An Overview on Major Design Constraints, Impact and Challenges for a Conventional Wastewater Treatment Design

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 7-16

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal web link: http://www.jett.dormaj.com

https://doi.org/10.47277/JETT/9(1)16

An Overview on Major Design Constraints, Impact

and Challenges for a Conventional Wastewater

Treatment Design

Saidur R Chowdhury *, Feras Alhelal , Mohammad Alahmadi , Naif Alqahtani , Abdullah

Alkhaldi , Andi Asiz

Assistant Professor, Civil Engineering Department, Prince Mohammad Bin Fahd University (PMU), Al khobar, Saudi Arabia

Saudi Consolidated Engineering Company, Khatibalami, Khobar, King Faisal Road. KSA

Civil Engineering Department, Prince Mohammad Bin Fahd University (PMU), Al khobar, Saudi Arabia

Received: 08/07/2020

Accepted: 04/09/2020

Published: 20/12/2020

Abstract

The conventional wastewater (WW) treatment plant includes physical, chemical, and biological treatment processes that can protect the

receiving water bodies from water pollution. The common design constraints, challenges as well as environmental impact would make the

wastewater treatment plant’s (WWTP) construction and operation more complex and demanding tasks. Major project constraints for WW

plant design are economics, accessibility, fulfilling technical requirements, institutional set-up, health and environment, personnel capacity,

and political commitment etc. Design methodology adopted in the current study included project location, unit selections, the design capacity,

design period as well as proximity to the population and layout plan. The present manuscript discussed briefly about effluent quality

requirements, design issues, environmental impacts, details, and safety concerns. It also highlighted the necessary flexibility to carry out the

treatment satisfactorily within the desired range of influent WW characteristics and flows. In the present study, every step of the design was

verified with Environmental Regulations and suggested to overcome all constraints while designing WWTPs so that standard operational

code for the specific region could be implemented to achieve the best treatment performance. The results obtained from analytical calculation

were optimized to achieve the best design parameters for field application. The optimized values also reduce the construction and operation

cost during the field application.

Keywords: Wastewater (WW), Challenges, Constraints, Design, Impact, Treatment, Plant

depending on the resources’ availabilities (7). The conventional

Introduction

steps include primary, secondary to tertiary treatment (1). Primary

treatment considers as the first step of WW treatment. Many

advanced WWTPs located in the developed countries started with

primary treatment and then equipped with other treatment units as

increasing wastewater loads and the requirement to produce clean

water prior to final disposal into receiving bodies (7). The

treatment also increases the production of treated water for

agriculture and other developments. Primary treatment is used to

reduce suspended and floating solids from raw WW. This level

can be defined as mechanical or physical treatment, although

chemicals are often applied to complete the sedimentation process

Wastewater (WW) treatment plant is very important as any

other necessary facility for constructing a sustainable city.

Domestic wastewater treatment consists of various units to

remove different types of contaminants from WW (1-3). It

includes physical, chemical, and biological treatment processes

that can protect the receiving water bodies from water pollution,

make recycled water as well as reduce the volume of sewage

water and sludge (4). Environmental benefits from WW include

safer and more stable healthy aquatic ecosystems and reduce

amount of wastewater released into the environment without any

treatment (5). Any wastewater treatment provides an opportunity

for sustainable solution to some aspects of the water scarcity

problem (6). The proper management of wastewater develops the

sustainable and healthy environment (5). The common design

constraints, challenges as well as environmental impact would

make the WW treatment plant’s construction and operation more

complex and demanding tasks. WW treatment contains a series of

steps that can have increasing effectiveness and complexity

(

8). Primary treatment can reduce the biochemical oxygen

demand (BOD ) and chemical oxygen demand (COD) of the

incoming wastewater by 25-50% (8-9). During primary treatment,

the total suspended solids are removed by approximately 50-70%

as well as 65% removal could be achieved for oil and grease (9).

Secondary to tertiary treatment applies to purify wastewater more

and can also act as a resource recovery unit (7).

Corresponding author: Saidur R Chowdhury, Civil Engineering Department, Prince Mohammad Bin Fahd University (PMU), Al-khobar,

Saudi Arabia. E-mail: schowdhury1@pmu.edu.sa

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 7-16

The production and maintenance cost of treated water exceeds

that of potable water in many regions of the world where sources

of fresh water supply are plentiful. However, introduction to

innovative technology in the water industry, the reclaimed water

is usually sold to citizen at a cheaper rate to encourage it’s use (7).

Ouda (7) further reported that fresh water supplies to the

community would be inadequate due to increased population

demands, or unplanned urbanization, and reducing clean water

sources. In addition, using reclaimed water for non-potable uses

save potable water for drinking, since less potable water is used

for non-potable uses such as irrigation. Every human being uses

the water in different way such as domestic, agriculture, and

industrial or even for drinking. In the present study, design

constraints, environmental impacts, costs and few challenges

were highlighted to develop any conventional treatment plant in

any newly developed cities. The outcome of the present study was

extracted from the student capstone project in the civil

engineering department at Prince Mohammad bin Fahd

University (PMU) in Saudi Arabia. The study explored the

processes to complete any conceptual treatment design within

limited resources. In the present study, a large area in Al Firdous

District under Jubail Industrial City in Eastern Province was

selected to develop a sustainable new housing district. This new

district includes houses, commercial complexes, multi-storey

building, and gas stations. It is expected that in addition to the

current volume of wastewater, a significant amount of wastewater

would be generated from the area in the near future. If this

wastewater would be discharged into the environment without

treatment, it could be a severe threat to the public health and

hazard to the environment. Thus, the proposed wastewater

treatment plant within the new districts can help to reduce the

pressure on the existing wastewater treatment plant (WWTP) in

Jubail Industrial City in Kingdom of Saudi Arabia (KSA).

The present study aimed to design a wastewater treatment

plant to serve the community. The scope and objectives of the

study were to evaluate major design constraints, impact and

challenges while designing any conventional WW treatment

plants. The manuscript also included the required consideration

for plant construction site, the degree of effluent quality, design

issues and details, outfalls, important facilities and common

safety issues. The study also calculated volume of WW to be

generated during the design period of 25 years; to develop the

conceptualized design for the primary and secondary wastewater

treatment units (based on the estimated wastewater); to assess the

environmental impact of the proposed wastewater plant. The

present study also verified major design requirement and

consideration for successful WW plant operations. Till to date,

very few studies have investigated constraints, impact and

challenges for a conventional WW treatment plant design. This

was one of the studies that focused on the basic information

necessary to overcome the design constraint, sustainability and

key challenges for constructing conventional WW treatment plant

within newly developed cities under different environmental

conditions.

WW, applying standard practices for the necessary design

parameters and optimizing design parameters based on applicable

constraints and regulations. A proposed WWTP project intended

to be located in Al Firdous District of Jubail Industrial City was

used as the main vehicle for analyzing and synthesizing design

information, process, and optimization. In the study, all analytical

calculations for different design parameters were optimized by

MS Excel Solver for verification and Justification.

Environmental Impact Assessment (EIA) was evaluated by

field visits and document study. The results of EIA for the

proposed project were verified and contrasted with the recent

design practices. Important information about the project site and

existing environmental condition was discussed with the Local

City Corporation and stakeholder to ensure its feasibility. All

observations and design constraints were identified, compared,

verified as well as provided justification for solution by the

investigators. Design steps were evaluated based on applicable

theories, expert opinion, site condition, and optimum standard

values. At the end, all potential challenges were summarized in

this study and their possible solutions were discussed. The

manuscripts also listed some important considerations to

successfully complete any WWTP design that could fit with site

condition for a newly developed plant.

WW Project Constraints and operational code

Sustainable development provides a good standard of living

in any society. It can facilitate important solutions to the financial,

environmental, and societal challenges without causing a hazard

to human and environmental issues. Environmental protection

and conservation of natural water body consider design

requirement and design consideration significantly while any

sustainable development in environmental sector takes place.

Water pollution from wastewater discharges may vary depending

on their types, sources and strength. These wastewaters entered

into the natural water body through various channel can cause a

great concern to community. The conventional WW treatment can

reduce this problem. Prior to constructing WW plant, numerous

constraints need to be checked for sustainability. Any design

constraint for WW project means the list of problems that are

counted to overcome prior to the final design approval in case of

successful construction and plant operation. Major project

constraints for wastewater plant design (WWTP) are economics,

accessibility, health and environment, prevailing wind direction,

suitability of hydrogeological condition, fulfilling technical

facilities, institutional set-up and personnel capacity and

policy/political commitment etc.

Another major constraint for wastewater treatment plant is

enforcement of standards’ monitoring. The design capacity for

wastewater plant should be such that the treated effluent would

continuously meet accepted quality criteria that can reduce any

risk. WWT related risk occurs due to the failure to meet

established standards at source (i.e. WW treatment outflow); not

complying standard operation procedure (SOPs); lack of qualified

employees to monitor treatment facilities; ineffective monitoring

of WW reuse system; absence of skilled personnel; lack of proper

monitoring equipment; and expensive operation and monitoring

costs (Ministry of the Environment 2008) (10).

Study Methodology

The methodology used in the study included: by reviewing

and verifying literatures on WWTP design, recent site related

WW document studies, site history, evaluating feasibility of site

condition through field visits, verification of existing sources of

An area selected for treatment plant also requires some

important consideration such as distance from wastewater source

and final discharge point for treated effluent, landscape as well as

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 7-16

neighbourhood community. Local temperature, rain, humidity as

well as climate also affect different treatment unit performance.

For example, bacterial growth in aeration tank during high

temperature as well as excess flows due to rainwater could affect

the processes and removal capacity. Readily available materials

and chemicals should be considered during the plant’s

construction and operation. These constraints could affect the

project cost. Lack of sufficient skilled personnel also affects the

equipment handling during plant operation. Those common

constraints should be checked prior to finalize the treatment plant

projects. After constraint study, another important factor such as

operation/design code followed by environmental rules and

regulation in any country should be verified. In the present study,

every step of the design was verified with Royal Commission

Environmental Regulations (2004) as well as Presidency of

Meteorology and Environment Regulations and rules in KSA

order to carry out the EIA of proposed wastewater treatment plant,

baseline study was conducted for project location,

neighbourhood or site surrounding environmental study,

population growth, climate, effluent discharge, operational, and

ecology. Parameters of importance can be defined from this EIA

study as well as standards for discharge can be selected to

establish permissible limits of contaminants in WW effluents

being treated at the plant (14). Appropriate mitigation measures

were evaluated and recommended to be incorporated into the

intended plant. Table 1 represents the primary list of items to be

verified for the purpose of environmental impact assessment prior

to plant design. An example was provided in Table 1 that showed

important items of preliminary EIA study for Al- Firdous District

WWTP under Jubail Industrial City in Eastern Province in KSA

(prior to WWTP design). The status of important environmental

parameters (for the development of treatment plant) at the

proposed site was checked and verified.

(

2001) (11-12). The conceptualized discharge water quality was

established as per performance standards for discharge according

to KSA environmental regulation. Figure 1 shows the major

constraints for a wastewater treatment plant design. All

constraints should be overcome so that standard operational code

for the specific region can be implemented to achieve the best

treatment performance.

In the first stage of EIA, the historical documents about

neighbourhood, their life style and standard, site information, any

accidental spillage or event as well as population growth etc. were

checked for the proposed location. Prior to finalizing the design,

different environmental parameters such as prevailing wind

direction, land, location and accessibility of the plant site, hydro-

geologic condition, soil and topography, discharged point, as well

as sludge management were checked and compared with Saudi

Environmental Regulation standards (2001) (12). The second

portion of the study was field investigation (FI). If the result from

portion one study fails to fulfil the requirement as per standard,

FI would be deemed necessary to confirm the findings obtained

from the portion one study. FI generally includes soil,

groundwater collection and field or laboratory investigation as

well as hydrogeological parameters’ identification, such as wells

or groundwater flow.

Important Steps for WWTP design

Design methodology adopted in the current study included

project location, unit selections, capacity, the design capacity,

design period, environmental assessment (e.g. wind direction) as

well as proximity to the population and layout plan.

Figure 1: The flow chart of major constraints for a WW treatment plant

design

5.1 Location of treatment plant

A new WW treatment plant site or an expansion of an existing

Environmental Impact Assessment (EIA) and

WW treatment plant must be evaluated by the Professional

Engineers (Ministry of the Environment 2008) (10). The

treatment plant should be situated close to the point of disposal.

An important care should be considered while selecting the site.

The plant site should be located on the downstream portion of the

city and also sufficiently away from water intake works, drinking

water sources, and groundwater wells. If the final disposal of

treated effluent would be on natural water bodies or abandoned

ponds/low land, the plant must be located near to the disposal

point so that the site can receive the treated sewage directly under

gravitational forces. The plant site should not be far away from

the town so that the length of the sewer line could be less.

WW Project

EIA study is an essential part for any sustainable WW project

implementation. It can help to decide the best project location for

the construction of treatment plants and also protect individuals,

society and environment from any bad effect due to the

construction of WW treatment plant. The investigation also

identifies adequate safety measures to be introduced to ensure

public safety and local environment, which might arise due to any

emergency or unexpected situation (13). They reported that it

would also evaluate the proper monitoring and operational

condition to be required for wastewater treatment plant.

In the present study, EIA was divided into two portions. First

portion was documents or historical information review and

second portion included site visit and field investigation (FI). In

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 7-16

Table 1: Selected items to be verified for the preliminary environmental impact assessment (EIA) prior to the design (an example for Al-

Firdous District WWTP under Jubail Industrial City in Eastern Province in KSA)

Not checked/

not satisfied

Selected items for EIA

Satisfied

Remarks/Comments

Historical document studies around the

project site

√

Checked previous land uses, living standards, population etc.

The subject site is vacant and plain land. Enough space available for

future expansion and sludge disposal/utilization close to the site

Nothing (e.g. natural significance area, parks or institute) observed

within 250 m of the proposed location. The study protects human, all

living being and their surrounding such as air and soil from

environmental hazards.

Proposed land area for WWTP facilities

Neighborhood or site surrounding

environment study for project site

evaluation

√

Wastewater or toxic substances could be collected (within the plant

capacity) without deleterious effects and without destruction to aquatic

environment or humans who consume/use the water.

Capacity of the treatment plant to be

handled

√

WW sources and physical condition (e.g.

temperature, flow, size, types of waste

Sources as well as quantity of wastewater checked

etc.)

Location and accessibility of the project

site

Population Centers

from project site

Prevailing wind direction of the project

site

√

Easily accessible to the plant. Few kilometers from the WW sources.

Population centers are an advantage for WWTPs from the point of

view of ease of supply planning.

Odor (generation from wastewater plant) towards the sea

Shrubs need to be cleared at the project location during the excavation

work

No wells on or near the site. Groundwater depth approximately 2 m

below the grade. Cautious required to prevent GW contamination

Sludge collected from plant to be used for different engineering

purposes

Soil and topography of the project site

Hydro-geologic condition of the project

site

Waste management and constraints of the

project site

Soil types or condition for any facility

development in proposed WWTP

√

Mostly sand

Ambient air parameter of the project site

Soil and groundwater testing

Discharged point

Not checked

All laboratory investigations were conducted by third party. No toxic

substance detected.

√

Final disposal towards Sea

Checked with KSA

Environmental Regulation

Performance standards for discharge

Notation: √ = Checked and Satisfied

On the other hand, the plant site should not be too close to the

city, that it can create problems in the expansion of city and can

contaminate the neighbourhood or general atmosphere by smell,

fly and nuisance (15-17). The building orientation and location

can be utilized to reduce the effects of odours. Susceptibility of

site to flooding, soil conditions, and suitability of subject site with

respect to access to receiving body of water should be investigated

by Professional Engineers prior to finalizing the WWTPs location

developments, feasibility for addition or expansion, financial

constraints and interest rate (1, 18-19)

The treatment plant is commonly designed and constructed

that can meet the demand for plant operation over 20 to 25 years’

period (8, 10). The time lag between the design and completion

of plant construction should not be more than 2-3 years. A WWTP

also involves installing of underground sewer pipes that can carry

all WW as well as construction of costly treatment units. The units

which cannot be replaced or increased in their capacities easily or

conveniently at a later date should be considered always while

designing any plant. The future expansions of the city and

consequent growth in the WW quantity should be forecasted

(within design period) in order to avoid such complications. All

units can serve the community satisfactorily for a reasonable year.

A care should be considered that the plant should not be under

loaded in the initial stages, particularly the sedimentation tank.

The design engineer should set the ultimate design period to be

(

Ministry of the Environment. 2008) (10). In the selected location

of WWTPs, the design engineers should consider a plant layout

where the different processing units would be constructed or

arranged in a logical progression. The plant layouts are facilitated

to offer for convenience of operation and ease of flow splitting for

different treatment units. In addition, the selected site has enough

space to accommodate future plant expansion so that any

additional processes can be installed to recover the treatment

quality.

20 to 25 years and to that extent sufficient accommodation should

be accommodated for all the units necessary to fulfil the need of

forecasted population.

.2 Design period

The design period should be chosen based on useful life, wear

and tear, expected population growth and infrastructural

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 7-16

design consideration for WWTP project.

.3 Layout Plan

Proper wastewater layout plan must be completed before

design flow establishes. A site for WWTP would be considered

on the basis of evaluation of the entire drainage area, the

topographic map, subsurface conditions and natural grades that

could facilitate the necessary services at a minimum cost

6 Degree of Treatment and Basic Design

The degree of treatment would be based on the influent

characteristic and the required effluent quality. Final sludge

disposal options or resource recovery options can dictate the

choice of treatment processes as well as the effluent quality. The

available land area, soil or geo-hydrological conditions, treated

WW during periods of the year (where receiving streams

experience insufficient flows) and downstream recreational water

uses also have direct indirect influences in case of the treatment

method selection (Ministry of the Environment, 2008) (10). The

technical supports such as operator skills, mechanical

performance, future loads such as hauled septage as well as

leachate handling, operation and maintenance (O&M) costs are

one of the considerations to select the degree of treatment. Before

deciding upon the WW treatment processes, the designer should

assess the alternative options available to conduct the required

level of treatment (in terms of treatment capability, overall capital

and operational costs). If the effluent is discharged into the natural

water, it should comply with the national discharge quality

requirements. If treated water used for land irrigation, the plant

effluent must also satisfy the health regulation governing the

types of crops that are irrigated. The treated effluent can be used

for recreational lakes, agriculture, industrial and municipal

purposes. Thus, requirement for WW discharge based on uses

may dictate the effluent quality and the degree of treatment (18).

Figure 3 shows the conventional domestic wastewater treatment

units for the conventional project.

(

Ministry of the Environment, 2008) (10). The preliminary layout

of wastewater is most commonly prepared from the topographic

map (18). In general, wastewater sewers are located on streets or

on available right of way and are sloped in the same direction as

the slope of the natural ground surface. Preliminary layout and

routing of wastewater flow can be done by considering several

feasible alternatives. In each alternative, factors (such as total

length of wastewater treatment, cost of construction, operation

and maintenance) also consider to build a cost effective

wastewater system. Finally, these flow channel layout plans are

revised after several field visits and investigation to the location.

On the other hand, all building structures proposed in the layout

of the plant should facilitate adequate allowances for the future

linear expansions of the various treatment stages and process for

different unit. The designer orients the plant so that the best

advantage can be provided from the prevailing wind and climate

conditions. The building orientation can be set to decrease effects

of odours, energy usage (heating) and other operational problems.

To avoid the necessity for major pipelines or conduits to convey

WW, sludges from one units to other, the various processing units

are set in a logical progression so that the arrangement of plant

layout can provide for convenience of operation and ease of flow

splitting for proposed and future treatment units. Moreover,

designer should keep some space for the provision of future

treatment plant expansions if necessary. Figure 2 shows the major

Figure 2: The major design consideration for WWTP project

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 7-16

Figure 3: The proposed domestic wastewater treatment units

The conventional WWTP design would focus on the maximum

removal of Biochemical Oxygen Demand (BOD), Total Solid

The notations of all parameters for activated sludge tank were

included in Column 2 under the Table 2. All important equations

used for calculating design parameters were presented in the,

Table 2 Column 1. At the beginning, the predicted populations

were calculated using the basic growth equation. Then, receiving

water chamber was designed. This tank structure at the entrance

of the treatment plant to receive the wastewater approaching

through a wastewater system and main pipe would be connected

to the first unit tank. Three Bar screens such as two mechanicals

with 90 degrees and one manual with 45 degrees were proposed

to trap and remove the floating materials such as cans, papers, tree

leaves, timber pieces etc. In the design, grit chamber would be

proposed to be placed after the screening to remove the inorganic

particles. A settling tank called primary sedimentation tank was

designed to remove the organic solids. In this study, aeration tank

was designed for secondary treatment facilities. The amount of

activated sludge from secondary sedimentation tank was

calculated and to be used for the aeration tank. Table 2 shows all

important equations used to calculate the design parameters for

the aeration tank design. The overall successful design could be

achieved by accomplishing environmental system design,

hydraulic flow design as well as physical and structural design of

the plants (20).

(

TS) and Suspended Solids (SS), Settleable Solids, Total Kjeldahl

nitrogen (TKN) and Total Phosphorus (TP). In the present study,

the treatment plant was proposed to treat domestic or municipal

WW. WW would require the primary treatment to remove large

objects, grits and sludge (as shown in Fig 3). Then, the WW

would be conveyed to the secondary WWTPs for further

treatment. The medium strength of wastewater was considered as

influent wastewater for different treatment units while designing

the WWTP project.

The study assessed the performance of suspended solid aerobic

treatment unit for municipal wastewater generated from almost

3000 population in Al Jubail residential area. The design also

considered assessing the site condition, biomass calculation, Food

and micro-organism (F/M) ratio, amount of recycled activated

sludge, TSS, VSS, COD, BOD removal efficiency as well as

physical and process design of the proposed wastewater. The

study also evaluated important design parameters (e.g.

environmental and Hydraulic) for screening, grit removal,

primary/secondary treatment units and also verified with Royal

Commission Environmental Regulations as well as Presidency of

Meteorology and Environment Regulations and rules in KSA.

Table 2 listed few basic equations necessary for activated sludge

tank design proposed in the study.

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 7-16

Table 2: Few basic equations necessary for activated sludge tank design (8)

Equations

Parameters

Descriptions

Q= Maximum WW flow rate; P= future population;

Q’= Wastewater produced (Liter per capita)

Estimation of maximum

designed flow rate

Q = P *Q’/1000

푉

휃 =

푄

휃= hydraulic retention time (days);

V= aerated tank volume, V (m )

From flow rate

Y = Yield coefficient or bacteria growth rate; 휃푐 =

sludge age, days ; So = Concentration of dissolved

pollutants such as BOD, mg/L; S= Concentration of

dissolved pollutant in aerated tank and the effluent,

푌푄휃푐 (푆표 − 푆)

Estimation of aerated tank

volume, V (m )

푉 =

푋 (1 + 퐾푑휃푐)

mg/L; k = Decay rate of the bacteria; X = The

mixed liquor suspended solid concentration MLSS

= Waste sludge flow rate m /day; X

푌푋

휃푐 =

Concentration of recycled activated sludge; X

Effluent suspended solid concentration, mg/L;

Estimation of sludge age

푄푤푋푟 + (푄 − 푄푤)푋푒

푋

푄푟 = 푄

Qr = Return sludge flow rate, m /day;

푋푟 − 푋

F = Food ( e.g. amount of COD or BOD

concentration, mg/L); M = Micro-organisms ( e.g.

concentration of VSS, mg/L)

Food and micro-

organisms ratio for

optimum operation

퐹

푄푆표

푀

푉푋

푑푥

푑푡

푉푋

휃푐

The rate of sludge

production

dx = the change of VSS; dt = the change of time

Total substrate

U = Substrate utilization rate (e.g. food consumption

by micro-organisms); Ks = half velocity constants;

μm SX

consumption calculated

by multiplying tank (v)

U =

Y (KsꢀS)

-1

휇 = maximum growth rate constant, d

volume, m .

results were optimized to achieve the best design parameters for

field application. The optimized results also reduce the

construction and operation cost as well as overcome all design

constraints identified prior to the design approval. The optimized

parameters fit well with filed application and save construction

time.

Design Optimization

After the analytical calculation, the calculated values need to

be justified or optimized so that the accuracy of the design

parameters would be fitted well with the environmental processes

as well as construction operation during the field application.

Design constraints also control the parameter selection. In this

project, MS excel solver was used to solve and optimize the

design parameters. The solver results act as criteria or standard.

Solver can work with a group of compartments, called decision

variables or simply variable cells that are used in computing the

formulas in the certain scope and constraint cells. It can adjust the

values in the decision variable cells to fulfill the limits on

constraint cells and calculate the results the design engineer wants

for the objective cell.

In this project, some parameters used were constant and some

were variable while operating the excel solver to evaluate the

targeted parameters. The solver optimized the results within the

range. Those calculations were based on the width, depth, area,

slope, friction with slope and flow rate. Table 3 shows an example

of design of Bar Screen and the channel flow using analytical and

solver solutions that was used while designing Al Firdous District

WWTP under Jubail Industrial City in Eastern Province in KSA.

Similarly, all other parameters calculated by analytical methods

for other units (e.g. sedimentation tanks, aeration tank, filtration

or coagulation) were verified with the solver results so that the

8 A Conventional Challenges in WW plant

The common challenge in WW industry is to remove

contaminants as per requirement so that the desire goals can be

achieved. The application of treated WW can control the

treatment mechanisms as well as the effluent quality. For

example, WW usage in agricultural activities should be always

treated at the level that always conforms the standard limit set for

agricultural water quality. If treated water is discharged into

natural water bodies, the level of treatment should be able to

control any detrimental effect generated from the disposal in

aquatic environment. Thus, the primary challenge in WW

industry is to maintain the quality of WW. The selected treatment

needs to meet with current regulatory standards as well as reduce

the environmental impact on the receiving water body (21).

Another challenge in the WW treatment project is construction

and operating costs. It should be optimized. Cost estimation for

wastewater treatment plant is one of the major tasks in any

project.

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 7-16

Table 3: Design of Bar Screen and the channel flow using analytical and solver solutions (for Al- Firdous District WWTP under Jubail

Industrial City in Eastern Province in KSA)

Optimum

Input data

Solver

Hand calculation

Values

(Davis, 2011)

Coefficient of roughness ( n)

0.012

0.456

0.0001

0.012

0.456

0.0001

Discharge, Q (m /s)

Slope of energy grade line, S (m/m)

Width, m

Depth, m

Calculated velocity

Adjusted Area (m²)

Perimeter, m

A =

1.04

2.89

0.36

0.506

0.01

0.43

0.45

P =

Hydraulic radius, m

R =

0.33

0.478

0.01

0.39

R^2/3 =

S^0.5 =

Velocity of channel flow, m/s

Adjusted flow rate, (m /s)

Cross sectional area of flow, m²

Q/v=

1.04

Velocity through the bar screen, m/s

Approach velocity, m/s

thru

0.48

0.6

≤ 0.9

≥ 0.4

Here, velocity = v = 1/n* R²^/³*S⁰^.⁵and Q = vA

In particular, energy savings must be taken care of aeration,

pumping, heating and mixing. In municipal WW treatment,

biological treatment generally requires high-energy consumption

in the range of 50 - 60% of plant usage (8). Thus, energy

consumption is one of the major expenses in operating a WW

treatment plant. Changes in biological treatment processes by

introducing different green technology can significantly reduce

the energy demand at a treatment plant. Chemicals such as

inorganic salts for phosphorus precipitation or sources for

denitrification efficiency and the costs associated with the

collection and disposal of sludge (22) must be considered while

designing the plants. Activated sludge treatment has many

challenges. For examples, activated sludge plants are very

expensive to construct and occupy substantial land areas as well

as require large footprint as per demands. Moreover, sludge is the

residue generated during physical, chemical and biological

treatment. The disposal of excess sludge generated from plant

operation is one of the environmental challenges for wastewater

treatment. The recycling of sludge (containing useful organic

matter and nutrients in agriculture) is considered as one of the best

solutions. Project items such as machines, man power (salaries),

purchases, WWTP construction, administration costs, energy and

maintenance costs, installation and construction costs to be

evaluated for the optimum cost prediction are the major

challenges in WW industry. Adequately trained and certified

individuals must maintain and operate wastewater treatment

facilities. To recruit skilled operator is one of the challenges in

WW industry. The appropriate construction materials selection

under prevailing conditions of exposure to hydrogen sulphide and

other corrosive gases, greases, oil and other constituents

frequently present in WW is one of the challenges for design

engineer. The appropriate selection of metals and paints can

reduce galvanic action. The water pumping, storage, piping,

valves, metering and splash guards’ materials should be specially

selected on the basis of the physical and chemical characteristics

and their interaction to each corrosive chemical. For WWTP,

several additional factors must be considered after solving all

technical or mechanical facilities. First, the challenges from the

plant adaptation should be resolved for different types of

perturbations. Very few WWTPs receive a continuous or constant

influent either in quantity or quality, but are subject to daily,

weekly and annual variations (23, 24). Secondly, the plant

instrumentation, control and automation are always required to

operate the system properly. It is important to measure the

performance of the controller and the degree of adaptability to

different perturbations under certain operating conditions (25).

Thus, the selected alternative must follow the operating variables

within an operating space defined by a set of constraints, which

may be process (biomass, oxygen requirements), equipment

(maximum pumping rates) or safety (effluent requirements)

related. According to Hreiz et al. (2015), WWTPs are facing an

important challenge while trying to achieve optimum design and

operation due to the set-regulatory standards. The designer should

also consider adequate safety measure to satisfy the particular

needs for plant personnel, neighborhood or visitors from hazards.

It increases the construction and operation cost.

Conclusions

To fulfill the water demand in any city is one of the most

challenging tasks. Treated WW could be used as alterative

options for agricultural, gardening, cleaning, industrial

manufacturing, as well as other household purposes. It can reduce

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 7-16

the pressures on other water sources in any region where surface

or groundwater is not sufficiently available. Moreover, some

WWTPs can operate for the production of biofuel or electricity

source (i.e. act as a resource recovery option). To achieve the goal

of best WW treatment, environmental, social, and economical

costs should be considered as factors determining process

selection in light of emerging issues of sustainability. Those

factors can vary with various technological applications during

system design. Environmental issues or social issues should be

evaluated properly prior to the approval of plant design. Social

issues sometimes consider the opportunity cost of spending

money on water treatment as opposed to other community

services.

3. Hreiz R, Latifi MA, and Roche N. Optimal design and operation of

activated sludge processes: State-of-the-art. Chemical Engineering

Journal, 2015; 281: 900-920.

. Wakelin SA, Matt J. Colloff MJ, and Kookana1 RS. Effect of

Wastewater Treatment Plant Effluent on Microbial Function and

Community Structure in the Sediment of a Freshwater Stream with

Variable Seasonal Flow. Applied and Environmental Microbiology.

2008; 74(9): 2659-68.

5. Hasan HA, Muhammad MH, Ismail NI. A review of biological drinking

water treatment technologies for contaminants removal from polluted

water resources. Journal of Water Process Engineering 2020; 33:

01035.

. Antalová V, Slučiaková S, Haluš M. Estimating environmental

benefits of wastewater treatment in Slovakia. 2018: Institue of Env

Policy, Ministry of Environment of the Slovak Republic.

The present manuscript discussed briefly the plant location,

effluent quality requirements, design issues, environmental

impacts, details, and safety concerns. It also highlighted the

necessary flexibility to operate the treatment satisfactorily within

the expected range of influent WW characteristics and flows. The

appropriate design of the various process units of WWTPs would

be based upon the hydraulic, organic and inorganic loading rates.

All units of WWTPs should be hydraulically capable of handling

the expected condition. All piping and channels must be designed

to carry out the design peak instantaneous flows and it can be fully

or partially equalized. Sampling equipment should be installed at

all mechanical plants and it could also be facilitated as needed for

influent sampling and for monitoring of plant performance.

In conclusion, the designer should accommodate the safety

facilities while constructing the plants or performing the plant

operation. The protective equipment (e.g. self-contained

breathing apparatus, protective clothing, gas detection equipment,

goggles, gloves, hard hats, steel-toe safety boot and safety

harnesses) are always be available for employees. Moreover, the

appropriately placed warning signs, adequate ventilation, all

health and safety issues must be included to ensure safe operation

at the construction site.

7. Ouda OKM. Treated wastewater use in Saudi Arabia: challenges and

initiatives. International Journal of Water Resources Development.

2016; 32(5): 799-809.

. Davis ML. Water and wastewater Engineering: Design principles and

practice. 2011: McGraw-Hill Education, 2 Penn Plaza, New York,

USA. ISBN 978-007-128924-5.

. Seneviratne M. Wastewater Treatment Technologies. 2014: ZDHC

Publisher.

0. Ministry of the Environment. Design Guidelines for Sewage Works.

Chapter 8: Design Considerations for Sewage Treatment Plants.

Ontario, Canada. 2008: Ontario Ministry of the Environment. ISBN

978-1-4249-8438-1.

1. Royal commission environmental regulations. Volume I:

Environmental Control Department. 2004: Kingdom of Saudi Arabia.

2. General Environmental Regulations and Rules for Implementation.

001: Kingdom of Saudi Arabia Presidency of Meteorology and

Environment.

3. Abugdera AF, Faris BM, Abugderha MM. Analytical Study of

Environmental Impact Assessment for a Wastewater Treatment Plant

in Sabratha Libya. International Journal of Scientific and Engineering

Research. 2018; 9(5): 199. ISSN 2229-5518.

4. Abaza H, Bisset R, and Sadler B. Environmental Impact Assessment

and Strategic Environmental Assessment: Towards an Integrated

Approach. UNEP.

2004:

http://www.unep.ch/etb/publications/EnvImpAss/textONUBr.pdf.

Ethical issue

15. Azad AS. Design of primary sewage treatment plant. Madras

Agricultural Journal 1995; 81(5): 272 – 273.

Authors are aware of, and comply with, best practice in

publication ethics specifically with regard to authorship

6. Besnarek W, Tkaczyk P. Waste water treatment and disposal.

Agricultural journal. 2001; 50 (72)

(

avoidance of guest authorship), dual submission, manipulation

7. Singh A. Design of Primary Sewage Treatment Plant. M.Tech

of figures, competing interests and compliance with policies on

research ethics. Authors adhere to publication requirements that

submitted work is original and has not been published elsewhere

in any language.

Thesis. BIT Mesra Campus, Allahabad, India. 2011:

https://www.academia.edu/6078256/design_of_primary_sewage_tre

atment_plant

18. Qasim, SR. Wastewater Treatment Plants: Planning, Design, and

Operation. 1998: CRC Press. ISBN 9781566766883.

9. Teklehaimanot GZ, Kamika I, Coetzee, M A A, Momba MNB.

Population Growth and Its Impact on the Design Capacity and

Performance of the Wastewater Treatment Plants in Sedibeng and

Soshanguve, South Africa. Environmental Management. 2015: DOI

Competing interests

The authors declare that there is no conflict of interest that

would prejudice the impartiality of this scientific work.

0.1007/s00267-015-0564-3.

0. Alsina XF. Conceptual design of wastewater treatment plants using

multiple objectives. PhD Thesis. 2008: Department of Physics and

Environmental Technology, University of Girona.

1. Copp J. The cost simulation benchmark. Description and Simulator

Manual. 2002:Office for Official Publications of the European

Communities, Luxembourg.

Authors’ contribution

All authors of this study have a complete contribution for data

collection, data analyses and manuscript writing.

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