[Study on dewatering of activated sludge under applied electric field].

Abstract

For an electro-dewatering process of activated sludge (AS), the effect of pH and conductivity of AS, flocculation conditioning and operation factors of horizontal electric field (voltage magnitude, method of applying electric field and distance between plates) were investigated, and the corresponding optimum electro-dewatering conditions were also obtained. The results showed that the best electro-dewatering effect was achieved for AS without change of its pH value (6.93) and conductivity (1.46 mS x cm(-1)). CPAM conditioning could lead to the increase of 30%-40% in the dewatering rate and accelerate the dewatering process, whereas a slight increase in the electro-dewatering rate. The electro-dewatering rate for conditioned AS reached 83.12% during an electric field applied period of 60 minutes, while this rate for original AS could be 75.31% even the electric field applied period extended to 120 minutes. The delay of applying the electric field had an inhibition effect on the AS electro-dewatering rate. Moreover, the optimum conditions for AS electro-dewatering were followed: CPAM dose of 9 g x kg(-1), electric field strength of 600 V x m(-1), distance between the two plates of 40 mm, dehydration time of 60 minutes. Under above optimum conditions the AS electro-dewatering rate could approach to 85.33% and the moisture content in AS decreased from 99.30% to 95.15% accordingly.

AI evidence extraction

Main findings

In an electro-dewatering process for activated sludge, best performance was reported without changing sludge pH (6.93) and conductivity (1.46 mS/cm). CPAM conditioning increased dewatering rate by 30%–40% and accelerated the process; conditioned sludge reached 83.12% dewatering in 60 minutes of electric field application versus 75.31% for original sludge even with 120 minutes. Optimum conditions were CPAM 9 g/kg, electric field strength 600 V/m, plate distance 40 mm, and 60 minutes dehydration time, yielding a dewatering rate up to 85.33% and reducing moisture content from 99.30% to 95.15%.

Outcomes measured

• activated sludge dewatering rate
• moisture content reduction
• effects of pH and conductivity on dewatering
• effects of CPAM flocculation conditioning
• effects of electric field operation factors (voltage/field strength, timing of application, plate distance)

{
    "study_type": "engineering",
    "exposure": {
        "band": null,
        "source": "applied electric field (electro-dewatering setup)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "60–120 minutes (electric field applied period); optimum dehydration time 60 minutes"
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "activated sludge dewatering rate",
        "moisture content reduction",
        "effects of pH and conductivity on dewatering",
        "effects of CPAM flocculation conditioning",
        "effects of electric field operation factors (voltage/field strength, timing of application, plate distance)"
    ],
    "main_findings": "In an electro-dewatering process for activated sludge, best performance was reported without changing sludge pH (6.93) and conductivity (1.46 mS/cm). CPAM conditioning increased dewatering rate by 30%–40% and accelerated the process; conditioned sludge reached 83.12% dewatering in 60 minutes of electric field application versus 75.31% for original sludge even with 120 minutes. Optimum conditions were CPAM 9 g/kg, electric field strength 600 V/m, plate distance 40 mm, and 60 minutes dehydration time, yielding a dewatering rate up to 85.33% and reducing moisture content from 99.30% to 95.15%.",
    "effect_direction": "benefit",
    "limitations": [],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "electro-dewatering",
        "activated sludge",
        "electric field strength",
        "CPAM conditioning",
        "pH",
        "conductivity",
        "plate distance",
        "moisture content"
    ],
    "suggested_hubs": []
}

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