Natural Perspectives -- Vic Leipzig and Lou Murray

Vic Leipzig and Lou Murray

At first blush, it’s a horrible thought. Not only is the Orange County

Sanitation District pumping 250 million gallons a day of partially

treated sewage into our ocean, now they’re thinking about adding bleach

to the effluent. This doesn’t sound like a good idea. Or is it?

Sure, if we poured bleach directly onto the starfish and sea urchins

that live in the ocean, it would kill them. But bleach isn’t like the

energizer bunny. It doesn’t just keep going and going and going. It’s a

chemical compound called sodium hypochlorite and, in performing its job

of disinfecting, it is depleted. Used up. Inactivated. Or at least most

of it is inactivated.

And that is the problem. Theoretically, the bleach will inactivate

itself as it is used up in the disinfection process. By the time the

sewage reaches the end of the outfall pipe five miles out to sea, two

things are supposed to have happened. All the bacteria should be dead and

all the bleach should be inactivated. But that’s only if the treatment

process worked perfectly. In reality, neither goal is completely

achieved.

If the technicians add too little bleach, not enough bacteria will be

killed. If they add too much, the excess bleach is discharged into the

ocean. To solve this problem, districts that use bleach use very high

levels of bleach to kill as many bacteria as possible, and then they add

sodium bisulfite to neutralize the excess bleach.

Another factor is that the bleach must remain in contact with the

sewage for a certain amount of time prior to inactivation in order to do

its work of disinfection. This treatment method requires precise

calculations in an imprecise system.

Even after treatment, sewage is still loaded with organic matter and

bacteria. Some of that organic matter is in clumps. Bacteria and viruses

inside those clumps will be protected from contact with the bleach and

won’t be killed. There may no level of bleach that will guarantee 100%

effectiveness at killing bacteria. “Enough” bleach may be impossible. And

some harmful excess bleach can always slip through, so “too much” bleach

is practically inevitable. The perfect balance cannot be struck.

Adding disinfectant chemicals to sewage to kill bacteria isn’t new.

Some sewage treatment facilities already use bleach. Others use chlorine

gas to kill bacteria. Chlorine gas is even more effective than bleach.

According to the US Environmental Protection Agency, properly done

chlorination of sewage will kill 99% of the bacteria. Unfortunately,

chlorine has some nasty drawbacks. It’s a toxic gas, and nobody is happy

about having large truckloads of it make regular trips through their

neighborhood on the way to the treatment plant. Worse yet, the chlorine

can react with organic compounds in the sewage to produce chlorinated

hydrocarbons, which can cause cancer.

We’re not in favor of using either bleach or chlorine because of the

potential for harm to marine life. There are alternatives to these

disinfectants. Ultraviolet radiation and ozone are treatments recommended

by the Environmental Protection Agency in areas such as Huntington Beach,

where discharge of chlorine or bleach in treated sewage might harm fish

and other marine life. These treatments have the significant advantage

that they act effectively against viruses as well as bacteria. Many

viruses cannot be effectively inactivated with bleach.

Use of ultraviolet radiation or ozone generally requires a higher

level of pretreatment of the sewage prior to disinfection. Conventional

secondary treatment can do the job, but there is an even newer technology

called microfiltration. This technology filters out very small particles

and thus reduces the overall particle size in the effluent. Because

bacteria and viruses inside particles are resistant to disinfection,

microfiltration greatly improves the effectiveness of disinfection by

removing the larger particles. After microfiltration, the effluent would

be ready for the ultimate level of sewage treatment, tertiary treatment.

This treatment level produces effluent clean enough to be used as

“recycled” water for watering golf courses, parks, highway medians, and

other nondrinking uses.

Water is a precious resource. Our current sewage disposal practices

not only pollute the marine environment, but they waste hundreds of

millions of gallons of fresh water each and every day. We can do better.

We can’t afford not to.

* VIC LEIPZIG and LOU MURRAY are Huntington Beach residents and

environmentalists. They can be reached at o7 [email protected] .