reactor operation in AO and AA modes, respectively, a good ability of anaerobic phosphorus release and aerobic or anoxic phosphorus uptake was present both in these two reactors. During this start-up process, a total of 22 bands were detected in seed, AA and AO sludge samples, including Alpha-, Beta-, Gamma- and Deltaproteobacteria, as well as Chlorobi, Firmicutes, Bacteroidetes and Actinobacteria. Of all the bands, only four bands were present in all the lanes, suggesting that shift in microbial community occurred greatly depending on the electron acceptors in this study. From evolutionary tree, it was found that microorganisms related to DPAO mostly belong to the phylum Betaproteobacteria, while microbes corresponding to PAO were present in several phyla. Overall, the new strategy proposed here was shown to be feasible for the enrichment of PAO and DPAO at low temperature, and may be regarded as a new guidance for the application of EBPR technology to practice, especially in winter.

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