5.4 million m3 of biogas a year for the waste treatment plant in Malta - English Subtitles

hello, my name is octavio navarrete. i am the operations manager at the encina wastewater authority. the encina wastewater authority is a public agency in northwestern san diego county. six public agencies own encina wastewater authority which include the city of carlsbad, the city of vista, the city of encinitas, the buena sanitation district, the leucadia wastewater district and the vallecitos water district. we currently treat approximately 22 million gallons per day,

but we have the capacity to treat up to 40.5 million gallons per day. the first stage in the treatment process is preliminary treatment. wastewater enters our screens building and passes through bar screens and grid separators that remove rags, rocks, and other debris that can damage our equipment. next, wastewater flows to primary sedimentation tanks, where the velocity of wastewater slows down. settable solids and floatable materials separate through the use of skimmers and flights,

these materials are removed and sent to our anaerobic digesters for further treatment. wastewater flows through aeration tanks, where we add oxygen and activated sludge, which are solids removed from later in the treatment process. the activated sludge contains microorganisms which break down any other organic matter in the wastewater. wastewater then flows to secondary clarifiers, where microorganisms and degraded organic material

from the secondary treatment process settle. these solids are then collected and the majority are sent back to the aeration tanks as activated sludge. next, treated wastewater from the secondary treatment process is sent to our pumping station, where it is discharged one and a half miles offshore out into the pacific ocean. at this point, 96 percent of the pollutants have been removed. approximately one third of our treated wastewater is recycled. it is used within the plant for process supply water,

equipment cleaning and sent to our member agencies, which treat it even further to provide recycled water to parks, landscapes and golf courses. the organic material removed by the wastewater treatment process is sent to heated tanks called digesters, where the solids are allowed to decompose in the absence of oxygen for 15-30 days. this process produces biogas, which we use to run four 750 kilowatt electric generators

that supply 70 percent of our facility needs. we take the methane gas out of the digester and burn it in internal combustion engines. their secondary use is for capturing the heat off the engines. we use that to heat up our heat loop water which then in turn keeps the digester at a constant temperature of 97 degrees. the engines are capable of burning both digester gas and natural gas, or a combination of the two.

from this process, we produce approximately 750 thousand cubic feet of biogas each day. the waste heat which is generated by the internal combustion engines is used to heat our anaerobic digesters. the solids from the plant, both primary and secondary, are collected in the digester and they are treated. all the volatile solids are reduced 50-55 percent. one of the bioproducts from that is methane gas, which is used in our cogeneration facility.

over here, we have our fog-receiving facility. it filters fats, oils and grease. fog comes from different restaurants and helps increase our methane production, to help fuel our cogen and drier facilities. we then remove liquid from the digested sludge through the use of centrifuges that operate like the spin cycle on your washing machine. finally, the solids are heated to approximately 200 degrees

in our heat drier to kill off any infectious microorganisms. this process produces a dry, granular product called biosolids that can be used as organic fertilizer. we have two biological towers and one chemical scrubbing tower to control odors. our odor reduction facility number one is a biotower that removes foul air from the influent junction structure, the screenings building and our primary sedimentation tanks. our odor reduction facility number two is a biotower

that removes foul air from our thickening and dewatering process. orf three is a chemical scrubber that removes foul air from our aeration basins. odors are very important to us here at encina, being so close to our surrounding community. one of the things that we've done is we have a self-directed work team. the objective of the self-directed work team is to reduce odors on-site and for our surrounding community.

the self-directed work team does this through a process of continuous improvement, modifying standard operating procedures to minimize or eliminate odors and to do routine inspections of all our facilities.

Tweet

Subscribe to receive free email updates: