Field Testing New Technology for Faecal Sludge Treatment
Country: South Africa
Approximately 31% of South African households use pit latrines, totalling about 4 million nationally. Many pit latrines in poor urban areas are full and need immediate emptying, with faecal sludge (FS) transported to centralized facilities for treatment. FS management is a significant challenge for South African municipalities. Since 2010, research has focused on developing innovative, sustainable FS treatment technologies that encourage the use of treatment by-products. Technologies like black soldier fly larvae, thermal drying, and solar drying have been trialled but their full-scale sustainability is still under investigation.
As part of the ongoing effort to find effective FS treatment technologies, the client funded this project to evaluate the enhanced hydrothermal polymerization (EHTP) process for treating FS from pit latrines. A pilot reactor was installed at Zeekoegat WWTP, processing FS from VIP latrines in eThekwini and Kameeldrift, as well as FS mixed with primary sludge (PS) and waste activated sludge (WAS). Analyses showed that the EHTP process effectively sterilized the FS, producing hydrochar and effluent that met ISO 3180 and DWS guidelines. The hydrochar had a higher calorific value and nutrient content than the FS, making it suitable for use as a biofuel, soil conditioner, or building material. Co-processing FS with wastewater sludge improved the hydrochar’s characteristics.
The project demonstrated that the EHTP process can effectively treat FS, creating opportunities for adopting circular economy principles in sanitation and waste management in low-income communities
Dates Started/Ended: 2019/2021
Project Title: Evaluation and Field Testing of an Emerging Hydrothermal Polymerisation Process for Treatment of Faecal Sludge from Low-Cost Sanitation Systemsn
Applying an Emerging Technology to Remove EDCs from Sludge
Country: South Africa
Conventional technologies used in sludge treatment are not consistently efficient in removing all EDCs of concern. Residual EDCs can therefore enter the environment through sludge disposal routes such as land application where the EDCs can potential accumulate and leach into ground water or get taken up by plants. This concern has consequently stimulated research into the efficiency of EDCs from wastewater sludge in recent years.Themajority of the research has however focused on removal of EDCs by conventional treatment processes like anaerobic digestion with very little research on alternative treatment technologies. In South Africa, minimal research has been carried out on EDCs in wastewater and sludge as well as associated technologies that can enhance EDC removal at conventional WWTPs. Considering that the sludge management regulations in South Africa advocate for beneficial utilization including land disposal and reuse for agriculture, understanding the levels of EDCs in treated sludge and measures to lower them is important. To address some of the research gaps the WRC funded this project as part of the ongoing research on EDCs. The main objectives of the project were to:
•Evaluate the efficiency of an emerging sludge treatment technology at pilot scale in removing targeted EDCs from various types of sludge generated at a local WWTP
•Compare the results from the pilot study with conventional anaerobic digestion as well as other technologies
The scope of the project included technical and economic evaluation of implementing each technology at a typical South African WWTP, conducting a knowledge dissemination workshop and preparation of a project report. The emerging enhanced hydrothermal polymerisation Polymeric Carbon Solid (PCS) process was selected for evaluation. A previous study by Musvoto et al. (2018) at laboratory scale showed that the PCS technology is capable of achieving67 – 100% removal of some EDCs (carbamazepine, methylparaben, Bisphenol A and chloramphenicol) from various sludge types. A 60 litre pilot reactor was located at the City of Tshwane‘s Daspoort WWTP. Batches of primary sludge (PS), waste activated sludge (WAS), mixed PS and WAS and anaerobically digested sludge (DS) from the plant were processed in the pilot reactor. Both the sludge feedstock and produced hydrochar were analysed for selected target EDCs based on previous research at Daspoort WWTP as well as compounds of concern identified by the GWRC.
Dates Started/Ended: 2017/2019
Project Title: Application of an Emerging Technology for the Removal of Endocrine Disrupting Compounds in Wastewater Sludges
Applications of Sludge Derived Activated Carbon
Country: South Africa
This project investigated the viability of using waste derived adsorbents to remove heavy metals from wastewater effluent. The performances of an activated carbon produced by pyrolysis of sludge hydrochar (generated from enhanced hydrothermal polymerisation of combined primary and waste activated sludge) was investigated. Laboratory scale tests and pilot scale adsorption column tests were conducted to evaluate the performance of the hydrochar activated carbon (HAC) and C-GAC in removing heavy that are included in the South African National Standard (SANS) 241 for potable water. Adsorption kinetics and isotherms were determined for a mono-element solution containing Pb (II) ions for both C-GAC and HAC. The results showed that the performance of HAC was similar to C-GAC with both having an adsorption capacity and removal of Pb (II) of 1.5 mg/g and 99%respectively. Further laboratory scale adsorption tests and pilot scale column tests assessed the performance of the activated carbons in removing heavy metals from secondary clarifier effluent from a BNR activated sludge plant. The studies indicated that performance of HAC and C- GAC was closely similar for the elements that were above the detection limit (Fe, Ni, Mn and Zn) with removals above for 80% The adsorption experiments showed an order of adsorption of Fe> Ni> Mn > Zn for both C-GAC and HAC at pilot scale.
The study results indicate that HAC has potential to be used as an adsorbent in the tertiary treatment of final effluent from WWTPs for reuse.
Start/End: 2020/2023
Project Title: Advancing Circular Economy in the Water Sector: Utilization of Hydrochar from Sludge Treatment in a Novel Technology for Wastewater Effluent Recovery and Reuse