2010

Exam no: 115909

2/21/2010

Lay Out of a Septic Tank

Construction Studies Portfolio

2

Foreword

This document has been compiled by Ciaran Henderson as part of his 6th year construction studies

course, all rights reserved®. If you would like to find out more about Ciaran;

His LinkedIn Profile:

His O-Desk Profile:

3

Contents

1. Project Planning Pg4

2. Research and Investigation Pg6

3. Design Of Artefact Pg11

4. Realisation-Manufacture of Artefact Pg15

5. Evaluation Pg21

6. Experimental Work Pg23

7. Appendix Pg29

4

Project Planning

Introduction to project-

I plan to do primary research by talking to my father as we had a septic tank installed

in 2005 and i plan to investigate whether or not the plans he had would be satisfactory

to base my project on.

I plan to do secondary research on the internet to find out about different kinds of

septic tanks & their different uses.

Aims & Objectives for project-

I aim to achieve an A1 in my project to go towards points for my Leaving Cert.

I aim to have a greater understanding of how a septic tank works so then i can apply

this to my exam if this area comes up.

I aim to apply my skills of planning, organizing and controlling to achieve the best

possible effect that my project makes.

Time Management Strategy-

Septemeber→October: Planning stage

October→February: Construction stage

February→April: Write up stage

Time Management

Write Up

Construction

Planning

5

Budget & Material Constraints-

Wood- Woodwork room for large pieces & home for offcuts.

Plexiglass- Construction room.

Insulation- Left over offcuts from attic conversion at home.

Gravel- Spare bags are in the shed at home.

If required io have allocated €25 for additional materials.

6

Research & Investigation

Analysis of project-

Project Brief:

My objective in this project is to create a 1:100 scale model of a septic tank,

percualation area and my adjoining house. The purpose of the house is to show the

septic tank and perculation area in perspective to it. Because of my project i hope

people will learn from it and gain a greater understanding of septic tanks.

Information needed:

-An understanding of how a septic tank works.

-Information on how to install a septic tank.

-Dimensions of the layout of the septic tank & perculation area.

-Dimensions of a house to compare the septic tank with.

Theoretical Investigation of project area-

How a septic tank works:

1. Sewage enters via the inlet T pipe and

discharges to the lower of the tank.

2. Gravity pulls the solids in the sewage to

the base and via anaerobic biological

action, a scum layer can form on the

surface.

3. Effluent (with a very low solids

content) leaves via the outlet T pipe.

This can then enter a second or third

chamber and then leads to a soakaway

field drainage system(percolation area)

7

Types of Septic tank systems:

Gravity septic system

This is the basic system septic system used.

Wastewater enters the septic tank at the T-inlet,

the sludge settles in the tank and the scum floats

to the top. The effluent then flows out of the tank

to the drainfield/Percolation area.

Septic tanks may have one or two compartments .

two compartments do a better job at settling solids

and are required for new systems.

Tanks need to be emptied every 3-5 years,

depending on the tank size, the amount and type

of soilids entering the tank.

Early warning levels inside the tank-

-The bottom of the scum layer is within 3 inches of

the bottom of the outlet tee or baffle

-the top of the sludge layer is within 12 inches of the

bottom of the outlet fitting.

The percolation area is a network of

perforated pipes laid in gravel filled

trenches. Effluent trickles out these

pipes, through the gravel

& into the soil. The

size and type of each

depends on the daily

wastewater flow &

soil conditions.

8

Pressure distribution septic system

This is used in areas where the conventional

system cannot ensure safe water treatment. It

allows for-

1) Resting cycles.

2) Equal distribution of effluent.

3) Shallow placement of drainfield.

This system works essentially the same way

as the Gravity system, other than it contains

another chamber with a pump that

electronically controls the flow of effluent to

the drainfield. It does this using “control

floats” when they reach a certain level

specific amounts of effluent are released.

This system also has an alarm float

that when levels get too high in the

tank it alerts the household, this

prevents a build up of dangerous

gasses and stops overflowing saving

costs on emergancy call outs.

Mound septic system

These are essentially the same as a

pressure distrubution system other than

the percualtion area is rasied up on a

“mound” of sand with a gravel filled

bed.

These are used in areas where the

ground is not suitable enough for

drainage and so is raised up. This gives

the effluent a greater distance to travel

before reaching groundwater.

9

Sand septic system

These are essentially the same as a pressure

distrubution system other than the extra

sand filter which allows for a high level of

wastewater treatment.

The sand filter is filled with specific sand

material, a network of pipes is placed in a

gravel-filled bed ontop of the sand. The

septic tank effluent is pumped under low

pressure through the pipes in controlled

doses to insure even distribution. The gravel

underdrain then collects the effluent and it

travels to either a second pump for

discharge or to a gravity flow drainfield.

Aerobic Treatment Unit

ATU’s are similar to standard septic

systems in that they use natural processes

to treat wastewater. But unlike

conventional systems, ATU’s also use

oxygen to break down organic matter.

These units have a main compartment

(aeration chamber) in which air is forced

and mixed with the wastewater. This

creates an environment where bacteria

are free-floating in the liquid and grow as

they digest the solids.

Many units include a second chamber where

solids, that the bacteria are unable to digest,

settle. The two chambers are connected, so these

undigested solids can be returned to the aeration

chamber, either by gravity or a pump. It is this

process of return and mixing that is important for

effective operation.

10

AdvanTex-AX Wastewater Treatment System

Instead of using sand

or gravel for the

filtering media, the

AdvanTex product

line uses an

engineered textile.

Textile is much more efficient than sand or gravel

because it has about five times more surface area. That's

why, with textile filters, you can treat the same amount

of wastewater in a fraction of the space.

Drip irrigation

This is a shallow, pressure-dosed system that equally

distributes pre-treated wastewater at a slow rate over

the entire drainfield, preventing saturation of the soil.

This is not so much a septic tank than a way to reuse

wastewater from a source such as septic tank effluent. This is

a very effective way to use wastewater as leveling the field is

not nessesary, you have the ability to irrigate irregular shaped

fields & there is a lower labour cost in maintaining this system.

11

Design of Artefact

Design idea for artefact-

My inspiration for this project came from my personal life experiences.

In October of 2000 me and my family moved into a new house in newtownmountkennedy,

Co. Wicklow. The house at first

seemed fine, just in need of a few

minor repairs and spruce ups, however

we soon discovered that the toilet was

backing up due to a horrible

“homemade” septic tank that was

installed when the house was built.

Because of this the toilets kept backing

up and there was a terrible stench both

outside and inside the house. We had

to replace this with a brand new septic

tank system at a cost of about €10,000.

The construction of this new septic tank took over 3

months to complete and the contracters had to dig up our

entire back garden to install it. The septic tank itself was

about 10ft in height and had to be lifted into place with a

crane.

The first step in the construction process was to dig a test

hole to determine the drainage ability of the garden. After

this was completed they could begin to dig the

trenches for the perculation area and the hole for

the septic tank.

They then laid gravel into the trenches for the

pipes and in the excavation for the septic tank and

around the tank. These trenches were then covered

over and buried. The septic tank was then

manovered into place in the ground, and buried

other than the diffusion inspection chamber for the

settlement chamber and the inspection chamber for

the air compressor.

12

My original idea was to do a cut-through section of a septic tank and show all the inner

workings of it.

However i decided against this as i

could not visualise the end reslult

or see what materials i would

require to carry out this kind of

project. I also thought it would end

up being quite intricate and small.

My next idea was to do a 1:1 scale of a perculation pipe and

surrounding area, show all the different aggregate layers and

the different distances required to achieve good drainage and

to meet regulations. However i didnt use this project idea as i

thought that-

a) It would end up being far too big.

b) It would not be very interesting to construct/examine.

c) It would not be much of a challenge for me.

The idea i finally decided on was

to do a model of the layout of a

septic tank and perculation area as

this would present more of a

challenge for me, would be

interesting to look at and would

aid me in my exam if a scale

drawing happened to come up.

I decided to do this model at a

1:100 scale.

13

Working Drawings and design drawings for artefact-

Plan of septic tank & perculation area aquired from Architecht-

Cutting List-

Baseboard: 297 × 420 (size of an A3 sheet)

Plexiglass-2x 420mm x200mm

-2x650mm x20mm

14

Template-

This will be used to measure

the length & position of the

wires when cutting them to

represent the pipework of the

perculation area.

This will also be used to mark

out the location of the trenches

to be dug for this pipework.

This will also be used for the

location of the septic tank

relevant to the perculation

area.

15

Manufacture of Artefact

Preparation of Materials-

Measuring the base board to the correct size (x)

Measuring the plexiglass to the correct sizes (650x200) x2 and (420x200) x2.

Aquiring of 3 different grades of aggregates -Large→ From my garden.

-Medium→ From my Driveway.

-Small→ From my dads work.

Aquiring sand from my garden.

Aquiring soil from the school grounds.

Marking out-

Used a set square & pencil to mark

out the measurements on the

baseboard.

Used a red whiteboard marker to

mark out the different levels of

aggregates stone/sand/soil.

Marked out the position for the

screws with a gel pen 5mm up from

the bottom of the baseboard and at

equal intervals apart.

Processing of parts-

I pre-drilled holes through the bottom of each of the pieces of plexiglass so as the

screws would fit into them smoothly & tightly.

I then counter sunk each of these holes so as the screws would sit flush with the rest

of the plexiglass & would not be unsightly.

Got the teacher to cut the baseboard on the bandsaw for me so it would be perfect.

16

Assembly-

Step 1

Glued the edges of the baseboard &

got a fellow student to help me.

While he held the plexiglass against

the baseboard one-by-one i drilled

the screws through the pre-drilled

holes in the plexiglass into the

baseboard.

Glued each of the corners of the box

up to the top so the corners would

stay together.

Clamped it so it would dry in place.

Step 2

Placed a block of styrofoam in the

center of the box to-

A) Take up room so i would not

need as much stone.

B) Make my project lighter.

I then filled the bottom of the box

with my first large stone aggregate

up to the first red marking.

17

Step 3

Firstly placed the 2nd layer of

aggregates into the box(small

stones) up to the red line &

ensured it was even all the way

around.

Ontop of this I placed the 3rd

layer of aggregates into the

box(small gravel) up to the next

red line.

Step 5

I then placed the next layer

of aggregates into the box

(sand)

I used a broad flat piece of

wood to scrape across the

top of the sand to ensure it

was flat and even.

18

Step 6

For the final layer of

aggregates i used a shoval to

collect soil from the field

beside my school.

I then distubuted this soil

evenly on the top of the

previous layer of aggregates.

Step 7

Cut up and glued together wiring

to the scale and size of the pipes.

Cut out a template & used it to

dig scale trenches in the correct

location.

Used a kinder egg as a scale

septic tank as it happened to be

the right size, painted it

green and put it in

place.

<-Template

19

Step 8

Cut pieces of wood to scale to the size

of my house. Nailed/glued the pieces

together.

Painted the house grey.

Using a pencil and a ruler drew scale

bricks onto the house.

Using a hammer, tacked felt to the top

of the house and trimmed it with a

stanley knife.

Cut scale batons and super-glued them

onto the top of the roof.

Using a chisel and mallet I cut up a

large piece of slate into scale slates.

I then superglued these slates in place

in 3 rows.

Finishing-

To finish off the project i

made small signs to be placed

around my project to

highlight important sections,

such as the septic tank,

perculation area and the

location of the house.

I also wiped off any of the red

marker that was left on my

project, earlier used to find

the height each of the

aggregates were going to

come to.

20

Modifications-

Took place after step 3

I noticed that the glue i placed on the corners

of the perspex in step 1 was not holding all the

weight in the box together and it was starting

to come apart.

I therefore cut 4 small pieces of wood to fit

into the corners.

I then pre drilled holes in the perspex and

counter-sunk them.

Then I drilled 2 screws into each of these

wooden pieces to tighten the box up.

21

Evaluation of Project

Critical Appraisal of Project

The original plan was good, and if i had

of followed it more strictly my project

may have turned out better.

I should have had more foresight to

recognise in the manufacturing of the

project in step 1 that the glue I placed

on each corner would not be enough to

hold both the perspex box and its

contents in.

The step I took to attempt to rectify the

problem, i see now, was not sufficient

enough to keep the box satisfactorily

together, as each of the walls of the

perspex box began to split and come

apart.

If i was to do the project again, i would

have placed a piece of wood all the way

from the bottom to the top in each

corner, glued and screwed this to the

perspex so it would not come apart.

I now realise that the scale of 1:100 I

manufactured the project to is far too

small and if i was to repeat this project

i would make the scale 25% larger and

increase it to 1:75 so i could put more

detail into the septic tank &

perculation area.

As it is the scale was too small to

include things like-

Gravel around the perculation

pipes.

Detail in the septic

tank(chambers, vents)

The perferations in the perculation pipes.

22

Personal Reflection

I enjoyed working on my project overall and especially enjoyed being able to use my hands

to create something that could be used to aid someone educationally.

I also managed to learn-

How to layout a percualation area and septic tank.

How to use many tools, including- chisel, mallet, hammer, drill and a stanley knife.

How to manage my time and keep to a schedule.

How to use many different substances such as- superglue, woodglue & paint.

I really enjoyed doing the experiments too as i got to see how things worked in a more

practical way and really improved my understanding of aggregates, how they behave and

how they may be used.

Although i enjoyed doing the project and am happy with the end result i dont think that the

amount of effort I put into my project is reflective of the amount of marks being awarded for

it. The fact that the manufacture of the artefact is only worth 8% of the total marks awarded

for construction studies is not really a fair reflection of the work put in.

Completed Artefact

23

Experimental work-To Test DPC

Introduction

In this experiment i will be determining the ability of DPC and

proving that it functions and prevents rising dampness and eventual

damage to a structure. This experiment was carried out between the 22nd of march

& the 23rd of march 2010.

Preparation & Planning

Ensured that i had permission from Mr. Bergin the construction studies teacher to

carry out this experiment in the construction room and leave it there overnight.

Materials Needed-

1 large breeze block.

2 standard bricks.

Equipment Needed-

Basin

Scales

I plan to-

-Place 1 large breeze block into a basin and fill up the basin to cover ¾ of the block.

-Place block A straight ontop of the large block to use as a comparison.

-Place block B ontop of the breeze block with DPC between the surfaces to prevent

contact.

-Weigh the blocks at the start, at 12hours and at 24 hours to compare.

Procedure

1. Place large breeze block into the

basin.

2. Fill the basin until it covers ¾ of the

large breeze block

24

3. Place block A directly ontop of the large

breeze block to use as a comparison

4. Place DPC ontop of the large breeze block

to the right of block A

5. Place block B ontop of the DPC ensuring

that none of the block comes into contact

with either the breeze block or block A.

6. Record the weight of both

blocks after 12 hours and after

24 hours

Health and Safety-

Ensure the test is carried out in a isolated location to prevent tripping or spillage.

Follow all safery rules in the Construction room.

Results

Conclusion & Evaluation Of Results

The results of my experiment showed that block A(without DPC) gained 42grams in weight

in a 24 hour period, while block B actually lost weight-i have determined this was because

the block still retained moisture from being outside & dried out while inside. This proves that

DPC not only works but is essential to all buildings as over time this rising dampness would

severly damage the structural integrity of a building.

Comments

If i was repeating this experiment again i would have allowed the bricks to dry out properly

before carrying out the test and i would have tested a few different materials (wood, cement,

metal) to see which material carries the water fastest.

Origonal Weight After 12 hours After 24 hours Weight change

Block A 2537gms 2569 gms 2579gms +42gms

Block B(DPC) 2894gms 2894gms 2891gms -3gms

After 24-hours

At start

25

Experimental work-Silt Test

Introduction

In this experiment i will be determining the percentage of silt in a sample of sand

using a formula.

Preparation & Planning

Talked to Mr. Black the physics teacher and organised to do the experiment in the physics

lab on the 25th Jan 2010 at 1pm.

Materials Needed-

100ml Water.

50gms of sand.

Equipment Needed-

Graduated cylinder.

Trowel.

I plan to-

Show that over time silt will form ontop of sand

when left to settle. I will also show the

percentage of silt in the sand.

Procedure

1. Fill the graduated cylinder with 50ml of water.

2.Fill the Cylinder until the

level reaches 100ml.

3. Place 50ml of water in cylinder so it

reaches 150ml altogther.

26

4.Shake the Cylinder vigourously and leave to settle.

5.Take measurements after 1hour and 2hours.

Health and Safety-

Ensure the test is carried out in a place where no-one will spill the

contents.

Results

Height of silt layer

Height of sand layer

5

75

Conclusion & Evaluation Of Results

The results of my experiment showed that when left to settle silt does

indeed form ontop of sand. Although the level of silt may be very small it is

significant enough to measure easily enough.

Comments

If i was to do this experiment again i would use a larger graduated cylinder and i would

double the amounts of sand and water so as to get a more accurate result and i would also

record the heights every half hour instead of every hour- this should also ensure a more

accurate result

After 1 hour

X100 = % of silt

After 2 hours

X100 = 6.6 % Silt

27

Experimental Work-The Moisture Content Of Aggregates

Introduction

In this experiment i will be showing the moisture content of aggregates(sand) by

heating it up in a cylinder using a bunsun burner.

Preparation & Planning

I carried out this experiment on the same day as the previous experiment of the 25th

January 2010 at 3pm.

Materials Needed-

1kg of sand

Equipment Needed-

Bunsen burner

Cylinder

Stand

Timer

Weighing scales

I plan to-

Show the moisture content in the sample of sand i have for this

experiment.

Procedure

1. Place 1 kg of sand into the graduated cylinder(it weighs

261g)

2. Heat up the sample of sand and stir it.

3. Measure the weight of the

sand every 30min until the

weight doesnt drop anymore.

After 30 min

28

4.Place results in a table.

Health and Safety-

Ensure safety glasses, overalls and gloves are worn.

Ensure the utmost care is taken when heating the

cylinder.

Ensure gas is switched off at the mains once finished.

Results

Time Weight Change

Start 1261grms

30min 1251 grms 10 grms

60min 1240 grms 11 grms

90min 1225 grms 15 grms

Conclusion & Evaluation Of Results

Wet weight-dry weight

Dry weight

1261-1225

1225

Comments

The test did indeed show the moisture content of the sand but at

a very low level. If i was to do the experiment again i would use

less sand to speed up the process of drying as i think i did not

dry the sand in this experiment quite long enough.

I would also try different types of aggreagates such as soil, gravel and pebbles.

After 1 hour

After 1 ½ hours

X100 = % of moisture content

X100 = 2.9% moisture content

29

Appendix

All the following photos were taken by me or my father-

Pg 6- Trench.

Pg10- The septic tank.

Pg13- The template.

Pg13→19 The manufacturing of my project.

Pg20→25 Photos of my experiments.

Pg26→27 Evaluation photos.

All other images throughout the portfolio are thanks to http://www.google.ie/images