Maximising the value of trade waste.
| dc.contributor.advisor | Bajón Fernández, Yadira | |
| dc.contributor.advisor | Pidou, Marc | |
| dc.contributor.author | Berzal De Frutos, Olivia | |
| dc.date.accessioned | 2024-03-13T15:24:39Z | |
| dc.date.available | 2024-03-13T15:24:39Z | |
| dc.date.issued | 2020-12 | |
| dc.description.abstract | Anaerobic digestion (AD) of sewage sludge is a typical treatment method used before its disposal or land application as it has been shown to reduce pathogens, stabilise the sewage sludge and reduce sludge volumes, generating at the same time biogas for energy generation. Anaerobic co-digestion (Aco-D) is used to balance the characteristics of two or more waste in AD to improve performance and increase biogas yield. Aco-D of sewage sludge and trade wastes (TWs) has been seen to have a beneficial effect by balancing nutrients and toxicity. Currently, TWs typically with a lower chemical oxygen demand (COD) concentration of below 50g/L are accepted on large wastewater treatment for treatment with the municipal wastewater in the biological nutrients removal process (BNR). This may have the benefit of balancing the organics/nutrients ratio in the systems but the increased load in both organics and nutrients generally leads to an increase in the cost of treatment which is expected to be compensated by the charge (gate fee) applied to take these TWs. Alternatively, TWs, especially with greater COD content (> 50 g/L) could be considered for Aco-D with sewage sludge on those same sites but this approach requires careful control of TWs loads as they are known to contain toxic compounds that could affect the AD process. Furthermore, the lower strength TWs could also be considered for Aco-D, if concentrated to reach suitable organics content for addition to the AD reactor. However, there is very limited literature on the Aco-D of sewage sludge and TWs, especially when considering the wide range of wastes accepted on sites. Therefore, the potential to use Aco-D on high and low strength TWs was considered in this study. The aim of this project was to understand the effect of TWs in Aco-D with sewage sludge to maximise the benefits and reduce the negative impact of TWs. To achieve this goal, batch and semi-continuous AD experiments with sewage sludge were carried out to investigate the impact of addition of key components of TWs, identified through the study of a data containing the characteristics of 160 TWs and ultimately identify concentrations range in which the compounds may be beneficial or inhibitory. In the batch experiments, methane yield and lag phase inhibitions were observed from 1764 mg TAN/L, 592 mg Zn/L, 22 mg Cu/L, 464 mg Al/L, 4535 mg Cl/L, 162 mg SO₄/L, 92 mg NO₃/L, 25 mg Hg/L and 17 mg As/L using Ammonia sulphate, Zinc chloride, Copper chloride, Aluminium sulphate, Sodium chloride, Sodium sulphate, Sodium nitrate, Mercury sulphate and Sodium arsenate, all highlighting the importance of managing loads on the AD plant. Zinc sulphate and sodium nitrate were further studied in semi-continuous experiments to understand the possible long- term impacts of the compounds in the reactor over long-term operation. Inhibitory values were identified for Zn from 700 mg Zn/L and from nitrate from 2000 mg NO3/L decreasing biogas production to 0 and 20-38 mL/% VS red/d compared with the value for control reactors with only sewage sludge of 80-100 mL/% VS red/d. Accumulation in the solid fraction was observed in the zinc experiments, while nitrate showed an inhibition of the methanogenesis because of the generation of by-products from the denitrification process. The concept of pre- concentrating low organic content TWs in a dead-end filtration cell using microfiltration (MF) and ultrafiltration (UF) membranes was studied, with the concentrates produced and then tested in a batch AD test as 10% of the feed with sewage sludge. The results showed that most of the TWs studied, including wastes from the food, chemical, leather, personal care products and paper industries showed non-effect or beneficial in the Aco-D with sewage sludge except for a resin TWs. Finally, it was demonstrated that an economic benefit can be expected from the co-digestion of the concentrates with sewage sludge from most of those TWs based on the avoided cost of treating the TWs in the BNR and the increase in methane production. Overall, this work demonstrated that it is possible to maximise the value of trade wastes through co- digestion with sewage sludge, but careful addition will be required to ensure optimum operation of the AD. | en_UK |
| dc.description.coursename | PhD in Water, including Design | en_UK |
| dc.identifier.uri | https://dspace.lib.cranfield.ac.uk/handle/1826/20980 | |
| dc.language.iso | en | en_UK |
| dc.publisher | Cranfield University | en_UK |
| dc.publisher.department | SWEE | en_UK |
| dc.rights | © Cranfield University, 2020. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder. | en_UK |
| dc.subject | Anaerobic co-digestion | en_UK |
| dc.subject | sewage sludge | en_UK |
| dc.subject | anaerobic digestion | en_UK |
| dc.subject | biogas | en_UK |
| dc.subject | methane | en_UK |
| dc.subject | inhibition | en_UK |
| dc.title | Maximising the value of trade waste. | en_UK |
| dc.type | Thesis or dissertation | en_UK |
| dc.type.qualificationlevel | Doctoral | en_UK |
| dc.type.qualificationname | PhD | en_UK |