The impact of recycling sludge on water quality in coagulation for treating low-turbidity source water

Chen, Ting; Ya-tong, XU; Wang, Dong; Shi, Wenxin; Cui, Fuyi

doi:10.1080/19443994.2015.1070762

Cited by 8 publications

(3 citation statements)

References 20 publications

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“…Results of the study may not directly decipher the mechanism but are suggestive of probable modes of particle removal. The contracting and expanding blanket of flocs in a PFBC provides a fluidized zone of high solids concentration, which abets nucleation by providing surface sites, increases detention time of flocs, and brings into play few additional mechanisms of coagulation–flocculation like contact stabilization (Hauduc et al, 2019; Hendricks, 2006) and enmeshment (Chen et al, 2016). These processes individually/combined may help in reducing the turbidity of water clarified.…”

Section: Resultsmentioning

confidence: 99%

Performance assessment of pulsating floc blanket clarifiers and conventional clariflocculators in pilot‐scale models

Srivastava

Brighu

Gupta

2020

Water Environment Research

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Continuous upflow pilot plants based on conventional clariflocculation (CC) and pulsating floc blanket clarification (PFBC) technologies were designed and fabricated for a capacity to treat about 8,000 L/day, to understand the fundamental differences in their functioning and assess their relative performance, especially under low turbidity conditions. Influent turbidity varying from 2 to 10 NTU was treated using coagulant alum, and efficiency of CC and PFBC in terms of average turbidity removal was found to be 23% and 48%, respectively. On observing this vast difference, it was postulated that total residual aluminum should also be lower in water treated from PFBC. Experiments and MLR analysis confirmed the hypothesis, with residual aluminum ranging from 0.055 to 0.040 mg/L and 0.036 mg/L to below detectable levels for CC and PFBC, respectively. These findings are of high significance, since minimization of residual aluminum in drinking water is a priority of WHO due to its reported neurotoxicity and can be complied with simple replacement of CC with PFBC. Practitioner points Pulsating floc blanket clarifier (PFBC) performed better than conventional clariflocculator (CC) in terms of turbidity removal. Pulsating floc blanket allowed more effective utilization of coagulant alum, resulting in significantly lower residual aluminum in clarified water. Turbidity levels of influent and effluent are related to residual aluminum in treated water. PFBCs are more compact and modular, and can facilitate a good alternative to CCs.

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Section: Resultsmentioning

confidence: 99%

Performance assessment of pulsating floc blanket clarifiers and conventional clariflocculators in pilot‐scale models

Srivastava

Brighu

Gupta

2020

Water Environment Research

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“…The turbidity remaining in the clarified water by PFBC was 0.42 NTU on an average with standard deviation (σ) of +0.4, whereas for CC, an average residual turbidity of 1.61 NTU (σ ¼ +0.3) was observed. The results indicate that the fluidized zone of high solids concentration provided by the contracting and expanding blanket of flocs in a PFBC improved destabilization of colloidal particles, perhaps by contact flocculation (Hendricks 2006) and charge-neutralization (Chen et al 2016;Lin & Ika 2019b). As the freshly formed microflocs sift upwards through the floc blanket, constituted primarily of well-grown large flocs, collisions between these disparately sized particles occur, resulting in adsorption like flocculation caused by entrapment due to bridging and charge-neutralization mechanisms.…”

Section: Zeta Potential and Turbiditymentioning

confidence: 96%

Characterization of particles and their relation with residual aluminum in water treated with pulsating floc blanket clarifiers and conventional clariflocculators using PACl

2021

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A pulsating floc blanket clarifier (PFBC) employing cyclic contractions and rarefactions to a bed of densely concentrated suspension of flocculated particles in fluidized state, was compared with conventional clariflocculator (CC) at pilot scale (8,000 L/day) in continuous mode of operation. For influent turbidity varied from 2 to 20 NTU, coagulation-flocculation behavior exhibited under the two fundamentally different treatment processes with PACl influenced inter-related performance parameters. The residual turbidity was found lower by 74%, flocs and fine colloids in suspension larger by 73 and 75% respectively, and the total and dissolved residual aluminum lower by 50 and 49% respectively on average for PFBC compared to CC. Particulate form comprised major fraction (≈72%) of total residual aluminum for both. PFBC abetted formation of a more consolidated floc structure which rendered the shape, size and morphology such that the settling velocity was 50% to 410% higher than that of the CC flocs. Reaction-limited aggregation (RLA) process and inter-particle bridging were dominant and the resulting floc structure and its formation mechanism have been presented.

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“…Sludge recycling to the flocculation process is beneficial for solid settling and subsequent dewatering in part due to using residual coagulation and flocculation chemicals in the sludge [7]. It is also known to enhance the efficiency of turbidity reduction in low-turbidity raw water [8].…”

Section: Introductionmentioning

confidence: 99%

Investigation of Mineral-Processing Wastewater Recycling Processes: A Pilot Study

Park

Han

2018

Sustainability

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Mineral processing requires large amounts of water, but, often in the remote locations of many mines, sufficient fresh water frequently cannot be supplied. Therefore, recycling of water is important in mineral processing and enhancing the efficiency of the liquid-solid separation and dewatering steps in mineral processing wastewater treatment is critical. The objectives of the study were to evaluate the effect of anionic flocculant dosage and sludge recycling (SR) on solid removal and sludge dewaterability. Different combinations of the flocculant dosage with and without SR were applied in a mineral-processing wastewater treatment pilot plant. Increasing the amount of flocculant dose of 1.1% v/v (flocculant solution to wastewater) did not significantly decrease the turbidity of the treated water, while the combination of a flocculant with SR increased the zeta potential. Increasing flocculant dose adversely affected dewaterability, although the dewaterability of the 0.6% v/v flocculant-treated sludge significantly increased after aging of the sludge. Sludge recycling was effective for increasing the dewaterability, and a flocculant dose of 1.1% v/v with SR led to formation of large flocs that were stable during aging and sonication.

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The impact of recycling sludge on water quality in coagulation for treating low-turbidity source water

Cited by 8 publications

References 20 publications

Performance assessment of pulsating floc blanket clarifiers and conventional clariflocculators in pilot‐scale models

Performance assessment of pulsating floc blanket clarifiers and conventional clariflocculators in pilot‐scale models

Characterization of particles and their relation with residual aluminum in water treated with pulsating floc blanket clarifiers and conventional clariflocculators using PACl

Investigation of Mineral-Processing Wastewater Recycling Processes: A Pilot Study

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