Frequently Ask Question : Septic Tank

29 Jul 2022

1. What is the meaning of “PE” term for Septic Tank?
Population equivalent (PE) or unit per capita loading, or equivalent person (EP), is a parameter for characterizing industrial wastewaters. It essentially compares the polluting potential of an industry (in terms of biodegradable organic matter) with a population (or certain number of people), which would produce the same polluting load.? In other words, it is the number expressing the ratio of the sum of the pollution load produced during 24 hours by industrial facilities and services to the individual pollution load in household sewage produced by one person in the same time. This refers to the amount of oxygen-demanding substances in wastewater which will consume oxygen as it bio-degrades, usually as a result of bacterial activity.To design a network of pipes, pumping stations and sewage processing plants, an estimate should be made on the expected volume flow rate to be carried, pumped and treated. This flow rate is measured in cubic meters per second and should be calculated for existing use as well as for future development. There are various methods for calculating the expected flow rate. One of the methods is to calculate a parameter called "Population Equivalent (PE)" for an area and convert it to a flow rate.
PE is an estimate of the use of sewerage facilities. It's not a measure of population.
For residential areas, the population match is calculated as five (5) for each house and is a direct measure for residents in one area.
However, for commercial areas, PE is calculated based on the floor area, which is commensurate with the number of residents who use the premises. This does not indicate the number of residents living in the area.

The table below shows how PE is calculated.

Type of Establishment Population Equivalent
Residential 5 per house
Commercial :
  Includes offices, shopping complex,
  entertainment / recreational centres,
  restaurants, cafeteria and theatres
3 per 100m2 gross area
School / Educational Institutions :
- Day schools / Institutions
- Fully residential
- Partial residential
0.2 per student
1 per student
0.2 per non-residential student
1 per residential student
Hospitals 4 per bed
Hotel with dining and laundry facilities 4 per room
Factories, excluding process water 0.3 per staff
Market (Wet Type) 3 per stall
Market (Dry Type) 1 per stall
Petrol kiosks / Service stations 15 per toilet
Bus Terminal 4 per bus bay
Taxi Terminal 4 per taxi bay
Mosque / Church / Temple 0.2 per person
Stadium 0.2 per person
Swimming Pool or Sports Complex 0.5 per person
Public Toilet 15 per toilet
Airport 0.2 per passenger/day
0.3 per employee
Laundry 10 per machine
Prison 1 per person
Golf Course 20 per hole

1. Apakah maksud istilah “PE” yang digunakan bagi tangki septik.
Purata Kesetaraan penduduk (PE) atau unit pemuatan per kapita, atau orang yang setara (EP), adalah parameter untuk mencirikan air sisa industri. Ia pada dasarnya membandingkan potensi pencemaran industri (dari segi bahan organik terbiodegradasi) dengan populasi (atau bilangan orang tertentu), yang akan menghasilkan beban pencemar yang sama.? Dalam erti kata lain, ia adalah nombor yang menyatakan nisbah jumlah beban pencemaran yang dihasilkan dalam tempoh 24 jam oleh kemudahan dan perkhidmatan industri kepada beban pencemaran individu dalam kumbahan isi rumah yang dihasilkan oleh satu orang dalam masa yang sama. Ini merujuk kepada jumlah bahan yang menuntut oksigen dalam air sisa yang akan menggunakan oksigen kerana ia merosot bio, biasanya akibat aktiviti bakteria. Untuk merancang rangkaian paip, stesen pam dan loji pemprosesan kumbahan, anggaran harus dibuat pada kadar aliran isipadu yang diharapkan untuk dibawa, dipam dan dirawat. Kadar aliran ini diukur dalam meter padu sesaat dan harus dikira untuk kegunaan sedia ada dan juga untuk pembangunan masa depan. Terdapat pelbagai kaedah untuk mengira kadar aliran yang dijangkakan. Salah satu kaedah adalah untuk mengira parameter yang dipanggil "Population Equivalent (PE)" untuk kawasan dan menukarnya kepada kadar aliran. PE adalah anggaran penggunaan kemudahan pembetungan. Ini bukan ukuran populasi. Bagi kawasan kediaman, padanan penduduk dikira sebagai lima (5) untuk setiap rumah dan merupakan ukuran langsung bagi penduduk di satu kawasan. Walau bagaimanapun, untuk kawasan komersial, PE dikira berdasarkan kawasan lantai, yang sepadan dengan bilangan penduduk yang menggunakan premis tersebut. Ini tidak menunjukkan bilangan penduduk yang tinggal di kawasan itu.

2. How do i determine the suitable model of my propose septic tank?
The method of choosing a suitable or equivalent septic tank according to a development proposal is based on certain criteria. This is to facilitate the stakeholders to determine the appropriate septic tank specifications when drafting the preparation of the ESWAP submission procedure via Indah Water certifying Agency (IWK). Consultancy services on the products, types, models and brands of a specific septic tank can be consulted through the supplier for latest information on the purpose. The selection to determine the septic tank model for a proposal includes the following criteria:

1) Types of development proposals (e.g : Housing, Commercial, Factory and others)
2) Breakdown of calculation Population equivalent (PE) (e.g. 1 x 5PE/House = 5PE)
3) Limitation of space and installation area

2. Bagaimanakah saya menentukan model tangki septik yang sesuai dengan cadangan saya?
Kaedah memilih tangki septik yang sesuai atau setara mengikut cadangan pembangunan adalah berdasarkan kriteria tertentu. Ini adalah untuk memudahkan pihak berkepentingan menentukan spesifikasi tangki septik yang sesuai semasa merangka penyediaan prosedur penyerahan ESWAP melalui Agensi Perakuan Pembetungan (IWK).Khidmat konsultansi berhubung produk, jenis, model dan jenama sesuatu tangki septik boleh dirujuk melalui pihak pembekal bagi mendapatkan informasi terkini bagi tujuan tersebut. Pemilihan bagi menentukan model tangki septik bagi sesuatu cadangan merangkumi kriteria-kriteria yang berikut :
1) Jenis cadangan pembangunan (cth : Perumahan, Komersil, Kilang  dan lain-lain)
2) Pecahan pengiraan purata keserataan penduduk (PE) (cth 1 x 5PE/House = 5PE)
3) Limitasi ruang dan kawasan pemasangan

3.  What is the minimum & maximum effective volume capacity of a septic tank?
Septic tank consists of one unit vertical/horizontal cylindrical tank manufactured in various lengths of configurations to suit design sewage flow rates applicable to a range of population equivalent from minimum of 5 PE up to a maximum of 30 PE. In Malaysia these septic tanks commonly manufactured locally pre-fabricated using Polyethylene (P.E), Fiber reinforced Plastic material (FRP) or Reinforced precast concrete material. These septic tanks are generally in the form of vertically/horizontally-mounted cylinder with minimum effective working volume shall be calculated excluding filter media volume and accumulated sludge volume over 2 years (Desludging and maintenance purposes). This is to ensure the individual septic tank is able to meet the 24 hours hydraulic retention time after 2 years of installation.

The table below shown varies of minimum and maximum effective working volume in litres :

Population equivalent Effective working volume Population Equivalent Effective working volume
5 1525 18 5490
6 1830 19 5795
7 2135 20 6100
8 2440 21 6405
9 2745 22 6710
10 3050 23 7015
11 3355 24 7320
12 3660 25 7625
13 3965 26 7930
14 4270 27 8235
15 4575 28 8540
16 4880 29 8845
17 5185 30 9150

Notes:

  1. Figures extracted from Malaysian Sewerage Industry Guidelines Volume 5, Septic Tanks, 3rd Edition
  2. The Volumetric sizing of tank is based on per capita sewage generation rate of 225 litre per day for a hydraulic retention time of 24 h.
  3. Septic tank is regulated under requirement of Water Services Industry Act 2006 (Act 655)

3. Apakah kapasiti isipadu efektif minimum dan maksimum bagi tangki septik?
Tangki septik terdiri daripada satu unit tangki silinder menegak / mendatar yang dihasilkan dalam pelbagai panjang konfigurasi untuk memenuhi kadar aliran kumbahan reka bentuk yang berlaku untuk pelbagai populasi yang setara dari minimum 5 PE sehingga maksimum 30 PE. Di Malaysia, tangki septik ini biasanya dihasilkan secara tempatan pra-fabrikasi menggunakan Polietilena (P.E), Bahan Plastik Bertetulang Gentian (FRP) atau bahan konkrit pra-tuang bertetulang. Tangki septik ini secara amnya dalam bentuk silinder yang dipasang secara menegak / mendatar dengan jumlah kerja efektif minimum akan dikira tidak termasuk jumlah media penapis dan jumlah enapcemar terkumpul selama 2 tahun (Tujuan nyah enapcemar dan penyelenggaraan).

Ini adalah untuk memastikan tangki septik individu dapat memenuhi masa pengekalan hidraulik 24 jam selepas 2 tahun pemasangan.

4.  How do you get the size and impact of the wastewater treatment plant?
The size of sewage treatment plants has different variations and environmental impacts when compared to small commercial systems with low associated works matrix risk such as septic tanks and small sewage treatment plants (SSTS) according to the scoring scale below:

List of Works Connection Pumping Station Sewage Treatment Plant Small Sewage Treatment System Septic Tanks
Construction 2 3 3 1 1
Alteration 2 3 3 1 1
Disconnection 2 3 3 1 1
Close Up 2 3 3 1 1

Note:

Risk Scoring
(at scale of 1 to 3)

1

Least Risk        : Very low impact, confined and localized harm/Threat

2 Slight risk         : Low Impact, limited spread of harm/threat
3

Moderate Risk : Reasonably impactful, harm/threat extended beyond localize limit.

4. Bagaimana anda mendapatkan saiz dan impak  loji rawatan kumbahan?
Saiz loji rawatan kumbahan mempunyai variasi dan impak persekitaran berlainan jika dibandingkan sistem komersil kecil yang mempunyai risiko matriks yang rendah seperti tangki septik dan loji rawatan kumbahan kecil (SSTS) mengikut pemarkahan skala di atas:

-prepare by Zawahir, Technical Sales last revision June 2022

 


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