Introduction: Municipal Waste Water Treatment Plant is one of the prominent events inthe world in order to preserve the environment. Nevertheless, the activatedsludge processes make this as a highly expansive activity to treat the wastewater with current regulations and requirements. Although, the technologiessuch as Development of bioreactor, Aerobic granular sludge systems are arrived,there is no any significant changes.
But, it is believed that the anaerobictechnology can be a significant solution for this major issue. The anaerobictechnology has been used for the treatment of industrial waste water and sludgetreatment also. The anaerobic condition produces microorganisms and biogas,which can be utilised for the treatment of sludge and energy requirement ofplant respectively. The digested sludge by anaerobic microorganisms can be usedfor the land applications.
Although, this sludge production can improve theeconomy rate, the organic matter in the sewage sludge is very less as largequantity of organic matters are accumulated in the water. Hence, in order toenhance the strength of the sludge, the organic matter has to be extracted fromwater to the sludge as per side stream technology or the Mainline treatment(Direct treatment of low strength water anaerobically) should be followed.Despite, the Side stream sludge treatment is used since many years, some of theadvanced technologies are required to enhance the organic matter in the sludgeand efficiency of the sludge separation process. Also, the mainline treatmentrequires plenty of microorganisms. Municipal waste water’s higher temperature,lower organic strength etc. are not giving a suitable condition for the growthof methanogens.
Hence, the ordinary anaerobic bioreactors such as Up-flowAnaerobic Sludge Blanket (UASB), Expanded Granular Sludge Bed (EGSB) are notproviding higher amount of biomass and washing out them. Therefore, this paperemphasising the following energy producing Anaerobic technologies and theirchallenges for Municipal Waste Water Treatment such as Enhanced side streamanaerobic sludge digestion, Anaerobic Membrane Bioreactor and Microbialelectrochemical system. Enhancedside-stream anaerobic sludge digestion: This is very economical method and almost similar to the regulartreatment plants but based on the more anaerobic technology instead of aerobic systemfor the degradation of organic matter.
There are two main tasks in thisprocess. Firstly, to enhance the concentration of organic matter in the sludgewith very less consumption of energy. Secondly, large amount of anaerobicdigestion of the carbon imposed sludge in order to produce biogas with highenergy. Basically, it is believed that when the anaerobic digestion od sludgeis biomass is consisting massive carbon content, the bio concentration oforganic matter can be achieved automatically. These processes have been donesuccessfully by many treatment plants such as Strass WWTP in Austria. However, inthis process, the energy consumption is quite higher due to lethargicsolubilisation of the organic matter. Hence, few pre-treatments are requiredfor this process such as hydrothermal, microwave irradiation, chemical andbiological treatments etc. in order to make the microorganisms feasible toutilize the sludge.
But, all the methods are consuming higher energy.Nevertheless, the thermal hydrolysis method can utilize very less energy whichis produced by the plant’s heat pumps. The minimal in situ energy by thisprocess along with the separated sludge will require very less or even zero heatenergy for the whole process compared to massive sludge amount in theconventional methods. However, the predetermined process will be depending onthe sludge properties, bio concentration level etc. This progress is achievedexactly by the Blue plains WWTP in the United States. In this plant, theyfollow the same Strass WWTP’s anaerobic side stream technology but along withthe Cambi Thermal Hydrolysis process for lifting the solubility of the biomass.This idea enhances the production of methane twice while compared to theordinary sludge digestion processes. Another problem faced by the plants are less organic contents and unevensludge, which reduces the production of methane.
Provision of organic rich foodwaste along with the obtained sludge can provide a solution for this issue.This method raises the carbon content availability along with the higher yieldof biogas. Furthermore, this method can reduce the bioreactor investment andthe maintenance cost. This idea has been provided in Strass plant over 8 years.Challenges: Thoughthe side stream anaerobic biotechnology is implemented in treatment plants, ithas few technological and economical defects in it. Firstly, the bioconcentration process consumes small amount of oxygen anyway, and few organicmatters are wasted.
Secondly, the sludge less holding process may decrease thestability of the sludge. Hence, in order to avoid the washing out of sludge,the sludge thickening by coagulation process is required. Otherwise, membraneshould be installed for avoiding the washout.
Finally, the anaerobic digesterand pre-treatment devices lead to higher cost and highly corrosive.