Nature Environment and Pollution Technology

Wei Na ¹

Affiliations
1 School of Civil Engineering and Architecture, Wuhan Polytechnic University, Wuhan 430023, CN

Abstract

A solidification/stabilization (S/S) process by using municipal solid waste incineration (MSWI) fly ash was applied to sewage sludge in order to find a safer way for the two wastes (sewage sludge and MSWI fly ash) disposal. The behaviour of pastes fabricated with various mass ratios of Portland cement/MSWI fly ash has been analysed in terms of mechanical strength, microstructure and leaching characteristics. The results showed that the unconfined compression strength (UCS) of solidified sludge decreased with the mixing amount of MSWI fly ash. However, with the addition of 5% MSWI fly ash represented 28 days UCS of 0.31 MPa, satisfying the landfill threshold of 0.3MPa. Scanning electron microscopy investigations revealed that a large amount of ettringite was present in solidified sludge, leading to a crystallizing network in the solidified products, and therefore, the enhancement of the strength. Environmental assessment of the final products in compliance leaching tests demonstrated that the concentration of heavy metals was below the detection limits.

Keywords

Sewage Sludge, Municipal Solid Waste, Incineration Fly Ash, Solidification/Stabilization.

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Wei Na ¹

Affiliations
1 School of Civil Engineering and Architecture, Wuhan Polytechnic University, Wuhan, 430023, CN

Abstract

The few reuses and large stockpile of sewage sludge led to a series of social and environmental problems. This study investigated the possibility of using the sewage sludge and municipal solid waste incineration (MSWI) fly ash as materials to prepare ceramsite by a high temperature sintering process. Two experiments were designed to investigate the addition of sewage sludge and MSWI and sintering treatment. The result showed that the mass ratio of sewage sludge to MSWI fly ash was 8:2 and the the pellets, sintered at 1080°C for 8 min, were beneficial to produce sludge ceramsite. Property tests of sludge ceramsite showed that sludge ceramsite was light (with an apparent density of 680kg/m³), waterproof (with a water absorption of 6.7%), hard (with a compressive strength of 5.4Mpa) and nontoxic (contents of toxic metal leaching test were found to be within the limits of China's regulatory requirement). These results reveal the feasibility of recycling sewage sludge and MSWI fly ash by sintering as a construction material.

Keywords

Sewage Sludge, Municipal Solid Waste, Incineration Fly Ash, Sintering, Sludge Ceramsite.

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Wei Na ¹

Affiliations
1 School of Civil Engineering and Architecture, Wuhan Polytechnic University, Wuhan, 430023, CN

Abstract

Biogas recovery by anaerobic digestion was seen as an ideal way to treat biomass waste-sewage sludge, but has some limitations, such as the low efficient biogas production. In this paper, the combined (alkaline and ultrasonic) pretreatment was proposed for effective sludge anaerobic digestion and the effect of these pretreatments was investigated. It can be seen that this treatment effectively led to the increase of soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFA) concentration. The high concentration of VFA led to an increase in biogas production. Under the optimum combined pretreatment condition (under 6000 kJ/kg TS and with 0.15 mol/L NaOH), the biogas production was nearly 8 times higher than the raw sample. Besides, the SV of sludge was reduced and the settling characteristics of sludge were improved. The results indicated that the combined pretreatment could be an effective method for improving biogas yield.

Keywords

Sewage Sludge, Anaerobic Digestion, Biogas Production, Combined Pretreatment.

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Wei Na ¹

Affiliations
1 School of Civil Engineering and Architecture, Wuhan Polytechnic University, Wuhan, 430023, CN

Abstract

The increase in the number of wastewater treatment plants and the sewage sludge makes it necessary to improve the efficiency of anaerobic digestion of sludge. Pretreatment of sewage sludge has shown important advantages in the sludge anaerobic digestion. This study investigated the effect of using ultrasonication-ozonation pretreatment on the anaerobic digestion process. It can be seen that this treatment effectively led to the increase of soluble chemical oxygen demand (SCOD). The optimal specific energy input was 6000 kJ/kg TS and the ozonation dosage was 0.10 g O₃/g TS. Under the optimum combined pretreatment condition, the biogas production was nearly 4-8 times than the raw sludge sample. It could be concluded that the combined pretreatment of sludge improved the anaerobic digestion of the sewage sludge.

Keywords

Sewage Sludge, Anaerobic Digestion, Biogas Production, Combined-Pretreatment.

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Wei Na ¹

Affiliations
1 School of Civil Engineering and Architecture, Wuhan Polytechnic University, Wuhan, 430023, CN

Abstract

In order to solve disposal problems of solid wastes, sewage sludge from wastewater treatment plants was mixed with dredged sediment to be recycled into lightweight aggregate through sintering process. The effect of sintering temperature, sintering time and mass ratio of sewage sludge to dredged sediment on characteristics of the aggregate were investigated to optimize the lightweight aggregate production process. Experimental results show that the optimal sintering temperature and time were 1150°C and 10 min respectively, and the optimal mass ratio of sewage sludge to dredged sediment was 7:3. It is concluded that sintering temperature and time, and sewage sludge/dredged sediment have a significant effect on the characteristics of lightweight aggregate.

Keywords

Sewage Sludge, Dreged Sediment, Lightweight Aggregate.

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