l********u
发帖数: 823 | 1 I recently started a thread on Yahoo's Water Forum that I've been
subscribing to. The discussion is getting interesting. I'm going to post my
original message as well as a few replies for those of you who are looking
for interesting stuffs to read during the lunch break.
Also, if you have any ideas, thoughts about the WWTP disinfection problem,
please let me know. We are going to meet the plant operator and lab team
next Monday.
|
l********u
发帖数: 823 | 2 Original:
Dear all,
I am a consulting engineer. Recently, one of our clients, owner of a WWTP,
reported a noncompliance issue that we have been trying to solve. This WWTP
has been operated since 1996. Everything had been running ok. However,
starting from the summer of 2007, they detected sporadic outbreaks of fecal
coliform at the discharge point.
The treatmet process is quite conventional (primary-activated sludge-
secondary clarifier-disinfection). One thing that's unique about their
disinfec |
l********u
发帖数: 823 | 3 A reply:
My recommendation would be to question the need of disinfection, especially
with chlorine, which has proven to form chlorinated organics or also called
DBP (Disinfection By Products). When EPA implemented the CWA in 1972 it
also set a standard for bacteria and everybody started to use chlorine, as
testing for residual chlorine is cheap. This however introduced chlorinated
organics, among them THM's (trihalomethanes) in our open water, used for
drinking water. EPA recognized the problem |
l********u
发帖数: 823 | 4 One more:
Peter,
I don't understand why you question the need for disinfection. Is there a
paper or other documentation from the CDC or GAO in the 70s that you could
send to me?
It is my understanding that the predominant literature suggests that fecal
coliform and E. coli are used as indicator bacteria to determine to degree
of contamination by fecal matter. The presence of fecal matter indicates
the potential presence of any number of harmful (and sometimes deadly)
pathogens. Children and |
l********u
发帖数: 823 | 5 3rd:
Personally I think any form of disinfection of treated sewage is a waste of
money and when we apply disinfection (also on drinking water), we should
first accept that our original treatment (removing all solids) was not 100%
effective, so we need a post-treatment. Secondly we should know how this
disinfection really works, with other words how does it kill bacteria. UV,
as mentioned in the literature, destroys the DNA of cells and thus kills
bacteria. To do so it must penetrate the cell w |
l********u
发帖数: 823 | 6 4th:
First and foremost, this plant should not be dumping sewage effluent
directly to public waters because it carries a heavy load of complex
chemical compounds of unknown toxicity and synergistic effect. A review of
USGS and academic literature searching with hormone - estrogen - EDC will
reveal the enormity of this problem. The brain development of your children
and your own masculinity are clearly endangered by drinking from waters that
carry this effluent because municipal filters are not c |
l********u
发帖数: 823 | 7 There are about a dozen replies, including a few back and forth arguements
between three people. If you are interested in reading them all, let me know
. :) |
j*******o
发帖数: 102 | 8 I don't think your problem is related to DBP. My best guess is the chlorine
loss withing the 12-mile main (what's the residence time?) due to
nitrification (need to check the ammonia level in the source water). Once
the chlorine disappears, there will be biological regrowth problems,
especially in wastewater. |
l********u
发帖数: 823 | 9 我们这个client的问题确实跟DBP没关系，但是由此引发的一些讨论跟DBP挺有关系的。
让人觉得这个世上真是有不少坐者说话不嫌腰痛的人。或者说是一些工业出于私利，雇
用些有PHD学位的人混淆大众。
In case you are interested, the residence time in the force main is about 12
hours. The level of ammonia-N at the discharge point was in the range of 0.
3-1 mg/L.
chlorine
【在 j*******o 的大作中提到】
: I don't think your problem is related to DBP. My best guess is the chlorine
: loss withing the 12-mile main (what's the residence time?) due to
: nitrification (need to check the ammonia level in the source water). Once
: the chlorine disappears, there will be biological regrowth problems,
: especially in wastewater.
|
V*******7
发帖数: 53 | 10 有具体的文献或则试验数据支持“ Once the chlorine disappears, there will be
biological regrowth problems, especially in wastewater”吗，尤其是对于FECAL
COLIFORM而言？ 个人觉得regrowth的影响因素太多了，光看chlorine level恐怕偏颇。
chlorine
【在 j*******o 的大作中提到】
: I don't think your problem is related to DBP. My best guess is the chlorine
: loss withing the 12-mile main (what's the residence time?) due to
: nitrification (need to check the ammonia level in the source water). Once
: the chlorine disappears, there will be biological regrowth problems,
: especially in wastewater.
|
|
|
a*****a
发帖数: 1038 | 11 Hi Man,
If possible, please give me a big picture of this WWTP process diagram. I
assume the standard P&ID
Primary clarifier --> Secondary clarifier (activated sludge) --> sand
filter --> disinfection chamber --> dechlorination chamber --> 12-mile force
main to the river.
First question, what's the chlorine demand for effluent leaving the
secondary clarifier at chlorination chamber?
Second question, Do you have any baffle walls in the disinfection chamber?
I guess you probably do not have baffl
【在 l********u 的大作中提到】
: I recently started a thread on Yahoo's Water Forum that I've been
: subscribing to. The discussion is getting interesting. I'm going to post my
: original message as well as a few replies for those of you who are looking
: for interesting stuffs to read during the lunch break.
: Also, if you have any ideas, thoughts about the WWTP disinfection problem,
: please let me know. We are going to meet the plant operator and lab team
: next Monday.
:
|
a*****a
发帖数: 1038 | 12 I really could not understand your process flow based on your description.
I believe any WWTP has to dechlorinate the water from disinfection chamber
prior to leaving the plant through 12-mile force main to the river.
Otherwise, fish in the river will be killed.
Also, 0.3 - 1.0 mg/L as Total-ammonia or free ammonia ??
The best ratio of chlorine / ammonia is 5:1
12
0.
【在 l********u 的大作中提到】
: 我们这个client的问题确实跟DBP没关系，但是由此引发的一些讨论跟DBP挺有关系的。
: 让人觉得这个世上真是有不少坐者说话不嫌腰痛的人。或者说是一些工业出于私利，雇
: 用些有PHD学位的人混淆大众。
: In case you are interested, the residence time in the force main is about 12
: hours. The level of ammonia-N at the discharge point was in the range of 0.
: 3-1 mg/L.
:
: chlorine
|
l********u
发帖数: 823 | 13 Primary clarifier --> Secondary clarifier (activated sludge) --> sand
filter --> disinfection chamber --> dechlorination chamber --> 12-mile force
main to the river.
(Should be Primary clarifier --> Rotating Biological Contactor (don't ask me
why they put a RBC there. It was designed and built in 1993 and upgraded in
1996) --> Secondary clarifier (activated sludge) --> Chlorine added --> 12-
mile force main --> dechlorination --> discharged to the river)
First question, what's the chlorine deman |
a*****a
发帖数: 1038 | 14 (Not sure about the chlorine demand. I've designed a 12 hr bench test to
measure the actual demand of the supernatant taken out of the secondary
clarifier. They've been adding 8-10 ppm of chlorine to the effluent after
the 2nd clarifier)
(no chamber. Disinfection is done in the force main)
Disinfection in the 12-inch force main seems to complete mixing and
eliminate the short circuiting flow. I think you request the plant
discharge flow rate from plant operators and determine the detention time |
l********u
发帖数: 823 | 15 Disinfection in the 12-inch force main seems to complete mixing and
eliminate the short circuiting flow. I think you request the plant
discharge flow rate from plant operators and determine the detention time in
the pipe. Bench scale test will not help you in this case to determine the
chlorine demand unless you can using the existing force main as the coupon
test. It is very possible that biofilm has been built up inside the 12-inch
force main to eat the chlorine residual. In addition, what typ |
a*****a
发帖数: 1038 | 16 (We will inspect the site on Monday and look at the corrosion problem, along
with other issues such as infiltration, etc)
Infiltration ?? - for me, it seems to be made by prestressed concrete
cylinder pipe (PCCP). There are several service companies could identify
the pipe leaking by accoustic technology. |
