More Data Crunching

So, today has been a little bit topsy-turvy because the President (of Bangladesh) died yesterday (aged 85) and so there has been an impromtu public holiday...but so impromptu that some places are taking time off, and others aren't.  Thankfully we managed to get the samples over to the icddr,b and had a good chat with Dr Zahid there.

He's got some initial results from the first and second tests (raw sludge and 5 day-matured sludge) and we're seeing a factor 10 reduction in E-Coli and C. Perfringens.  I'll graph the results and get them up asap.

Suman also told me that while they were taking samples, the sludge was so hard it was breaking the (disposable, plastic) spoons they were using to collect material.  What this says about the quality of disposable cutlery here, versus the dryness of the sludge I don't know, but I reckon that's a good result - we can dry sewage slop to a hard cake in 5 days, with a meaningful reduction in pathogens.

I've also been looking at the temperature differences in the three beds, compared to those measured from our weather station (on the top of a bamboo pole next to the site):

This will probably be too tiny to read on the blog, but the green line is the bed that was vented for 12hrs during the day, and closed at night, the red line is the bed that was vented 24/7, and the blue line was our control, the open bed.

The spikes occur in the mornings, between 7am and noon, and the flat-ish bits between them are around 2pm-3am.  This means there is the greatest difference between outside and inside (the roofed beds) in the morning, indicating that they are gaining heat rapidly once the sun rises, and also, they are retaining heat overnight.  The last three or four spikes are where we closed the green-line bed 24/7, so it was basically a greenhouse, and you can see it was retaining more heat at night, and performing marginally better that the open bed during the day.

I'm not sure why the vented bed also improved its performance over the last few days, and I will ask Practical Action if they did anything to the roof during this time.

Anything from the minibar?

If anyone asks, I've got some SOIL SAMPLES in the fridge...

Taking them to the icddr,b later today - they might even have some initial pathogen testing results for us too - so much excitement in 24hrs!

Phase 2 Initial Results

So, I've had the data for an hour or so this evening, and this is what we've got:

We've got some interesting step-up effects going on with the beds with roofs on (red and green lines), whereas the open bed (blue) is tracking the external weather conditions (purple) pretty faithfully.  The weather station is about 15ft up on a bamboo pole, hence it's a few degrees cooler than 6" above the sludge which is where the temperature sensor was hung.

The green line is from the bed where we had it open during the day, and closed at night, and on the 17th we switched to having it closed 24/7 to try and 'bake' the sludge.  It does seem to have lifted it a few degrees above the fully vented approach (red line) for these last few days, but I'm not sure its a conclusive difference.

Also, we hit the magic 55 degrees for a few hours which is pretty exciting!

And check out how closing the roof at night keeps the beds up to 5 degrees warmer than leaving them open...

The more I look at this the more I think I may need to tweak my trendlines...when you look at them individually, the step-up effect is much more pronounced once we closed the roof 24/7...

Anyway, it all looks good to me so far.  More analysis tomorrow.

Hotels and hartals

We've got hartal's Monday, Tuesday and Thursday this week.  Which basically means I can't leave the hotel, or at least definitely not the immediate area.

So, I've been entertaining myself catching up on emails, clearing out all those old ones at the bottom of my inbox, and updating the blog!

What do you think of the new layout?!  I've still got some gremlins to sort out, but it's a bit more glamorous than it was.  I'll keep tinkering over the next few days, so keep checking back to see it's latest incarnation...

UPDATE: Wednesday 20th March

Back in the office today, and waiting for the car to come back that's gone to collect our last round of samples and data from the site.

We've asked the guys from Practical Action to do the sampling for us, and they are going to bring the samples and equipment half-way back to Dhaka, where a WaterAid driver is going to meet them and bring it all back to the office.

 As I've been away from the site for most of this test, I can't wait to see what information we've got on the temperature and weather sensors!  I'm consoling myself that my forced absence means that we've inadvertently done some capacity building with the PA staff, as they now know how to undertake the sampling process and could feasibly do it without our instruction.

It'll still be a couple of weeks before we get the pathogen results back from the lab at the icddr,b so we won't know about pathogen reduction for a while, but it'll be great to see if the higher (anticipated) temperatures have had an effect.

I'll report back with some initial results later today.

Round two - halfway through

Sunday 17th March

Its a public holiday today (one of the 24 they'll have this year!) - to commemorate the birthday of Sheikh Mujibur Rahman, 'Bangabandhu' ('Friend of Bengal').  He is seen as the father of the nation, and his eldest daughter is the current prime minister.  More info here: http://en.wikipedia.org/wiki/Sheikh_Mujibur_Rahman.

Suman has been a trooper and gone down to site today to collect another round of samples (so we can track pathogen decay after 5 days and 10 days) en-route to another project site.  The driver returned to Dhaka with them, and I've just put them in the bath!

 I was going to unpack them and put them in the fridge, but the ice is still pretty thick, so I'll let them melt quietly overnight and drain off any excess water in the morning, before we take them to the icddr,b.

I sketched up a little sampling plan for Practical Action last time I was there, and this gives a pretty good idea of the current site layout (numbers correspond to sampling points):

Computerised version of sampling plan sketch

Apparently, the open bed is the most liquid of the three (open/ roof+vented/ roof+closed at night) and the middle bed, which is open at both ends, is almost dry! It's only been 5days, and they each have 900L of sludge on them, compared to 500L in the previous Phase!  This is Good News.

They are all still dripping a bit at the gate valve, showing water is still draining out of them, and apparently some was also coming out from the end of the reedbed, so the 13th sample was taken too (I suspect this is because the reeds are still very young and the bed is still maturing).

They have been raking every day before 9am, when the temperatures in the bed are closest to outside temperatures (to minimise heat loss when the roofs are removed), and perhaps in the next (and final phase) we will try non-raked versus raked to assess how much impact it has.

We are now trying a 'baking' approach and closing the end of the bed that was being closed just at night, but now keeping it closed 24/7 to assess the temperature gain from having a sealed drying bed.

We've got hartals ('closed doors') tomorrow, Tuesday and Thursday.  They are basically national strikes, making it hard to get out and about, and it's inadvisable to go out after dark in case anything (riot-y) kicks off.  This means I'm making a bid for Faridpur on Wednesday so I can get there again before I leave on Friday!  I'll keep you posted on whether I make it back before the city shuts down!

A Weekend in Dhaka

Friday 15th/ Saturday 16th March

I did my (now) usual Friday walking tour with the Urban Study Group.  I was excited about this one as we were going to see the waterfront - a part of Dhaka I've never actually dared venture to!

Waiting outside Sutrapur Police Station for the group to assemble, you can already see bits of old rubbing up against the new...

 After setting out from the  Sutrapur Police Station we first visited the Reboti Mohan Das Residence, the palatial building built in Neo Classcal style which used to overlook the famous canal of Dhaka the Dholai Khal. Unfortunately, the canal was filled up less than 20 years ago, and is now a barely used road (I'm not sure it actually goes anywhere).

 

Reboti Mohan Das Residence

Reminded me of my red and cream bike at home...

 The house is now used by the Dhaka fire service (or equivalent) and used to home about 60 families of its employees.  In one way it's nice that it's being used, but it would be an incredible tourist attraction too!

We then visited Kalicharan Shaha Street. The most unique feature of the Mohalla is that, it has experienced very little change, most of the buildings from the colonial period have survived so far.

Now a kind of college residence

Internal courtyard of the residence

Detail of relief tiles originally made in Calcutta

Detail of the woodwork

The top of the building says '1915 Mongol Alaya'

We then walked through a market and some paper recyclers!

Recycling in full swing

The dust in the air made it hard to stay for long - we soon started coughing and spluttering - goodness only knows how they tough it out.

The main highlight of the walk was Ruplal House,the waterfront palace, which has been converted into a vegetable/spice market and Lalkuthi.

The market makes it almost impossible to take a full-frontal photo of, but here's one I found from the 19th Century, of what it used to look like:

And bits of it now:

The rusty roofs are the spice market which have taken over the ornamental gardens

The internal courtyard

 The current waterfront:
 

Had a lovely (late) lunch at the American Club with a fellow walker, and crashed out at the hotel after a tiring day in the heat of the city.

Saturday was mainly chilling out at the Nordic Club spa with a friend from the garment industry, getting our nails done and remember what it is to be clean and girly!

Back to poo tomorrow...

A useful day in the office

Thursday 14th March

On Thursday I was working in the WaterAid office, and in the afternoon presented the project to our colleagues there.

It was good to share the project with others, particularly as we now have a growing team working on the project.  We have a new project officer, and a lady working on some of the social aspects of the project.  Along with Suman and Opel, that now makes four in WAB.

It was also useful as Mamun and Dipok from Practical Action joined us, and we discussed several further design developments:

Rubbish Net:  Unlike our previous sludge from Phase 1, this sludge was full of detritus, bits of plastic and general rubbish.  It wasn't obvious when they collected the sludge, but as it settles in the drying beds, the rubbish is floating to the top.  We talked about pouring the sludge into the beds through a coarse net to capture the rubbish, which can then be dumped in a pit on-site to degrade safely.  This may also mean we do not need a splash plate, but we shall see.

Lightweight Roof:  With all the additional framing, the roof is now found to be too heavy, and a more lightweight design is to be explored.  Mamun has spoken with some of the local CNG drivers, and the polythene they use for their windshields is thought to be good - tough and won't rip.  So, amusingly, seeing as this was something we suggested way back in the beginning, it looks like we might end up with a poly-tunnel after all!

Scaling and sizing:  We have sought to develop a modular design that can be scaled up to suit demand.  The beds themselves will be relatively easy to scale, but now we have the reedbed element, we will need to be careful it doesn't get too large.  However, I am not convinced that we really understand what volume of water is draining out of the sludge - reedbeds are based on an average daily flow - and as we have an exponentially dropping flow over time, we used the worst-case first 24hrs.  However, as the reedbed works with a plug-flow, I am now wondering whether we could have used a smaller version, and taken the total expected volume, and divided it by the number of days...The issue then being, what proportion of water drains out and what is evaporated.  perhaps next time, we will focus more on moisture content, and measure the initial moisture content more accurately, along with the total volume drained.

Sludge temperature:  As our initial question was around which roof generated the most heat underneath, we have been measuring air temperature over the sludge, rather than the actual sludge temperature.  We have been assuming that air temperature is a useful proxy.  However, it would be good to now understand more about the actual sludge temperature relative to the air temperature.  Practical Action said they had some sensors they could use, so we might try this for the second half of the test, and definitely for Phase 3.

Volumes of sludge:  The team working in Khulna are keen to bring the drying beds to their town, but before we can do that, it was suggested that they need to get a better idea of what volumes of sludge they will need to be treating, and how often.

Soil testing:  We need to get the now composted material from Phase 1 tested, and arrange for the material from this Phase 2 to be tested too.

So, still more work to do before we get to a final design, but each time we run the test we are learning more, and gaining experience, so I do not think any of our efforts will have been wasted.

Sample Time

Tuesday 12th March

I should say that while we are in Faridpur this time, we have been staying at BRAC’s lovely guesthouse in the grounds of its regional training centre.  While we were there, 160 people were using its facilities, in various groups from government officials to villagers, receiving training on a wide variety of topics, I forget the detail but BRAC work across many many sectors, including WASH (water, sanitation, hygiene), environmental legislation, and womens’ empowerment.

 Lovely grounds at BRAC Training Centre

  

It’s been going 22 years, and still going strong.

Wonderful flower garden in front of the guest house – big pom-pom headed chrysanthemums, poppies, sunflowers, aloe vera, and many others I couldn’t name.

We went to site, the morning after [the sludge delivery] the night before, and all seems well.

Sludge in the open bed - we're monitoring the temperature just above it to compare with the ambient weather monitored from the weather station mounted on a bamboo stick 30ft in the air.

Here you can see the corkboard wedges tilting the roof slightly to allow rain/ condensate to run-off.

On one of the roofs, we are leaving the ends open 24/7, and the other, we are closing between 6pm and 9am to understand more about the effect of ventilation on the drying rate.

View of the beds with their new roofs on

We then began the raking and the sampling

Mmm raking sludge

Suman helping with the sampling

This is my brave face.  Note the bewildered local watching through the fence...! 

This one’s probably better - 'happily spooning sludge into a jar'

We had a bit of an issue with the first drying bed (the one nearest the entrance) because when we opened the gate valves, at first clear water came out, and then nothing...

Initial result – number 12 is from the bed in question, and made us suspicious

No flow from the third pipe was worrying

This suggested to us that some water had remained in the bed from when they were testing them (when they were newly built, and before the application of the sludge) and now there was some kind of blockage somewhere.  We poked rods and sticks into the gate valve, and even melted a hole into the connection pipe to the bed so we could measure levels in the pipe behind the valve, but couldn’t find anything conclusive.  Mamun (Practical Action) was sure the valve was working fine when they tested it, so we thought it might be the material on the filter blocking it.  We gave it a thorough raking over, and sure enough slightly mucky water started to drip through.

Suman had an ingenious way of getting the effluent samples from the valves – involving the use of plastic plates…

Plate underneath valve to catch flow

Plate folded and used to pour liquid into the sample jars.

One interesting observation was the build up of condensation on the underside of the roofs.  I couldn’t quite capture it, but it formed a kind of gradient from south to north, with the south end having almost no condensate, and the north end being very fogged.  Funnily enough this aligns with the prevailing wind direction, so perhaps our alignment was out so much after all! (we wanted them E-W orientated to catch maximum solar gain).

One we were done at site, we went back to the Practical Action office to pack the samples on ice for the night.  We'd take them to Dhaka in the morning.

Slabs of ice being delivered

then smashed up

and then packed around the samples

Its Poo-time!

 Tuesday 12th March
I wasn't allowed out last night due to ongoing troubles around the death sentence recently given to Delwar Hossain Sayeedi (convicted on charges including murder, rape and torture during the war of independence in 1971).  There are basically hartals in force every few days which mean you're not allowed out on the streets (technically) and its particularly risky at night.  So I gave my camera to the trusty Suman (WaterAid) who along with Mamun (Practical Action) played photographer for me and told me all about it in the morning.

The sweepers being issued with their PPE - aprons, gloves, masks and boots

Collection Team

Doing their job.

The filter beds are just the right height for the truck, it's almost like it was designed that way...

You know how I said the filter beds looked nice and clean...

Not for long!

We managed to keep one half of the roof on, and not splash it!

Teamwork

New sign too!

 

Putting the sludge to sleep for the night in its new bed.

More updates soon!

New roofs!

Monday 11th March

It was the (now) usual trip down to Faridpur, and once we arrived we went straight to site.  The team at Practical Action have been working flat out to get everything ready in time for my visit, and they’ve done really well. 

Final adjustments being made to the new roofs at Practical Action HQ in Faridpur

We have a new reedbed installed, and the old filter beds have been emptied into new ones retrofitted onto the old flat-beds:

New reedbed with retro-fitted filter beds in the background

Baby reeds (cannas?)

New reedbed with tiny pencil thickness holes going into it that you can barely see at the bottom edge of the chamber…hopefully we won’t get them blocked!

New gate valves to control the flow out of the filters

The new height of the beds is partially to get the levels right for drainage into the reedbed, but also to aid delivery from a lorry bed rather than on foot.  They have a wide section to allow the truck to pull up next to the bed, and the barrels can then be tipped in directly, rather than needing to be lifted off onto the ground. We also have a new splash-plate resting on the top of the filter – a concrete 1.5ft x 2ft square pad – to minimise disruption to the sand layer when the sludge is poured in.

It looks so clean and tidy....

The office is taking shape and has a nice veranda to view the sludge drying from:

The new site office under construction

The treated sludge from last time is now resting in various states:

Sludge from the filter beds mixed with ash (grey pile) and sawdust (brown pile)

Sludge from the flat beds, not mixed with anything

We are now arranging to get some soil testing done on these to assess their nutrient value as compost (sulphur/ potassium/ nitrates/ phosphorous).

After looking at the new 2-part roofs, polycarbonate sheets bolted onto steel frames, it became clear that they are basically flat boxes with joins in. 

Roofs being delivered to site (I realise the irony of them being delivered by bike while our fancy NGO SUV sits idle in the foreground…!)

New box-section roof, with sliding end panel to adjust ventilation

This new flatness will not be good for directing rain off the sludge, or allowing condensate to drip away.  We considered building a small 1” lip on the eastern edge of the drying beds to aid runoff.  It would be preferable to have them tilted north-south, but this means runoff would have to travel the length of the bed, rather than the width, and there is a join across the middle – another learning point about making sure the orientation is right!  We started building this lip out of concrete, but in the end decided the quickest option would be to use corkboard (the stuff the firmer crashmats used to be made of in school gymnasiums) cut into strips and wedges to provide the required height and insulation.

Finally, we tied on the temperature sensors  to the roofs at 16:30, and made sure everything was in place and ready for the upcoming sludge delivery.