Public Works Department
Dirty Water.. Where does it go?
by Marie A. Velong
Sirocco and Hyaline Dunston were watching the lot across the street from their house on Jamestown Road in Ocean City, Maryland. Some people had bought the lot and were building a house on it. There was much activity in the street. The children asked their mother what was happening. She said the workers were getting ready to connect the sewer and water to the property from the main pipes in the street. Well, this of course led to a series of questions. Sirocco, whose nickname was Rocco, a breezy, carefree, 9 year-old boy and Hyaline, a.k.a. Ali, his quietly reflective, 7 year-old sister, wanted to know all about where the sewer and water came from, and how it all worked. Their mother said that, maybe, one of the men outside might be able to help; so, outside they went.
They went up to a man who seemed to be in charge. He was standing outside his truck which had the Town of Ocean City emblem on it.
"Sir?" Rocco said politely, "We were wondering if you could explain to us what you are doing?"
The man looked at them gravely, and then smiled and said, "Well... my name is John Brittingham, people call me John Britt or just Britt, and I am the Construction Foreman for the Ocean City Wastewater Department. What are your names?"
Rocco introduced himself and his sister, and then said breathlessly, "Mom said you were putting in the water and sewer...and we wanted to know where the pipes come from and how it works!"
Britt said, "Our crew is putting in the sewer, Rocco, I can tell you a little about that. The Water Department takes care of hooking up the water. It would be better for them to explain their job to you."
Ali asked, "What does the sewer do?"
Britt said, "The sewer is where your dirty water goes. When you wash dishes, take a bath or flush your toilet, that dirty water goes down the drain to the sewer."
"Where is the sewer?" another question from little Ali.
"The sewer main is a pipe that is usually in the road in front of the house; then, there is a smaller pipe which branches off from the main to the property line, we call that pipe the lateral. From the property line, the plumber connects a pipe, the building sewer, to the building drain of your house. The plumber will then 'rough-in' the piping."
"We have a plumbing inspector, Nelson Kelly, who comes to check and make sure the piping is in the right way. That is a rough-in inspection. When the house is finished, the plumber will call for a final inspection. Mr. Kelly will come again and test the pipes with a smoke machine to make sure there are no leaks."
"Why does he do that?" asked Ali.
"When the dirty water goes down the drain, it can make a gas", said the foreman. "What do you think that gas is called?" Britt asked.
"Sewer Gas??" Rocco said hesitantly.
"Good boy!" Britt congratulated.
"Is sewer gas bad?" queried Ali.
"Yes, it is," Britt said nodding, "It can make you sick. Sewer gas doesn't always have an odor, so you don't know if it is there. The smoke from the smoke machine acts like the gas would if there was a leak, but you can see smoke so you can see where the pipe may be leaking," Britt explained, "If the plumbing passes the final inspection, the people can move in."
"But...what happens to all the stuff that goes down the drain?" Rocco wanted to know.
"Ah, there's a good question", said Britt. "What me and my crew take care of is called the Collection System. That is all the pipes and pumping or lift stations that take the dirty water to the Wastewater Treatment Plant."
"What makes the dirty water go to the treatment plant?" asked perceptive Ali.
"Gravity," said Britt, "We have a gravity system. The pipes are installed so that gravity pushes the water. The pumping or lift stations take the water back up to a level where it can run down again. It all goes to the treatment plant."
"What happens when it gets to the treatment plant? Do you take care of it there? What do you DO with all that dirty water?" Rocco asked enthusiastically.
"Whoa, there, young man," Britt chuckled. "Those aren't simple questions! No, I don't take care of the dirty water at the treatment plant. The treatment plant has 38 licensed operators who have been trained to take care of processing and treating the wastewater - that is what we call the dirty water. It goes through several processes that treat both the liquid and solid waste."
"Bob Hastings is the superintendent of the Wastewater Department. Charles Felin is the assistant superintendent. They could give you more information about the treatment process. Maybe your mom could arrange to take you to the Wastewater Department. She could call and see when you could take a tour of the plant," Britt informed them.
"Where is it?" Ali wanted to know.
"It is in the Public Works Complex on 64th Street and Seabay Drive, on the bay-side in Ocean City," Britt said.
Suddenly they heard a voice, "Wastewater Base to Wastewater 5, John?"
"Well, kids, I've enjoyed talking to you, but I've got to go now. See you again sometime." John turned and pulled out his radio, "Go ahead, Jeannette. This is Five."
Ali and Rocco hurriedly waved good-bye to John Britt and ran in to tell their mother. "Mom, Mom, we want you to take us to the Wastewater Department!"
"Now, wait a minute. What ARE you so excited about?" Sandy Dunston, the children's' mother, asked.
"Oh Mom, we had the best time talking to John Britt," said Ali.
"Was that the man I saw you talking to?" their mother wanted to know. "Yes," responded Rocco, "he works for the Town of Ocean City Wastewater Department."
The children proceeded to tell her all they had learned about the dirty water, smoke machine, gravity and the collection system. "Mom," said Rocco, "Britt said we could tour the Wastewater Department to learn what happens to all the dirty water." "Please, Mom, pleeez, can we go?" begged Ali.
Their mom asked, "Did Mr. Britt say how to go about getting this tour?"
"He said to call and see when we could do it," explained Rocco. "Will you call?" he asked.
"Well...it seems you two are interested enough. Sure, I'll call," their mother answered.
Mrs. Dunston phoned the Wastewater Department, and made arrangements for them to go to the treatment plant the following Wednesday. Since it was summer vacation, they busied themselves with all the fun things kids do in the summer in Ocean City.
The big day finally arrived. It was a beautiful, sunny day in late July. There was a pleasant breeze from the ocean and the heat and humidity of the previous week had finally broken. Rocco and Ali couldn't wait to go on their tour.
"I wonder if we'll see John Britt," said Ali. "Don't know," answered her mother, "We'll just have to wait and see."
Their mother drove down Coastal Highway to 64th Street on the bay side. The Wastewater Department was one street after the new Public Safety Building and two streets before the Route 90 bridge. They drove up to the fenced-in area and through the open gates that had a sign that said "Authorized Personnel Only". They made a left, and parked in the area designated for guests. The children noticed the many white brick buildings - all different sizes.
"My, how clean the area looks!" said Mrs. Dunston.
"It does smell a little funny, though, doesn't it, Mom?" said Rocco.
"Yes...but, Rocco, think of all of Ocean City's dirty water coming here," contemplated Mrs. Dunston, "Considering the job this plant has to do, I think its amazing how little odor there is," Mrs. Dunston observed.
They proceeded up the walk past the trees and pink and white petunias, and went in the double doors of the Administration Building. They came to the counter.
"Hello, can I help you?" asked the blond-haired lady sitting at her desk behind the counter. The sign on the counter said her name was Jeannette Murray. Mrs. Dunston introduced herself, "Hi, my name is Sandy Dunston and these are my children Rocco and Ali. We..."
"Oh yes, you came to tour the Treatment Plant," interrupted Jeannette pleasantly, "John has told me all about Rocco and Ali." The children smiled at each other proudly. "Let me call Charles, the assistant superintendent, and find out who will be showing you around." Jeannette reached for the phone and paged Charles' office. While she was talking, a man came out of the office to her right, and smiled at the children and their mother.
"Hello there! My name is Bob Hastings. I am the Department Superintendent. Are you all set to take our nickel tour?" asked Bob.
"Oh, yes," said Rocco, "We can't wait." Ali stood there shyly nodding in agreement.
"Well, you know, the easiest way to explain the treatment plant is that it just enhances Mother Nature's own process of disposal," said Bob, "But, touring the plant will help you understand how that process works. While you're waiting, did Britt tell you how many miles of pipe there are in Ocean City?" Bob asked.
Rocco said, "No, I don't think he did."
"We have over a hundred miles of 6 to 48 inch gravity mains," Bob told them, "about 10 miles of force main and one mile of Ocean Outfall force main."
"Britt told us about gravity pipes, but what is a force main?" Ali asked timidly.
"A force main," replied Bob, "is a pipe in which the wastewater is pushed or forced by pressure put on it at the pump or lift stations."
"But Britt said the pump stations just lifted the water up so gravity could make it go to the treatment plant," argued Rocco.
"That's true," said Bob, "but, there are several pump stations that take the wastewater to a force main instead of the gravity main. Jamestown Road, where you live, is one pump station that works like Britt said. The pump station at 130th Street pumps the wastewater to a force main instead. That force main comes directly to the plant instead of joining the gravity main," Bob further explained, "Come over here, and I'll show you on the map how it works." Bob took the children, followed by their mother, to the maps and showed them the pump stations and gravity and force mains.
Just as he was finishing his explanation, a door next to the map cabinet opened.
"Well, here's Charles Felin. Charles, I want you to meet Rocco, Ali and, their mother, Mrs. Dunston," Bob quickly introduced everyone.
"I'm a little busy right now, Bob, but I think Randy would be able to help with the tour," said Charles. "I'll take everyone over to the Headworks, and maybe Jeannette can get Randy to meet us there," Charles offered.
Rocco, Ali and Sandy Dunston followed Charles out the doors and down the sidewalk. They turned slightly to the right, and headed toward a structure with only a back wall, short side walls and a roof, looking a little like a carport. It was open in the front with shute-like machinery and belts, and was enclosed by a fence with a locked gate.
Charles said, "This building, and the area around it, is called the Headworks. We have it on-line or operating from May 1st to November 1st, when we have our heaviest flow."
"What does 'flow' mean?" asked Ali.
"We use that term to describe all the wastewater that comes or flows to the plant from the Collection System," answered Charles.
"What happens to the flow when it comes to the Headworks?" was Ali's next question.
"When the flow reaches the Headworks, it will go through one of two barscreens. See, if you look down there, you can see them operating," Charles pointed toward an area below them. "The barscreens are there to catch or stop material larger than 3/8 of an inch from coming into the treatment plant. You can see how they automatically clean themselves," he explained. "Now on the other side, we have the grit chambers. They slow down the flow enough to let the sand and grit settle or move downward out of the wastewater. By keeping the larger material and sand out of the treatment plant, we avoid a lot of trouble with our machinery."
"What happens to the stuff from the barscreens and grit chambers?" asked Rocco.
"The material from the barscreens is put into a dumpster, where we treat it with lime - a chemical, not the fruit," Charles said quickly, anticipating the question. "The lime," he explained, "helps to control the odor and break down the material a little. We do the same with the sand, putting it in a dumpster and treating it with lime, but then we take it to drying beds. Eventually, we take both the material from the barscreens and the dried sand to the landfill."
A man came up to them. "Oh," said Charles, "this is Randy Bradford. He'll be taking you on the rest of the tour." Charles introduced everyone, excused himself, and left.
"So, Charles explained about the Headworks, did he?" asked Randy, with a twinkle in his eye. "What does the Headworks do, Rocco?" he asked.
Rocco quickly replied, "It takes stuff out of the wastewater flow so it doesn't mess up the machines. Then, you put lime on it and it goes to the landfill."
"Very good," Randy said, "Let's move on, and see how much you can remember."
Mrs. Dunston looked at her watch, and said, "Randy, do you have any idea how long this tour will take?"
"It kind of depends," he said, "probably the best way to do this would be to just walk around, and I'll point out some of the buildings. Then, we can go back in, and I can explain the process from the diagram we have. It should take, oh...maybe an hour." Mrs. Dunston nodded and said, "That's perfect, let's go."
Randy led the children and their mother around the plant. They popped their heads in at the laboratory, and met Betsy, Cheryl and Alem, who told them a little about the work they did. Betsy, the laboratory supervisor, explained, "We perform tests on the wastewater to make sure it is safe to discharge into the ocean." Since the lab people were very busy, Randy suggested the group should move on.
As they walked around the grounds of the plant, they stopped and talked to several of the operators. The children noticed that some of the buildings had stairs going up the sides of them and railings around the top. One building had a big, orange windsock on top of it. While they were walking, Randy would point at buildings and mention their names.
The group came around to the office, where they had started. Randy led them inside and up the stairs, to a room he called the Conference or Training Room. The room had several long tables with chairs. It had a long blackboard - actually, it was green, with a sign over the top. The sign said "There is no job so important, nor emergency so great, that we cannot take time to do our work safely." On one of the tables, there was a diagram of the treatment plant.
"Pull up a chair," said Randy, "and we'll go over the treatment plant process and answer the question 'Where does the dirty water go?'." They all got seated around Randy and the large diagram.
"Okay now, here is the Headworks," Randy showed them on the diagram, "we went over what happens there. That is what we call 'Preliminary Treatment.' Here we are now," he said pointing to another building on the diagram, "this building is called the Primary Influent Building. It is where the Primary Treatment starts. Underneath part of the office downstairs is the wet well." Randy went on to explain, "The influent - that's dirty water that has not been treated - the influent goes first to a vault and, then, to the wet well in the Primary Influent Building, where it goes through a second set of bar screens and grit chambers. Remember, that's what the Headworks had?" They all nodded, so he went on, "Between November and April, we don't use the Headworks, so the influent would come here first. The wet well bar screens can handle 4 - 6 million gallons a day of influent - dirty water, while the Headworks bar screens can handle the heavier flows - up to 14 million gallons a day."
"Wow," exclaimed Rocco, "that's a lot of dirty water!"
"It sure is," agreed Randy, "anyway, the bar screens, downstairs, are cleaned manually by one of our operators every 2 hours - not anyone's favorite job and you can understand why. During thunderstorms or on weekends, they are sometimes cleaned every hour."
"Why is that?" questioned Mrs. Dunston.
Randy responded, "Because Ocean City is at sea level, storm water can get into the system through manholes, which creates more wastewater and pressure. This dislodges materials that have built up, creating more waste products that collect on the screens. On weekends the increased water usage will do the same thing."
"Oh, I see," Mrs. Dunston nodded.
Randy continued, "The next step in the process is the comminutors. A comminutor has a fine screen with an oscillating or vibrating blade to mash rags and other debris through the screen." Randy pointed to the diagram, tracing where the wastewater traveled. "After the comminutors, the flow will then go through the Primary Influent Pumps to the Equalization Building. This building has 4 holding tanks. Each tank has a 500,000 gallon capacity. Up to 2 million gallons can be held during the peak flow period, which is somewhere between 9 A.M. - 6 P.M.," he explained further, "This is so that a constant flow rate of 8,600 gallons per minute can be maintained. It prevents the surges we used to have to deal with, and allows the plant to work the way it is supposed to work."
"Have I lost you yet?" he asked. The children shook their head no, and their mother said, "That really makes a lot of sense, holding the extra wastewater, what happens next?"
"The flow goes to the splitter chamber," Randy replied, "where it can be directed to any or all of five possible tanks - 3 Clarifiers and 2 Clarigesters." "What are clar-i-fi-ers and clar-i-ges-ters?" asked Ali.
"A clarifier and a clarigester are both settling tanks," answered Randy, "The main difference between them is the how much they can hold. The clarigester is capable of holding more sludge. Sludge is the solid material in the wastewater that settles to the bottom of the tank. When the plant had only one incinerator, the clarigester was useful in holding the sludge until it could be burned."
"What's a 'settling tank'? What does 'settling' mean?" Ali wondered. "Hmm," Randy searched for an explanation she could understand, "Well, let's say you have a jar, and you put water and sand in it, and shake it up. The sand and water are mixed up, but, if you let it sit on the table for a while, the sand sinks to the bottom of the jar, right?"
Ali, listening intently, nodded.
"THAT is called settling," Randy said triumphantly.
"Now, I understand," Ali said, with her mother and Rocco all nodding in agreement.
"Anyway, after the splitter chamber," said Randy, again pointing at the diagram, "it goes to the clarifiers and clarigesters. The flow is slowed to less than 1 foot per second, so the sludge can settle out of the wastewater.
Randy said, "Remember the tanks that looked like above-ground swimming pools?" Everyone nodded.
Randy went on, "An arm moves over the surface of the tank water to skim off grease. Grease or scum is collected, and, later, burned with the sludge. Settleable solids, kind of like the sand in our jar," Randy looked at Ali, who nodded, and then he continued, "will sink to the bottom of the tank. Every 15 minutes a pump comes on, and, for 2 minutes, pumps the solids out of the tank. They are sent to the Primary Thickener, which is another place the sludge or settleable solids are left to settle and thicken."
"That's why they call it a thickener, I bet," Rocco commented.
"Yes sir, you are right on-the-ball," said Randy with a big grin.
"Now, next we have the F/S Incineration Process, and before you ask," he said looking at Rocco, "F/S stands for Fluo-Solids or fluidized solids." "Okay?" asked Randy.
Rocco shook his head, then nodded and, laughing, blurted, "YES!"
So Randy continued, "The Mercobowl is a centrifuge, right here," pointing to the diagram, "It further dewaters and thickens the sludge from the Primary Thickeners. (It works like a washing machine on its spin cycle, when it spins the water out of the clothes.) Then, the thickened sludge mixes with 1400° sand - now, that is real hot!" he declared and went on, "The sludge and the sand get constantly stirred by air, supplied by a blower, turning the sludge into carbon dioxide, steam and a little ash. This is known as wasting. The blower blows sand and ash out of a stack, where it gets trapped by water sprays. This mixture of sand, ash and wastewater then goes to the Ash Lagoon, here," Randy was pointing as he spoke. "The sand and ash settle, and the wastewater drains to the head of the plant. When the Ash Lagoon is full, any remaining wastewater is slowly drained off. We use a backhoe to get it to the drying bed. When the ash and sand dry, we haul it to the landfill."
"Any questions?" asked Randy.
He noticed Mrs. Dunston looking at the clock on the wall and told her, "There's not too much more. We'll go through the Secondary Treatment quickly."
He continued, "Now, in the Secondary Influent Building, the wastewater from the Primary Clarifier is cleaner than when it came to the plant, but still has suspended solids. Suspended solids are particles which are too small to settle," Randy explained.
"This wastewater begins secondary treatment when it gets mixed with returned sludge. The Return-Activated Sludge comes from the Secondary Clarifiers - which I'll get to in a minute. Anyway, the Return-Activated Sludge contains larger bacteria, which consume or eat the floating suspended material in the wastewater. The Oasis or Aeration Basin is where all this takes place, here," he said pointing. "It is a place where the flow is slowed enough that the bacteria or "bugs" have a chance to eat."
"Yuck," said Ali.
Randy laughed and went on, "There are mixers in the basin, that mix oxygen with the wastewater, and keep the combination stirred, so the "bugs" will eat the floating material and not themselves."
"Oooo, Double Yuck!" exclaimed Ali.
Everyone had a good laugh that time, and, then, Randy said, "Moving right along, folks, we have an oxygen system that makes 95% pure oxygen. The oxygen makes the bacteria or bugs in the system eat faster, so the holding time is reduced."
"See," he explained, "our aeration tanks were not big enough, and, there wasn't enough room for bigger tanks, so using this oxygen system solved the problem of holding the sludge for too long a time."
"Next in the process are the Secondary Clarifiers. See, right here," showing them on the diagram, "these work much like the Primary Clarifiers. The sludge is held long enough for it to settle, while skimming off the surface of the tank to catch any grease which may have escaped the primary treatment. The settled sludge can go 2 places. Some of the sludge is kept in the system to have food for the bugs."
"I know, Ali, yuck!" said Randy, looking at Ali and smiling.
"And, some of the sludge is sent to the Secondary Influent Building to mix with the incoming wastewater from the Primary tanks. That is the Return-Activated Sludge I just mentioned. Remember?" Randy asked. "It's used in the Oasis."
They nodded, so he went on, "When the sludge gets higher than 2 feet in the Secondary Clarifiers, the excess sludge is sent to the Dissolved Air Floatation Thickener (DAF) to be wasted. That is called "Waste-Activated" Sludge. The DAF thickener dewaters and thickens the sludge some more. The sludge is then sent to the Aerobic Digester, and the wastewater from the dewatering process is sent to the head of the plant." Randy showed them the way the flow was moving on the map.
He knew that they were getting tired. "You know this is a lot to learn at one sitting," he sympathized, "all we have left are the Aerobic Digester and the Effluent Building."
He pointed again to the diagram. "Briefly, sludge is held in the Aerobic Digester and air is blown in. The sludge is held long enough for about 90% of the 'bugs' to die. It is then pumped to the holding tanks, where the decant wastewater is drained off the top. Decant wastewater is the wastewater that I keep saying is sent to the head of the plant. It has a high nitrogen content, and smells like ammonia.The sludge can then be sent to the farms for land application - which we'll save for another visit."
He went on, "Wastewater goes to the Chlorine Contact Chamber, here, see," once again pointing to the diagram. "There, it has air blown into it, and is chlorinated to disinfect or purify it. Then, it is sent to the Effluent Building. The chlorinated wastewater comes to the Effluent Building by way of a "baffling" system."
"Remember, when we were walking, the water I showed you?" he asked. They all nodded.
"The baffles provide more time to purify the wastewater by chlorination," he said. "At the last baffle, the wastewater is de-chlorinated, so that it can be pumped into the Atlantic Ocean through the outfall pipe."
"Bob said the outfall pipe is a force main," said Rocco.
"That's right," Randy nodded. "It runs from here," he said while tracing the path, "out a thousand feet into the ocean."
"Kids," Sandy Dunston interrupted, "I know we have a lot of questions, but we have to get home soon. Your grandparents are coming to visit."
She looked at Randy as she stood, "Randy, I had no idea how much was involved in the treatment of 'dirty water.' Do you have anything we could read at home to go over what we learned today?"
Randy stood, and led the way down the steps. He said, "As a matter of fact, we do. We have a pamphlet that goes over what I've told you today, plus, it explains our land application program and our laboratory services. Those were things we didn't have time to discuss." He added, "It even has a copy of the diagram we've been looking at."
They were back in front of Jeannette's counter. "Jeannette, could you give Mrs. Dunston one of our brochures?"
"Here you go," Jeannette, said as she handed the booklet to Sandy.
"If you have any questions, after you read through it, give us a call," Randy said, as he opened the door for them.
"Rocco, Ali, tell Randy 'thank you' for giving us such a good tour,"
"Thanks, Randy!" said Rocco.
"We really learned a lot." Sandy added, "Tell Bob and Charles we appreciate their time."
Ali piped up as she was almost out the door, "Tell John Britt thanks, too. Bye, Jeannette! See ya."
For More Information:
Town of Ocean City
6405 Seabay Drive
Ocean City, MD 21842