Standby Decanter

Introduction
The purpose of Continuous Improvement Project (CIP) is to install temporary floating decanter for SBR plant. There are a few types of decanter were currently equipped at SBR plant. SBR have faced a lot of cases of decanter breakdown especially for arm type decanter. Unlike wastewater pump, installation of decanter at SBR plant never provide standby thus when a unit of decanter breakdown, STP operators have to mitigate the situation in order to keep process sustainability at required level. Failure to have proper action and meeting regulatory compliance will escalate operator into authorities action.

INSTALLATION
The temporary floating decanter will be installed according to depth of decant about 0.8m to 1.2m from top water level. The pump must be provided with a horizontal base baffle plate and attached to the bottom pump cage to minimize direct suction of settle suspended solid inside SBR tank. The temporary decanter outlet pipe must be higher than water level to prevent siphon condition.

Power source of existing decanter will be diverted to the temporary floating decanter, however some modification required especially on the contactor and overload according to power requirement by the pump. The pump should receive operation signal from PLC or main programming in order to replace function as decanter.
 

MODIFICATION

In order installation meets objective, some modification on PLC is required to disable certain interlock such as upper and bottom limit switch of existing decanter. The pump will start when the SBR system has completed the ‘settling’ stage. In some cases, timer counter for SBR programming system is required for the pump to limit its operation just after settling stage and before aeration stage.

Float switch installation may also important to cut off pump operating whenever water at lower pumping level.

What is SBR?

SBR is short term of Sequential Batch Reactor. SBR recognize as one of the economic design of wastewater treatment plant due to land area and structure cost saving. However, decisions should not be based solely on economics but should also include process flexibility, ability to meet permit limits, and long-termviability.

SBR is an activated sludge process. Common of SBR process were illustrated as below:

 

There are 4 main stage completing SBR process for wastewater treatment.

Stage 1:
Filling stage – Wastewater will enter into reactor tank (normally square size) after primary treatment (primary screening, secondary screening, grit and grease removal).

Stage 2:

Reaction stage – The wastewater will be air-injected (aerated) and mixed, purposely to provide oxygen to microbe (endogenous Heterotroph bacteria and protozoan) which decompose organic matter (BOD components) for growth in aerobic conditions. The existence of microbe may observe virtually through brownish water (suspended solid/sludge) during this stage.

In Malaysia, Stage 1 and stage 2 were preceded parallel.

Stage 3:
Settling stage – Filling and reaction (aeration and mixing) no more in place during this stage. The condition allows stagnant water whereas suspended solid will settle bottom inside the reactor. Two obvious liquid layer existed which top is clear treated water and bottom is sludge. By completely assuming here, more compacted sludge is flocculated and ready for return or waste.

Stage 4:

Decanting stage – Removing clear treated water (effluent).

RIVER OF LIFE

Malaysia currently undergoes significant transformation of reservation of water sources by river cleaning, beautification before year 2020. It is put Listed under Greater KL project to increase high economic value.

Greater KL project include transformation of sewerage treatment line and facility, to enhance operation and services.

NOT many would believe that there is an impending water shortage in Malaysia, especially if they are Kuala Lumpur folks who are often caught in traffic jams caused by downpours. But if climate change alters the favorable rainfall pattern, we will have to come to terms with water rationing or other drastic water conservation measures. - according to THESTAR

Rivers have long been recognized as one of humanity’s most important natural resources. They are one of the most important of all the natural resources necessary to ensure human health and civilization. A close association between cities and water is inherent over the history of civilization and in fact, many urban cities in Malaysia are located close to river areas. The last two decades have shown Malaysia has shifted development strategy from an agricultural base to industrialization, and manufacturing industries have now become the main component of the economy for the country. This transformation since the 18th century has clearly shown that rapid urbanization, industrial and intensive agricultural activities, as well as wide-spread land development, have contributed to extensive changing of river functions for the economy, national development and the environment. In particular, river roles have become less significant for human life and river functions limited to transportation purposes only.

Environmental Management System (EMS)

What is EMS?

An environmental management system is the process used by an organization to manage, review, correct, and improve the organization’s approach to business. Employees are asked to consider how they affect the environment every day.  An EMS offers a structured way to incorporate environmental considerations into day-to-day operations; it promotes continual improvement of the environment and human health.

EMS key all about

1. Systematic way of managing an organization's environmental affairs

2. Based on Plan-Do-Check-Act (PDCA) cycle. Some EMS approach being made Policy-Planning-Implementation- Checking corrective action- Management review.

3. Focussed on continual improvement of system

4. Addresses short term and long term impact of a product or services provided by the company to environment

5. A tool/method to improvement environmental's performances

Conducting EMS in an organization require commitment from all department. Some senior management likely stepping back to commitment because EMS depending on voluntary approach.

Conducting EMS in an organization will reduce waste, increase process effieciency, increase environment safety, eliminate insurans claims, provide uniform operations, increase productivity and saving operation cost.

What is Hydraulic Retention Time

The Hydraulic retention time (HRT) also known as Hydraulic residence time or t (tau), is a measure of the average length of time that a compound remains in a constructed reactor.

Hyraulic retention time is the volume of the aeration tank divided by the influent flowrate:

HRT represent differently according to type of bioreactor. HRT is usually expressed in hours (or sometimes days).

Phosphorus Removal in Activated Sludge Process (by PAOs)

In Anaerobic Treatment Tank

1. Polyphosphate accumulating organisms (PAOs) decompose polyphosphate (PP) and produce orthophosphoric acid (called orthophosphates)

2. By decomposing, PAOs gain energy and assimilate organic substances (volatile fatty acid, acetate). It is accumulated in PAOs body as polyhydroxoalkanoate (PHA) (called polyhydroxybutyrate, PHB)

In Aerobic Treatment Tank

3. PAOs decompose PHA which earlier stored in their body

4. By decomposing, PAOs gain energy (live and grow) and uptake orthophosphoric acid and accumulate in PAOs body as PP

5. Phosphorus element being discard from system through wasting (WAS) PAOs from final sedimentation tank.

Preparation of Dewatering Polymer

Procedure 1: Preparation of dewatering polymer (0.1%)


1. Fill polymer mixing tank with tap water (500L, 1000L, or 1500L).

2. Weight dry powder polymer (0.5kg, 1.0kg or 1.5kg)

3. Start polymer mixer and run continuously.

4. Pour the weighted dry polymer slowly into moving water. Be careful during pouring to prevent bulk powder entering the water and dust from flying over.

5. Mix the solution (dry powder polymer + water) 45 minutes to 1 hour until homogenous solution achieved (no powder/particle suspended in the solution).

Working Flow of Energy Saving at Sewage Treatment Plant

 

Characteristic of Protozoa in Activated Sludge Process

Group 1, 2 and 3 : Characterize of young sludge inside activated sludge process

The protozoa consist of  predominate Amoebae and flagellates with a few free swimming ciliates.

Group 4:  Characterize of mature sludge inside activated sludge process

For municipal wastewater treatment plants the most desirable stage of the ecological succession is the stage where both stalked ciliates and free swimming ciliates are observed with possibly a few rotifers. This stage is is correlated with rapid settling of solids and easy separation of solids from water. The resulting effluent is correspondingly low in turbidity, suspended solids and biochemical oxygen demand (BOD).

Group 5: Characterize of old sludge

Predominating of rotifers and nematodes with fewer stalked ciliates.

Examples of group 4 protozoa: Vorticella and Epistylis

Floating Scum Skimmer

Material to construct floating skimmer ? Water engineers are likely focussing on studying density values of PE polymers .

UHMWPE is polyethylene with a molecular weight numbering in the millions, usually between 3.1 and 5.67 million. The high molecular weight makes it a very tough material, but results in less efficient packing of the chains into the crystal structure as evidenced by densities of less than high density polyethylene (for example, 0.930–0.935 g/cm3). UHMWPE can be made through any catalyst technology, although Ziegler catalysts are most common. Because of its outstanding toughness and its cut, wear and excellent chemical resistance, UHMWPE is used in a diverse range of applications. These include can and bottle handling machine parts, moving parts on weaving machines, bearings, gears, artificial joints, edge protection on ice rinks and butchers' chopping boards. It competes with Aramid in bulletproof vests, under the tradenames Spectra and Dyneema, and is commonly used for the construction of articular portions of implants used for hip and knee replacements.

HDPE is defined by a density of greater or equal to 0.941 g/cm3. HDPE has a low degree of branching and thus stronger intermolecular forces and tensile strength. HDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts or metallocene catalysts. The lack of branching is ensured by an appropriate choice of catalyst (for example, chromium catalysts or Ziegler-Natta catalysts) and reaction conditions. HDPE is used in products and packaging such as milk jugs, detergent bottles, margarine tubs, garbage containers and water pipes.

PEX is a medium- to high-density polyethylene containing cross-link bonds introduced into the polymer structure, changing the thermoplast into an elastomer. The high-temperature properties of the polymer are improved, its flow is reduced and its chemical resistance is enhanced. PEX is used in some potable-water plumbing systems because tubes made of the material can be expanded to fit over a metal nipple and it will slowly return to its original shape, forming a permanent, water-tight, connection.

MDPE is defined by a density range of 0.926–0.940 g/cm3. MDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts or metallocene catalysts. MDPE has good shock and drop resistance properties. It also is less notch sensitive than HDPE, stress cracking resistance is better than HDPE. MDPE is typically used in gas pipes and fittings, sacks, shrink film, packaging film, carrier bags and screw closures.

LLDPE is defined by a density range of 0.915–0.925 g/cm3. LLDPE is a substantially linear polymer with significant numbers of short branches, commonly made by copolymerization of ethylene with short-chain alpha-olefins (for example, 1-butene, 1-hexene and 1-octene). LLDPE has higher tensile strength than LDPE, it exhibits higher impact and puncture resistance than LDPE. Lower thickness (gauge) films can be blown, compared with LDPE, with better environmental stress cracking resistance but is not as easy to process. LLDPE is used in packaging, particularly film for bags and sheets. Lower thickness may be used compared to LDPE. Cable covering, toys, lids, buckets, containers and pipe. While other applications are available, LLDPE is used predominantly in film applications due to its toughness, flexibility and relative transparency.

LDPE is defined by a density range of 0.910–0.940 g/cm3. LDPE has a high degree of short and long chain branching, which means that the chains do not pack into the crystal structure as well. It has, therefore, less strong intermolecular forces as the instantaneous-dipole induced-dipole attraction is less. This results in a lower tensile strength and increased ductility. LDPE is created by free radical polymerization. The high degree of branching with long chains gives molten LDPE unique and desirable flow properties. LDPE is used for both rigid containers and plastic film applications such as plastic bags and film wrap.

VLDPE is defined by a density range of 0.880–0.915 g/cm3. VLDPE is a substantially linear polymer with high levels of short-chain branches, commonly made by copolymerization of ethylene with short-chain alpha-olefins (for example, 1-butene, 1-hexene and 1-octene). VLDPE is most commonly produced using metallocene catalysts due to the greater co-monomer incorporation exhibited by these catalysts. VLDPEs are used for hose and tubing, ice and frozen food bags, food packaging and stretch wrap as well as impact modifiers when blended with other polymers.

Recently much research activity has focused on the nature and distribution of long chain branches in polyethylene. In HDPE a relatively small number of these branches, perhaps 1 in 100 or 1,000 branches per backbone carbon, can significantly affect the rheological properties of the polymer.

Water which is denser than HPDE , will cause HPDE to float on water surface , thus floating scum will be collected to floating skimmer system.