{"id":116557,"date":"2023-03-04T18:15:50","date_gmt":"2023-03-04T23:15:50","guid":{"rendered":"https:\/\/savethewater.org\/?p=116557"},"modified":"2023-03-04T18:15:50","modified_gmt":"2023-03-04T23:15:50","slug":"thermal-hydrolysis-of-sewage-sludge-an-upgrade-in-wastewater-management-technology","status":"publish","type":"post","link":"https:\/\/savethewater.org\/thermal-hydrolysis-of-sewage-sludge-an-upgrade-in-wastewater-management-technology\/","title":{"rendered":"Thermal Hydrolysis of Sewage Sludge: An Upgrade in Wastewater Management Technology"},"content":{"rendered":"

By Sakshi Kabra Malpani, <\/span>Publishing Associate: Researcher and Writer <\/span>at Save the Water\u2122 | March 04, 2023<\/span><\/p>\n

Pure and clean drinking water is our basic right. Poor and outdated wastewater management technologies are one of the big hurdles on this road. <\/span>Thermal hydrolysis of sewage sludge is an upgraded technology to treat wastewater<\/span><\/a>. <\/span>Upmanu Lall, director of the Columbia Water Center<\/span><\/a> has also stated that it\u2019s high time <\/span>to improve wastewater treatment technologies<\/span><\/a> to secure safer drinking water for coming generations.<\/span><\/p>\n

Thermal Hydrolysis<\/span><\/h2>\n

Thermal hydrolysis uses steam to <\/span>treat sewage sludge<\/span><\/a> or wet organic wastes present in wastewater. It\u2019s used prior to <\/span>anaerobic digestion<\/span><\/a> in wastewater treatment plants. This process requires high temperatures\u00a0 of around 140 to 170 \u00b0C and pressure of about six to nine bars.<\/span><\/p>\n

During this process, steam releases energy at a high pressure. This increases the reactivity of water and destroys the chemical bonds of the sewage sludge. Post wastewater treatment, people use sewage sludge as bio-compost to enrich soil nutrients. Thus, it\u2019s very important to treat sewage sludge appropriately.<\/span><\/p>\n

Sewage Sludge<\/span><\/h2>\n

Wastewater treatment plants treat wastewater from sewage systems, and solid wastes are separated from liquid wastes. <\/span>These solid wastes form sewage sludge, which can then be further treated or processed by thermal hydrolysis.<\/span><\/a> Sewage sludge has two types: <\/span>primary sludge and secondary\u2013or waste-activated\u2013sludge<\/span><\/a>. Primary sludge has higher fibrous and lipid content, but less phosphorus and protein content. In contrast, secondary sludge contains more organic matter such as carbohydrates, proteins, microbial cells, etc.<\/span><\/p>\n

After thermal hydrolysis, anaerobic digestion of the sewage sludge takes place, where bacteria breaks it down. Sewage sludge may contain dangerous chemicals and metals leached from industrial, household, municipal, and medical wastes. It also contains non-biodegradable organic matter.<\/span><\/p>\n

Steps of Thermal Hydrolysis<\/span><\/h2>\n

Thermal hydrolysis is carried out in a batch process. The apparatus consists of <\/span>a pulper, reactor, and flash tank<\/span><\/a>. The process follows three steps:<\/span><\/p>\n

    \n
  1. The sewage sludge is constantly fed into the pulper and preheated at about 100 \u2103.<\/span><\/li>\n
  2. From the pulper, the warm sludge goes to the reactor. In each system, there are about two to five reactors placed. Once the reactor gets full, it\u2019s sealed. Steam is flushed inside, and the temperature of the reactor increases up to 180 \u2103 at a pressure of about seven bars. The sludge is treated here for about half an hour to kill bacteria and other pathogens.<\/span><\/li>\n
  3. Afterwards, sterilized sludge is fed into the flash tank at an atmospheric temperature. This abrupt reduction in pressure damages the cells of organic material. When the pressure drops suddenly, steam is produced and is again flushed to the pulper, which is then reused there.<\/span><\/li>\n<\/ol>\n

    The treated warm sewage sludge is then cooled to room temperature using heat exchangers. Lastly, it\u2019s fed to digesters for the next process of anaerobic digestion.<\/span><\/p>\n

    Advantages of Thermal Hydrolysis<\/span><\/h2>\n

    Thermal hydrolysis has multiple benefits:<\/span><\/p>\n