Quality monitoring of composting processes of wastewater sludge in Alexandria

There are two wastewater primary treatment plants in Alexandria (west and east). The produced primary sludge is mechanically dewatered and transported to sludge disposal site 9N where composting is carried out. However, prior to 1970, composting played a very minor role in sludge or solid wastes treatment because of greatly unfavorable balance between its economics and those of the principal competing option, namely landfill disposal. This study aims at monitoring and evaluating the composting process of demitted sludge produced from Alexandria wastewater treatment plants. Ten batches of sludge were composted. During the composting process the batches were been investigated and followed up to 3 months. Representative samples (10 for each batch) were taken from these batches at the start of windrowing and after each turning (4-15 days) and were analyzed for physical; chemical; bacteriological; and parasitological characteristics, heavy metals, and plant nutrients. Results revealed that C/N ratio of the final compost product comply with the decree of the Minister of Agriculture No. 100 11967, while moisture, C%, and TKN did not. Heavy metals, faecal coliforms, and helminthes complied with the decree No. 222/2002 for the Minister of Housing, Utilities, and Urban Communities. Moisture had positive correlation with both C and VS and negative correlation with pH. Temperature had negative correlation with TKN. Both total and faecal coliforms had negative correlation with temperature and positive correlation with C, N, and VS. It is recommended to optimize the quality of the produced sludge compost by use bulking agent rich in carbon and nitrogen as Hay or Rice straw, instead of the matured sludge compost.