James Boyle needed 12 stitches in his cheek to close a wound which almost cut through to his gum after he was attacked by two men with a craft knife.
The 42-year-old, who is now waiting to hear if doctors can repair some of the damage with plastic surgery, said he may be too terrified to return to his job.
Mr Boyle said his injuries had left him “devastated” while he suffers flashbacks of the brutal assault, which took place as he patrolled the site shortly after midnight on Sunday.
Mr Boyle, who has worked at the site for nearly 12 years, said: “I was on night shift working 6pm to 6am and was doing the rounds to check some generators when these two intruders attacked me. I had obviously surprised them and felt like I was punched at first. They ran off, and I quickly realised it was something more serious.
“I could feel blood pumping out of my head from a deep wound. I started to stumble away in terrible pain to try toget back to my control room. Every time I wiped blood away, more would come back and fill my eyes so I couldn’t see. It was like a windscreen wiper.
“I managed to get back to the control room and locked the door. I was panicking and there was so much blood. I was scared because I didn’t know how badly injured I was.”
Mr Boyle managed to call an ambulance and paramedics rushed him to Edinburgh Royal Infirmary where he received 12 stitches to his cheek and another six to a head wound.
He added: “The doctor told me he wasn’t going to lie for me, I would be scarred for life. I don’t want to give myself false hope and think it will get a lot better. It’s hard to look in the mirror, and my kids don’t mean it but they find themselves staring at my injuries. I really don’t know if I can ever go back to work. I just keep remembering what happened. I don’t even want to leave the house.”
The main suspect is described as white, 5ft 10in to 6ft 2in tall, slim build, late 20s to early 30s, short light/fair hair, a gaunt appearance. He wore a green camouflage jacket and blue faded jeans. The other suspect is described as white and between 5ft 8in to 5ft 10in tall.
Mr Boyle, who lives in Bathgate with partner Linda Russell, 39 and children Angela, 20, and Connor, 13, said: “The police told me they found discarded fuel cans so they think the men were trying to siphon off diesel from temporary generators. I was on-site alone so if I had been more seriously injured and couldn’t move then it could’ve been fatal.”
A police spokesman said: “We are appealing to anyone who was in the area of the Seafield Sewage Works in the early hours of Sunday morning, who saw two men acting suspiciously there, to contact police.”
A spokesman for Veolia Water, which runs the sewage works, said: “Our thoughts are with the member of our team who was injured in this attack.”