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Advanced technologies for poultry slaughterhousewastewater treatment: A systematic review

Bakar Radhi Baker, Radin Mohamed, Adel Al-Gheethi & Hamidi Abdul Aziz

To cite this article: Bakar Radhi Baker, Radin Mohamed, Adel Al-Gheethi & Hamidi Abdul Aziz(2020): Advanced technologies for poultry slaughterhouse wastewater treatment: A systematicreview, Journal of Dispersion Science and Technology, DOI: 10.1080/01932691.2020.1721007

To link to this article: https://doi.org/10.1080/01932691.2020.1721007

Published online: 08 Feb 2020.

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Advanced technologies for poultry slaughterhouse wastewater treatment:A systematic review

Bakar Radhi Bakera,b, Radin Mohameda , Adel Al-Gheethia , and Hamidi Abdul Azizc

aMicro-Pollutant Research Centre (MPRC), Department of Water and Environmental Engineering, Faculty of Civil & EnvironmentalEngineering, Universiti Tun Hussein Onn Malaysia, Batu Pahat, Malaysia; bDepartment of Structures and Water Resources, Faculty ofEngineering, University of Kufa, Kufa, Iraq; cSchool of Civil Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia

ABSTRACTThe current review aims at improving the understanding on the treatment frameworks related topoultry slaughterhouse wastewater (PSWW) treatment efficiency. Technologies used for nutrientand organic removal during the last 10 years are discussed in this article. The selection of specifictreatment is dependent on the characteristics of wastewater, existing treatment cost, and compli-ance with regulations. The reverse osmosis (RO) technology, dissolved air flotation (DAF), and inte-grated fixed film activated sludge (IFAS) are among the technologies that can produce high-quality treated effluents. DAF is known to have the ability to remove 98.6% of biochemical oxygendemand (BOD) and 97.9% of chemical oxygen demand (COD) while RO can only remove up to90.0% and 97.9% of total nitrogen (TN) and COD. The anaerobic sequencing batch reactor(ANSBR) technology efficiently gave 90% of TN and COD removal. However, gaps and limitationshave been recognized in regards to TP removal. Advanced technologies are considered successfulin terms of water recycling and reuse and waste reduction in poultry slaughterhouses that canoffer a more cost-effective waste management.

GRAPHICAL ABSTRACT

ARTICLE HISTORYReceived 21 September 2019Accepted 19 January 2020

KEYWORDSModifications treatment;poultry slaughterhousewastewater; activatedsludge; growth process;composite fiber

1. Introduction

Global demand for poultry has increased with overallincrease in the global food demand. According to FAO,[1]

the poultry meat production in 2009 was 92.2 milliontonnes (MT) and has increased to 107.0MT/years in 2017.In 2023, the production is expected to increase by 10%[2]

(Figure 1). Processing section of poultry industries createsa huge amount of poultry slaughterhouse wastewater(PSWW) from the slaughterhouse cleaning facilities,poultry slaughtering, and poultry processing sectors (PPS).Poultry industries consume 24% of the total freshwatercompared to other industries such as food and beverage

industries (Table 1) while more than 29% by a global agri-cultural section.[3,4]

Discharging directly a huge amount of wastewater intowater body might greatly affect the quality of natural water.Eutrophication is one of the adverse effects from thatimproper act on environment; and it occurred as a result ofhigh nutrient loading into water system. The growth of algaein water systems can risk nearby residents and negativelyaffects the fishing.[4,5] In Malaysia, around 61% of poultryslaughterhouses dispose of their wastewater directly intocommunity sewerage systems or into the water body withouttreatment. In contrast, 39% of poultry slaughterhouses treat

CONTACT Radin Mohamed maya@uthm.edu.my; Adel Al-Gheethi adelalghithi@gmail.com; adel@uthm.edu.my Micro-Pollutant Research Centre (MPRC),Department of Water and Environmental Engineering, Faculty of Civil & Environmental Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat,Johor, Malaysia.� 2020 Taylor & Francis Group, LLC

JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGYhttps://doi.org/10.1080/01932691.2020.1721007

their wastewater by using aeration tank, dissolved air flota-tion, lagoon and settlement tank for PSWW before the finaldisposal into the natural water systems.[6]

The current work presents a systematic literature review(SLR) according to Yacob et al.[7] guidelines, which consistof three phases (plan, conduct and document review) andtheir corresponding steps (Figure 2). Related review papersin this field have been focusing on certain aspects of PSWWtreatment and solutions such as the type of treatment, treat-ment methods, and evaluation methods. The current paperoffers a thorough and detailed review of various approacheson PSWW treatment technologies based on removal per-centage (%), final concentrations of the treated effluents (mgL�1), and guidelines and regulations that are feasible at theindustries. A large body of research is consulted in prepar-ation for this comprehensive literature review paper. A totalof 126 article papers from 1998 to 2019 including eightreview papers are covered in this current review. Figure 3shows the number of articles that were reviewed and dis-cussed according to years.

This paper aims to provide guidelines for developingimproved PSWW treatment methods and strategies includ-ing effective integrated solutions. The paper contexts onPSWW treatment technologies prompt such effluents tocomply with guidelines and regulations. It exploits and clas-sifies the common PSWW characterization like nutrient andorganic materials, determines particular target, and recog-nizes appropriate treatment technologies. The review ofPSWW treatment technologies is based on various types of

processes efficiency, an accomplish of standard limits andenvironmental impact. Current technologies including opti-mization and performance aspects of the PSWW treatmentsystem for nutrient and organics removal involving com-bined processes and biological treatment are also addressed.The current review allows us to improve the scope andshape the direction of research on PSWW treatment tech-nologies. Finally, the current review discusses open researchchallenges and issues and provides few suggestions forfuture work.

2. Poultry slaughterhouse wastewatercharacterization

Poultry processing wastewater comprises high level of pro-teins, fats, and carbohydrates that are generated from meatparticles, feathers, skin, and blood residues.[8–10] Theresidual of blood and meat particles, in addition to sanitiz-ing and cleaning compounds, are mainly the sources ofphosphorus which could either be organic and inorganicphosphates.[11] The characteristics of PSWW are tabulatedin Table 2. The contaminants in poultry wastewater aredetermined in terms of biochemical oxygen demand(BOD5), chemical oxygen demand (COD), suspended solids(SS), ammoniacal nitrogen (NH4-H), total phosphorus (TP),and pH. According to the studies in Table 2, the concentra-tions of BOD5, COD, total suspended solids (TSS), NH4-H,total nitrogen (TN), total organic carbon (TOC), TP, totalsolids (TS), and pH exceed the allowable standard limit byWorld Bank (see section 1.3) for wastewater effluent.[12–14]

PSWW shows biodegradable qualities (BOD5/COD) morethan 0.6.[15,16] The TP and TN concentrations are rangingfrom 60–18 and 420–400mg L�1, respectively which repre-sent 10–25 times higher than standard limits according toUS EPA.[17] The demands of COD:N:P ratio or (N to Pratio) are optimum for biological treatment processing.[18]

Figure 1. World poultry production annually by region. MT: million tonnes.

Table 1. Freshwater usage in food industries.

Food industry Usage of water (%)

Poultry processing 24Dairy 13Beverages 12Vegetables 10Fruits 9Oilseeds 8Seafood 3

2 B. R. BAKER ET AL.

3. Poultry slaughterhouse wastewater guidelinesand regulations

Guidelines and regulations are required components in address-ing the environmental impact of PSWW in the industrysystem.[21] The standard limits for the disposal of PSWW setby the World Bank Guidelines,[13] Canada EnvironmentOrganization (2001 and 2012), Australian Environment Council(ANZECC, 2000), Malaysian Environment Quality (2009), andEuropean Communities (CEC, 1999) among others are tabu-lated in Table 3. It has been noted that different countries have

different regulations, vary depending on the category of food,agricultural, and industrial waste/wastewaters.[25–27] Accordingto Table 3, the highest level of standard limits among the pre-sented standards are standards by World Bank while the loweststandard limits are set by Australian Environment Council. Asfor Canadian, the standard limits are set at a wider range.Suitability of the new environmental standards provides extrasource of energy recovery like biogas production from thePSWW treatment through combination of anaerobic–aerobicsystems involving the conversion of PSWW organic materials

Figure 3. An overview of the articles reviewed.

Figure 2. Preferred reporting items for systematic reviews.

JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY 3

(resource recovery) into biogas. Despite the advantages, anaer-obic treatment systems hardly generate wastewater effluents thatcomply with new limitation and standard for wastewater efflu-ent discharge. This is because the degradation of organic matterin anaerobic treatment systems for PSWW is not complete.This shows that anaerobic treatment cannot be used alone.[10,14]

4. PSWW treatment technologies

PSWW treatment plants usually comprise of dissolved airflotation (DAF) system and up-flow anaerobic sludge blan-ket (UASB) reactors as a primary treatment. However, thesemethods have low efficiency for nutrient removal to achievethe standards limit implemented by recent stringent regula-tions. Del Nery et al.[3] and UN Division of SustainableDevelopment[28] claimed that the effluents treated by thetraditional treatment processes should be subjected foradvanced treatment to reduce TN and TP concentrations inthe wastewater for safe disposal. PSWW treatment systemsare categorized in biological treatment, mixed processes andphysicochemical systems.[29,30]

Biological treatment system includes three systems: aer-obic, anaerobic and wetlands. The use of anaerobic and aer-obic systems simultaneously involves many furtherprocesses. Common processes are sedimentation or coagula-tion/flocculation (solids separation from liquor), membranetechnologies and electrocoagulation (EC), with each havetheir own advantages and disadvantages. For example, aer-obic systems work at a higher wastewater rate than anaer-obic systems. Anaerobic systems need simple equipmentbecause there is no need for aeration system. In addition,aerobic system is cost-effective with high removal efficien-cies.[15–17,31,32] Mixed or combined processes such as chem-ical coagulation (CC), EC, coagulation/adsorption process,and anaerobic filter (AF) attached to an aerobic SBR havehigh efficiencies for treating wastewater at low cost.[3,15,16,32]

The physicochemical wastewater treatment includes separ-ation of PSWW into several components based on

sedimentation or coagulation/flocculation process. In thisprocess, the solid particles are separated from the liquid bycoagulation or flocculation and sedimentation process.Thereafter, the pollutants are removed by using membranetreatment or EC.[4,15,25,33,34]

4.1. Primary wastewater treatment (PWWT)

Primary wastewater treatment (PWWT) separates all largesolid particles that are produced during the slaughteringfrom wastewater. Screeners and sieves are generally unitoperations for removal TSS from wastewater. Big size solidsin wastewater ranging from 10 to 30mm diameter are holdon the screener mesh. Wastewater solids that have morethan 0.5mm diameter can use rotary screeners to hold solidsto prevent blocking or clogging the instrumentation.According to Chernicharo,[34] mesh screening can removeBOD5 up to 30% by dissociating solid particles and reducemore than 60% of the PSWW solids. PWWT removes TSSby gravity as a mechanical process[35]; BOD5 by 30% andTSS by 60% and reduces the levels of ammonia from 24.7 to1.5mg L�1.[18,34]

Other PWWT of PSWW includes solid separationmethod by introducing air from the bottom of PSWW influ-ent.[36] Thus, light fat, grease, and solid particles are carriedto the tank surface as a sludge blanket form, where they willconstantly remove scum by scraping method, resulted inremoval of 25.8% COD and 31.6% BOD from the initialconcentrations of wastewater.[37] The TSS is removed duringthe primary treatment by mechanical process by gravity.[35]

He et al.[38] reported that the concentrations of TSS forinfluent slaughtering wastewater are more than 200mg/L;this amount can be reduced by 35% through primary treat-ment. Borowitzka[35] revealed that the ammonia in PSWWreduced from 24.7 to 1.5mg L�1, while nitrate (NO3) andnitrite (NO2) concentrations dropped from 0.29mg L�1 to0.15mg L�1 within 6 days of the treatment period.

Table 2. Characteristics of poultry slaughterhouse wastewater.

Country BOD5 TSS COD AN TN TOC TP TS pH References

China NR NR 2000 NR 160 NR NR NR NR [19]

Canada NR 1164 4221 NR 401 546 NR NR 6.9 [15]

Brazil 750–1890 300–950 3000–4800 16–165 NR NR 16–32 1400–3900 7–7.6 [3]

Brazil 750–1890 800–1800 1003–3000 NR NR NR NR NR 7.1 [20]

Turkey 1209 1164 4221 NR 427 546 50 NR 6.9 [21]

Brazil 4635 NR 11,588 63.66 8.59 NR 48.4 6394 6.9 [22]

Nigeria 1900–2200 2280–2446 3610–4180 NR NR NR 50.3 NR NR [23]

USA NR NR 2319 164.5 NR NR 18.1 2000 6.7 [24]

World Bank 30.0 50 125 10 10 – 2 – 6–9 [13]

Except pH, all values are in (mg/L), NR: not reported.

Table 3. Comparison between limitation and standard by many worldwide agencies for PSWW discharge.

Parameter WB standards EU standards US standards CA standardsa AU standards MY standards

BOD5 (mg/L) 30.00 25.00 26.00 5.00–30.00 6.00–10.00 20COD (mg/L) 125.00 125.00 NR NR 3.00�BOD5 120TSS (mg/L) 50.00 35.00 30.00 5.00–30.00 10.00–15.00 50TN (mg/L) 10.00 10.00 8.00 1.00 0.10–10.00 NRaFor BOD5 and TSS limits in Canadian standards are 5, 20, and 30mg/L in freshwater lakes and slow-flowing streams; rivers, streams, and estua-ries; and shoreline, respectively.

WB: World Bank; CA: Canadian; AU: Australian; MY: Malaysia; TN: total nitrogen; TSS: total suspended solids.

4 B. R. BAKER ET AL.

4.2. Land application of poultry wastewatertreatment (LAT)

Land application is one of the treatment methods after pre-liminary treatment for PSWW involving biodegradablematerials. It can be defined as a direct irrigation of PSWWwithin the agricultural field.[15,39] Such biodegradable mate-rials in land applications are used to support soil nutrientsby directly putting them into earth. Recently, the most com-mercial PSWW treatment systems are open lands becausethis application can be scaled up easily and is comparativelycheap to build.[40] Some lands application is constructed onnon-arable areas to enhance nearby power plants throughcarbon dioxide gas access, while others are built near waste-water treatment plants to easily access nutrient supplies.Currently, a large number of demonstration land applica-tions are under construction in many cities in the world likeFlorida, Hawaii, and New Mexico.[37] The current directionsfocus on the advance production of algal biomass throughoptimization of land application systems.[35,39,41] However,the process depends on the climate change; for instance, inmoderate countries, the land application is not suitable dur-ing the winter season.[39,42] One more disadvantage is thepossibility of soil and groundwater contamination.[37,43] Incontrast, the benefits of field applications include the reuseof by-products from the PSWW and fertilizer source.[39]

LAT is used to support soil nutrients through biodegradablematerials by directly putting them into earth[40] and enhancepower plants nearby through access of carbon dioxidegas[37] and optimize the advance production of algalbiomass.[39,41]

4.3. Physicochemical wastewater treatment processes

There are many methods for physicochemical wastewatertreatment processes (Figure 4), particularly for reducingBOD5, oil, fat, and TSS in PSWW.[33,34]

4.3.1. Solid separation from water (dissolved air flotation)DAF process has been used for food industry wastewatertreatment as a primary treatment to separate suspended par-ticles from wastewater.[3,44–46] Variables for DAF processingsystem can be divided into hydraulic load, rate of recycle,saturation pressure and ratio of air/solids which are

dependent on wastewater characteristics and the effluentrequirements.[46] Del Nery et al.[3] evaluates the performanceof a DAF system for PSWW treatment. The instability ofperformance was observed due to the variability of the efflu-ent characteristics quality in addition to the insufficiency ofthe chemical additions in the DAF system. Therefore, theadvanced quality of DAF-effluent can be accomplished bymanaging the chemical pretreatment and the operating con-ditions of DAF system. Separation of solids from waterusing DAF systems is carried out by bringing air into aPSWW influent, through the bottom of the tank (Figure 5a).

The efficiency of DAF in removing SS from PSWWranged between 38 and 70%, while the removal of fats wasbetween 63 and 95%.[47–49] In contrast, the addition of floc-culants or polymers into DAF might improve the SS and oiland gas (O&G) removal by 99%.[50] The maximum removalof COD and BOD5 of PSWW via DAF process was90%[39,47,50] by pre-treating the PSWW wastewater. Thestudy recorded an improvement in the removal of fats by63–95%. Fonkwe et al.[9] examined DAF system using polya-luminum chloride as a flocculant under 300 kPa effluentpressure for PSWW treatment. The SS removal was 43%,while O&G was removed by 49%. The study revealed that at450 kPa, the removal of O&G reached 99 and 74% SS. DelNery et al.[3] revealed that the removal efficiencies of COD,BOD5, and O&G in PSWW using modified DAF systemwith HRT 24 hours were 97.9, 98.6, and 91.1%, respectively.According to Fonkwe et al.,[9] DAF able to accomplish mod-erate to high NO3

�1 and NO2�1 removal. In contrast, DAF

disadvantages are corresponding to poor TSS separation andregular malfunctioning.[9]

4.3.2. Electrocoagulation (EC)The EC system is an advanced technology used for PSWWtreatment. EC system has been approved as an effectivetechnology for nutrients, heavy metals and pathogensremoval from PSWW by bringing the electric current with-out chemical additive.[20,23,51–53] In this technology, alumi-num (Al) and iron (Fe) are utilized as electrodes. Theprocess requires the generation of small-sized ions with highcharge (M3þ) ions as anodes. Additionally, in acidicmedium, Hþ ions interact with electrodes, or in alkalinemedium with OH ions.[20,52] Figure 5b illustrates the regularEC reactor, consisting of a preliminary settling tank which

Figure 4. Different physicochemical wastewater treatment processes. UF: ultrafiltration; MF: microfiltration; RO: reverse osmosis.

JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY 5

responsible for pretreatment. As a fermentation reactor,peristaltic pump ensures the effluent rise to the electrochem-ical reactor, as a result of pressure (inside the electrochem-ical reactor) by the gravity and pump effect. The effluentreturns to preliminary settling tank which provides fermen-tation to homogenize the dissolved metallic element to passthrough the electrochemical reactor. Bayar et al.[9] examinedthe removal efficiencies of COD and BOD5 from PSWW byusing EC system. The concentrations of BOD5 and COD inthe raw PSWW were 1123 and 2171mg/L, respectively.Thus, the EC system removed BOD5 of 96.80, and COD of85.00%. The efficiency of EC treatment depends on the opti-mization of operating parameters which plays an importantrole in removal of color, BOD5, and COD. Therefore, inmany studies, EC system was optimized using response sur-face methodology (RSM) and factorial level design based onreaction time, current density and influent parameters.

Qin et al.[53] and Awang et al.[54] revealed that the opti-mum conditions were recorded at 55minutes of reactiontime, 30mA/cm2 of current density, and 220mg/L of CODinfluent concentrations at which the removal of color,BOD5, and COD were 96.80, 81.30, and 85%, respectively.One more factor which affects EC system is pH of thePSWW. Studies have indicated that high performance of ECreactor was recorded at low pH[52] (Table 4).

4.3.3. Membrane processes system (MS)Membrane processes system is an alternative option forPSWW treatment. Microfiltration (MF), reverse osmosis(RO) and ultrafiltration (UF) systems are capable to removemacromolecules, particles, colloids, and microorganisms(Table 5).[51,55,56] Borowitzka[35] used UF process to treatPSWW with 68.54mg/L of TN and 181.44mg/L of COD.The study revealed that the maximum removal of COD andTN was 94.52 and 44%, respectively. Almandoz et al.[56]

investigated the effectiveness of ceramic composite mem-brane filter as UF for treating slaughterhouse wastewater.The study recorded high removal efficiency of bacteria 99%,while removed COD and TN by 90.63% and 45.22%,respectively. However, membrane technology is expensive,De Nardi et al.[20] evaluated the performance and effective-ness of the membrane bioreactors process (MF) for PSWWtreatment and assessed the total cost, hydraulic retentiontime (HRT), and removal percentage of TN and TP.

The study stated that the total cost has increased with thehigh contents of TN and TP in the raw PSWW. It can beconcluded that despite the importance of membrane filtertechnology for removing nutrients, it faces the biggest chal-lenges. Membrane can foul in high organic concentratedstreams like PSWW due to the formation of thick layers ofbiofouling onto membrane surfaces. This attachment will

Figure 5. (a) Typical DAF reactor diagram. (b) Regular EC reactor diagram. Adopted from De Nardi et al.[20]

6 B. R. BAKER ET AL.

limit the permeation rate of wastewater via membranes.[58]

Nowadays, membrane process is a very important separationprocess wastewater treatment technology, which becomesincreasingly competitive. Through, application of membranetechnologies as a tertiary treatment of secondary effluent toobtain a high-quality final effluent that can be reused fordifferent purposes.[56]

4.4. Biological processing system (BPS)

The efficiency of aerobic and anaerobic treatment of PSWWdepends on the qualities of PSWW.[24] Both methods areused as decomposers to degrade the organic materials intosimple substrates. Moreover, this technology reduces BOD5

by 90%[37] (Figure 6).

4.4.1. Anaerobic treatment system (AnTS)The anaerobic treatment systems have various benefitsincluding low-level sludge production and high BOD5

removal with less energy for biogas recovery.[16,31] The deg-radation of organic compounds in PSWW during the anaer-obic system by microorganism which converts the organicmatter into methane and CO2. However, the high organicstrength of PSWW might affect negatively the efficiency ofanaerobic process.[9] Therefore, the anaerobic system shouldbe followed by extra post-treatment to remove TP, TN, andpathogenic microorganisms.[33,37] The related higher time-space afford considerably an economic property of anaerobictreatment systems.[37] Hence, the mixing of aerobic andanaerobic processes is likely an alternative to conventionalsystems to meet the current discharge limitations.[33,34,59] Amodified septic tank is considered as a continuously stirredtank reactor (CSTR). CSTR has many baffles and compart-ments in which the PSWW flows from inlet over and undercompartments to outlet (Figure 7). The system enhances thebiomass contact time which leads to the increase in biodeg-radation of organic matter in PSWW and improves theremoval of COD and BOD5 by 91%.[38,60] Cao andMehrvar[61] stated that CSTR of PSWW showed high effi-ciency removal for TOC by 93% within 3 days of CSTRtreatment period. Bustillo-Lecompte et al.[40] tested the effi-ciency of CSTR in treating PSWW with 183.35mg/L ofTOC and 63.38mg/L of TN. The system reduces TOC by51% and TN by 88%. Tong et al.[19] developed CSTR as apilot-scale anaerobic–aerobic PSWW treatment process toenhance COD and TN removal. The system recorded thatthe COD removal efficiency was higher than 98% and TNsatisfied with the forthcoming USEPA discharge standard of25mg/L. On the other hand, if TOC amounts were removedat low or medium level, the CSTR as a single system can be

comparable to a combined system in economic expressiondue to the increase in electricity costs. Therefore, productionof biogas is an important issue for energy recovery that willbe understood as cost savings for poultry slaughterhousetreatment plant based on PSWW characteristics.[22,62]

Anaerobic filtration chambers (AFC) is another biologicaland physical treatment systems used for PSWW wherewastewater flow moves over the biological fixed-bed reactorswith filtration compartment (Figure 7b). The mechanismsfor the removal of organic material take place as a functionof the filtration compartment. The particles (biomass) areheld inside and then affixed to the surface filter. Therefore,AFC system is applied as secondary treatment because ofhigh recovery rates of biogas and high removal of solid par-ticles. Whittaker[60] studied the influence of high and mod-erate temperature conditions in the AFC reactor on thetreatment of PSWW. The study revealed that over 90% ofremoval efficiency for COD was achieved under moderatetemperatures, while 72% of the removal was recorded underhigh temperature conditions. Rajakumar et al.[63] reportedthat AFC reactor performance for treated PSWW was likelyto be influenced by low flow velocity at moderate tempera-tures conditions (>35 �C). The findings show that theremovals efficiency of COD is 79% when 10.05 kg/m3 dailyorganic loading (OL) at 12 hours HRT. Moreover, themethane production ranges from 46 to 56%. Oyanedel-Craver et al. and Mancl et al.[64,65] have highlighted the per-formance of AFC reactor for PSWW treatment. The studyindicates that over 80% of COD was reduced whilst 90% ofTN was reduced at the first day of the treatment process.

Anaerobic lagoon (AL) is a common and popular methodin the regions where field and weather availability allow thestructure of ALs to treat PSWW.[37,66,67] The wastewaterinlet from the lagoon bottom is mixed with gas. AL depth isranged from 3 to 5m and from 5–10 days HRTs. The litera-ture claimed that AL removed 97% of TSS, 96% of COD,and 95% of BOD5.

[13,37,52] The main disadvantage of AL sys-tem is the weather conditions and odor production.However, AL is considered as low operation and mainten-ance costs and an efficient choice to treat high organicwastewater, since mechanically, ALs is simple and can becontrolled by nonprofessionals.[68,69] ALs are applied inmany countries such as Canada, the United States, Malaysia,Thailand, India, Vietnam, China, and Germany (UNDivision of Sustainable Development, 2000). US EPA[17]

indicated that ALs removed 87% of BOD5 and SS by 80%.The production of methane was estimated to be 0.5 m3/kgBOD5. Moreover, the covered ALs might achieve high bio-gas quantities with high BOD5 loading.[70] In Malaysia, thecovered ALs construction with enough durability to standwind and higher rainfall rates must be costly.[6] Nonetheless,

Table 4. The treatment technology based on EC.

Removal percentage (%)

Advantages Disadvantages ReferencesBOD5 TN COD

NR NR 85% Effective technology for removing nutrients,heavy metals as well as pathogens.

Without chemical additive.Capable to remove particles and colloids.

The efficiency of EC treatment depends on theoptimization of operating parameters.

Highly affecting by pH.High operation and maintenance costs.

[9]

81.30% NR 85% [53,54]

NR NR 85% [52]

97% 84% 93% [52]

JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY 7

the ALs depend on the weather temperature; for instance, inNorth Canada, the average temperature obtained in ALsranges from 0 to 8.5 �C during the winter.[6] The sensitivityof anaerobic bacteria becomes higher when temperature rap-idly changed. As a result of these changes, ALs almost areimpossible to fail throughout a winter season.

The anaerobic sequencing batch reactor (ANSBR) isanother method used to treat PSWW. The method has lowoperation and maintenance cost. The reactions inside thereactor, settling, decanting and feeding phases take placewithin one tank. However, the mixing process happens inthe cycle reaction.[37,47,71,72] Furthermore, to optimizeANSBR performance, a sporadic feeding of PSWW influentis needed for a recycling wastewater stream.[47] A schematicdiagram of reactor is introduced in Figure 7c. Anaerobicsludge blanket up-flow reactor (ASBUR) is similar toANSBR. The mechanism of ASBUR process depends on thebacterial attached to the granules. The PSWW enters fromthe bottom of the reactor, the influent filled the sludge blan-ket and follows inter this wastewater to biomass film.Finally, the wastewater comes out from the top of reactor.Fundamentally, ASBUR includes three main phases: firstly,influent as PSWW; secondly, film as biomass; finally pro-duced methane gas on digestion.[3] According to the sameauthor (refs), ANSBR treatment for slaughterhouse waste-water under HRT 1 day and OL of 10.05 kg/m3 day gave95.8% of COD removal, 94.0% of BOD5, 50.5% of TP and61% of TN. Caldera et al.[73] uses ASBUR to treat PSWW atmesophilic and thermophilic conditions. The initial concen-trations of COD ranged from 1820 to 12,790mg/L, the sys-tem reduced COD by 94.31% within 1 day of the treatmentperiod (HRT) under the OL rate of 9000mg/L day.Moreover, Sarti et al.[14] investigated the efficiency ofASBUR for treating PSWW as a function of OL (31,000mgL�1), temperature (25–39 �C), and HRTs (3.5–4.5 hours).The study shows that ASBUR exhibited 95% of BOD5

removal. Li et al.[37] evaluated the performance of ASBURfor tearing of PSWW with COD between 1400 and3600mg/L. The system removed 70% of COD during thetreatment process at various OL rates and feeding condi-tions. Fongsatitkul et al.[23] assessed the performance ofASBUR for PSWW treatment with raw wastewater concen-trations of 5000mg/L COD and 360mg/L TN with 6 hourcycles. The efficiency removal of COD was 95% and 95% forTN. Therefore, anaerobic treatment systems have comehandy with low OL rates, and can be recognized as a gooddegradation and pollution control processes show goodoverall results as complimentary treatment.

4.4.2. Aerobic treatment system (AeTS)In aerobic treatment units (ATUs) system, aerobic microor-ganisms are causative organic materials removal in the oxy-gen (O2) existence. The amount of O2 and treatment periodfor this system can be increased with high strength ofPSWW. ATUs are usually applied as the last nutrientsremoval using anaerobic techniques.[42] There are severalconfigurations of aerobic reactors such as aerobic SBR andactivated sludge (AS). Nevertheless, the biological treatmentTa

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Removal

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75–96

83–97

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MF

44.81

90.63

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:pressure;T:temperature;v:velocity.

8 B. R. BAKER ET AL.

system is identically similar, and must be determined ifnitrogen (N2) is involved.[16,17] In ATUs system, 88% ofammonia can be oxidized.[4] Aerobic system digestions forshort-time attained a better flocculability of sludge. Also, ithas higher biomass reusability and retention, higher micro-bial density with millions of bacteria cells per gram of bio-mass, and broader selection of bacterial strains for plausiblebio-augmentation.[25] ATUs are commonly employed forremoval of nutrients after using anaerobic techniques andfor final decontamination.[25] However, the biological pro-cess is very similar, and being necessary to define if nitrogenremoval is required.[23] Aerobic reactors may have severalconfigurations. Many authors demonstrated that usingATUs with stacked configuration in treating high strengthPSWW is advantageous due to minimal space requirements,low capital cost and excellent COD removal efficiencies(around 83%).[16,25]

AS system is widely used for industries and municipalwastewater treatment (Figure 8). The main purpose of ASsystem is to eliminate insoluble and soluble organics mater-ial from the wastewater[37,74] and to improve the settlementprocess.[15,17,32] However, poor settling flocs recorded inPSWW might be due to the fat contents and low levels ofdissolved oxygen (DO). Therefore, the PSWW treatmentprocess should be aerated to reduce the sludge product.[39]

Pab�on and G�elvez[75] investigated a full-scale 144,000 L ofAS reactor to remove BOD5, COD, and TSS from rawPSWW and obtained 5242, 9040, and 2973mg/L of initialconcentrations, respectively. The maximum removalachieved was 89.73% for BOD5, 89.03% for COD and94.09% for TSS with HRT 2-day and wastewater influentrate of 1.38 L/s.

Fongsatitkul et al.[23] studied the AS system to treatPSWW effluent using two 10 L reactors in parallel, continu-ous flow, and internal recycle. Among these full-scale sys-tems, two reactors achieved removal efficiency up to 97.60,89% for COD and TP, respectively, while total Kjeldahlnitrogen (TKN) was removed by 81.50%. Bustillo-Lecompteet al.[18] assessed the performance and costs of AS processfor removal of TOC and TN from PSWW. Influent

concentrations of TOC and TN were 1009 and 254mg/L,respectively. The study showed that AS process removed73.46% of TN and 95.03% of TOC with 254mg L�1 of TNand 1009mg L�1 of TOC in the raw PSWW. In contrast, atinitial concentrations of 144mg/L for TN and 639mg/L forTOC, the highest TN removal was 75.15%, and TOC was94.26% after 8 days of HRT. It can be concluded that theincrease in organic removal rate occurred at a constant aer-ation basin DO level, as a result to proliferation of filament-ous microorganisms.[57] These organisms grew beyond thegeneral limits of the flow into the bulk solution and causedsludge bulking. The decreasing wastewater discharge resultedin the reduction of the filamentous microorganisms and theproduction of a non-bulking sludge.

Aerobic sequencing batch reactor (ASBR) is a systemwhich involves filling, reaction, settling, drawing, and idlestage. Fongsatitkul et al.[78] reveals that the ASBR removed95% of COD and TN from PSWW. Li et al.[79] evaluatedthe effect of aeration on nutrients and organic contentremoval from PSWW at room temperature for 8 hours. Theinitial concentrations of TN and COD were 350mg/L and4000mg/L, respectively. The study showed that higher aer-ation amount (0.4 L/min) increased the removal efficienciesof COD and TN to 90 and 34%, respectively. In contrast, at0.8 L/min of aeration, the removal of COD was 97% and95% for TN. Koide et al.[41] and Seviour et al.[32] reportedthat the removal efficiencies achieved by ASBR (6 hourcycles) for COD, TP and TN were 95%, 98%, and 97%,respectively. Peng et al.[80] studied a 5 L ASBR full-scalemixed with suspended growth biomass for PSWW nutrientsand organic content. The central composite design (CCD)program at 16 hours cycles was used for optimal conditions.The system removed 85.91% of TN and 62.13% of COD.Kundu et al.[81] considered ASBR system for treatingPSWW in a laboratory-scale. The raw concentrations of TNranging between 90 and 180mg/L, and between 950 and1050mg/L for COD. The study recorded 95% of CODremoval after 8 hours and between 74.75 and 90.12mg/L ofTN. Rajab et al.[5] studied the performance of ASBR fortreating PSWW (high-strength wastewater) with initial

Figure 6. Different biological treatment processes. S: substrate concentration available to microorganisms; Sbulk: substrate concentration in the bulk of the liquid;CSTR: Continuously stirred tank reactor; AFC: anaerobic filtration chambers; AL: anaerobic lagoon; ANSBR; anaerobic sequencing batch reactor; AS; activated sludge;ASBR: aerobic sequencing batch reactor; ASG: aerobic suspended growth configuration; AGBR: attached growth bioreactor; IFAS: integrated fixed film acti-vated sludge.

JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY 9

Figure 7. (a) Regular CSTR bioreactor diagram example. (b) Regular AFC reactor diagram. (c) Regular ANSBR reactor diagram.

10 B. R. BAKER ET AL.

Figure 8. (a) Regular AS reactor diagram. (b) Schematic diagram of IFAS (Del Pozo et al.[76]) (c) Schematic diagram of SB (Aziz et al.[77]).

JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY 11

concentration of 1500mg/L for BOD5, 2010mg/L for COD,and 110mg/L for NH3-N and within 24 hours of HRT. Thesystem removed 97% of BOD5, 95% of COD and 90% ofNH3-N. Based on the above-mentioned studies, it was notedthat ASBR has high efficiency to improve the quality ofPSWW and reduce the COD and TN to meet the standardlimits required for safe disposal.

Aerobic suspended growth configuration (ASG) isanother aerobic system which has been used for treating ofPSWW. However, the system is comparatively sensitive andneed skill to control operation activities and free from bulk-ing.[60] SBR is one of the advanced technologies in the aer-obic suspended growth treatment system.[4,36,82,83] Irvineand Moe[84] examined the efficiency of ASG to treat slaugh-terhouse wastewater with 1100mg/m3/day of COD 5days ofHRT within 6 months of treatment period. The studyshowed 67% of BOD5 and 55% of COD removal. The studyalso compared between SBR at 800mg/L/day of COD load-ing for COD and BOD5 removal/day. The results showed66% of COD removal and 92% of BOD5 with HRT 24 hours.Mohan et al.[85] studied a full-scale ASG in SBR at 26–28 �Cand with 24 hours of HRT pH of complex organic waste-water was adjusted to 7.1 ± 0.2, the DO was maintained inthe range of 3.0– 4.5mg/L. The study established that SBRperformance is conditional with OL rate. Moreover, the sys-tem resists its performance up to 1.7 kg/m3/day of COD andabove 3.5 kg/m3/day of COD loading rate showed that thesystem performance was limited.

The attached microorganism-based system which is usedto treat PSWW is called attached growth bioreactor(AGBR). The concept for applying acrylic-fiber biomass car-rier lies in the manipulation of the capacity of organismsand the ability to grow on several surfaces.[86,87] The

organisms responsible for the transformation of organicmaterials and other constituents are “attached” on someunmoving solid surfaces or fixed films.[88–90] The system hassome advantages such as low requirement of energy andoperating costs besides its simplicity, minimization is neededfor settling capacity, and smaller reactor volume.[91–93] Thesystem is more suitable for treating high-strength wastewatersuch as PSWW due to higher biomass concentrationsattached to the reactor.[44,94] Fonkwe et al.[8] evaluatedAGBR as a primary treatment for synthetic PSWW. TheAGBR was designed to reduce the effect of suspended solidson membrane fouling in the bioreactor. COD and TN con-centrations in the raw PSWW was 250mg/L and 23.9mg/L.The study reported that the maximum removal of COD was95% while was 90% for TN. Qiao et al.[95] used AGBR totreat high-strength organic wastewater effluent using swim-bed technology with 12,000mg/L of COD. The attachgrowth reactor achieved removal efficiency of 80% for CODwithin 3 hours of HRT.

The integrated fixed film activated sludge (IFAS) is themodification of conventional AS. It has been applied tomeet more stringent environmental regulation. The inte-grated IFAS is one of the popular and relatively new tech-nologies which has been introduced in the last 15 years(Figure 8b). The system depends on a moving bed biofilmreactor, in which solid media is suspended plastic pieces orfixed synthetic mesh are added to suspended growth reac-tors to provide attachment surfaces for biofilms.[63,95,96] Thetechnology combines between conventional AS process andattached growth process. IFAS has several advantagesincluding larger process stability, reduced sludge productionand reduced solids loading on the secondary clari-fiers.[2,90,97,98] The IFAS procedure incorporates the sus-pended activated sludge (SAS) processes and fixed-film. Inother words, the added mass medium to the aired basinsand a small basin volume makes sludge nitrification to beconsiderably achievable in the nitrification process. In add-ition, mass medium supplies surface area for the develop-ment of microbes.[12,51,99] However, on the last clarifiers, theattached growth does not enforce excessive solids loading,since the microbe development remains in the aired basin.

IFAS system needs no additional operator compared toconventional AS system. MLSS are settled in the last clari-fiers and thickened and brought back as return activatedsludge (RAS) with the exclusion of waste remains needed tobe removed to maintain the age of suspended sludge. Theage of suspended sludge ranges from 4 to 5 days at nearly10 �C to achieve high removal efficiency. Del Pozo et al.[76]

investigated the performance of IFAS system for treatingPSWW with 770mg/L of COD and 84mg L�1 of TN, theIFAS system removed 93% of COD and 67% of TN. Kimet al.[63] used IFAS pilot systems for COD, TN, and TPremoval from PSWW. The influent flow rate was3.8� 103m3/day with COD loading of 390 ± 127mg/L andwithin 22 days HRT. The study revealed that at 8 days ofHRT, 90% of COD was removed, TP decreased to 1mg/L at8th day of HRT. The effluent generated from IFAS systemcontains 3.6 ± 1.2mg L�1 ammonia and 5.1mg L�1 nitrate.

Figure 9. Schematic diagram of CF.

12 B. R. BAKER ET AL.

Swim-bed system (SB) technology system combines anovel support material net-type acryl-fiber biomass carrierknown as biofringe (BF). BF has been used to treat high-rate wastewater (organic wastewater).[4,74,100–102] Swim-bedBF has established an effective treatment of high-strengthorganic wastewater volumetric loadings up to 12 kg/m3/dwith 80% of COD removal within 3 hours of HRT. In swim-bed with BF, the biomass is attached to a flexible matrix ina fixed position medium which enlarges the surface area forreactions to occur.[103] Simultaneously, the moving of amatrix caused by flow of wastewater creates a “swimming”motion that enhances nutrients transfer (mass transfer) tothe attached growth. BF has an aerobic zone near surfaceand anaerobic zone inside sludge, which increases the per-formance of nitrification and nitrogen removal.[4,74,104–106]

Figure 8c shows the schematic of SB system. Wagneret al.[107] evaluated the performance of SB with high-strength OLs containing more than 12,000mg COD/L/dusing the biomass attachment BF. The study reported that80% of COD was removed within 3 hours of HRT.Moreover, up to 133 g/m of BF biomass was held with con-sider to the BF holding. However, a limited improvement ofnitrification was recorded at less than 1600mg/L of CODloading. Baker et al.[62] evaluated a SB fixed-film reactorwith BF and only conventional AS with BOD5 loading653mg/L for PSWW treatment under (25 �C temperatureand pH at neutral 7.0 ± 0.5). The overall COD for SB fixed-film reactor removals were 84.3% for BOD5/COD ratio of67% with 14 days, along with 98.8% of BOD5 removal.

According to Rathour et al.[108] a developed SB systemdual-chamber microbial fuel cells (MFC) treatment systemhas been used for the treatment of several wastewater pollu-tants such as PSWW. In this system, an anaerobic anodicchamber is fed with the substrate for metabolism of

microorganisms, which generate electrons and protons.Electrons are transported through an external electric circuitto the cathode, and protons diffuse to the cathodic chambervia proton exchange separators. PSWW treated in single-chamber noncatalyzed MFC achieved 95.49% COD removaland 99.0% turbidity removal. The MFC systems for waste-water treatment recover inorganic metal pollutants frompollutants (COD or TOC) by power densities. Besides that,MFC systems have several additional advantages over con-ventional wastewater treatment processes, offer a combin-ation of biological (SB) and electrochemical processes, bettertreatment efficiencies, minimum sludge generation, and self-sustainable systems with lower operating costs.

4.4.3. Sequencing batch biofilm with composite fiber (CF)technique (SBBCF)

The regulation for wastewater treatment system prioritizesthe development of wastewater treatment technology toemploy environmentally-friendly and economical systemswith minimal use of chemicals. Therefore, new methods andtechnologies have been rigorously developed for the purposeof achieving effective and efficient pollutants removal. Oneof the latest developments of biological treatment is the useof fixed film with fiber as the biomass carrier.[2,109,110] Theutilization of fiber as a biomass carrier such as biofilmexhibits good performance in removing pollutants especiallynutrition substance.[2,111–113] For this reason, developmentto seek new materials that are able to offer good removalefficiency of organic, nitrogen, and phosphorus contents atconsiderable cost is highly promoted. Furthermore, there isyet an attempt to employ composite fiber (CF) in this tech-nology so far. The prospect of using this type of biomasscarrier is very high and the technology is relatively new. In

Figure 10. A schematic diagram of ADTS reactor in PSWW treatment.

JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY 13

response to the problems, new technology via CF to reducethe wastewater contamination has received much interestworldwide. By using this type of biomass carrier, animprovement in the settling characteristics was achieved inthe reactor. According to this approach, through wastewaterflow, a flexing of the matrix creates a swimming motionthat enhances mass transfer of nutrients to the attached bio-mass.[25,114] Moreover, this swimming motion enhances sep-aration of excess biomass which causes formation of a densesludge floc.[2,115] In fact, a sludge settling properties couldbe improved by employing the CF material as a biomasscarrier. The reduced SVI value gradually decrease MLSS atthe same time, indicating that increase in the attachedsludge on the CF material.[77,116]

CF as a biomass carrier is a highly efficient contactmaterial that keeps a high volume of bacteria externally andinternally and never releases bacteria all the time whenreactor run.[39] There are many advantages when combiningCF as a biomass carrier (adhesive) with swim bed technolo-gies such as high processing performance, less space, lesssludge produced, no need for additional chemical for coagu-lation pretreatment even for high suspended solids and con-centrations of oil due to the longer retention time ofsludge.[25] Figure 9 shows the schematic of CF technique. Itshows that the volume of reactor tanks was 10 liters. It wasmade from Plexiglas material. Three CF sheets were installedinside the aerobic reactor tanks. Air was added into an oxictank by three air nozzles using air pump. DO was approxi-mately 0.5mg/L. Airflow was adjusted by an airflow meter.CF technique reduced sludge production and solids loadingsin comparison to the conventional wastewater treatment.This is because the composite fiber providing oxic zone atperiphery and anoxic zone inside sludge, which increasesthe performance of nitrification and nitrogen removal.[74,80]

In swim-bed CF, large amounts of biomass are attached to aflexible matrix in a fixed position medium which enlargesthe surface area for reactions to occur. The flexing of matrixis induced by wastewater flow creating a “swimming”motion that enhances mass transfer of nutrients to theattached growth. CF has an aerobic zone near surface andanaerobic zone inside sludge, which increases the perform-ance of nitrification and nitrogen removal.[25,74]

4.5. Advanced processing system (APS)

Recently, advanced processes have been encouraged forPSWW treatment to remove a large amount of organic pol-lutants. These methods have several advantages like easyoperation, small production of sludge, low consumption ofenergy, and environmentally compatible.[23]

4.5.1. Electrochemical advanced oxidation processes(EAOxP)

Electrochemical oxidation processes (EAOxP) are the modi-fications of electrochemical processes to meet a new strin-gent regulation. The EAOxP is new and one of the populartreatment technologies. The system depends on the electro-Fenton process, where Fenton reaction, hydrogen peroxidereacts with Fe to produce ferric ions and hydroxyl radicals.The hydrogen peroxide is added to degrade the harmfulcompounds in this process. This technology has severaladvantages include reduce sludge production and moretreatment stability.[117] According to Davarnejad andNasiri,[117] the optimum conditions for EAOxP system usingRSM software program were found at 4.38 pH, 55.60minutesreaction time and 74.07mA/cm2 current density removedCOD at 92.37%. Also, at pH 3.39, 49.22minutes reactiontime, and 67.90mA/cm2 current density, the removal ofcolor obtained was 88.06%. EAOxP was also investigated byDe Sena et al.,[118] who reported the effect of reaction time,pH, current density (CD) and volume, also on COD andcolor removal. The researcher detected that optimum condi-tion was 55.60minutes reaction time, 4.38 pH, 3.73H2O/Fe2þ molar ratio, 74.07mA/cm2 CD, and 1.63mL/L volumeratio for 92.3% COD removal. The optimum condition for88.0% color removal was 3.39 pH, 49.22minutes reactiontime, 3.62H2O/Fe

2þ molar ratio, and CD of 67.90mA/cm2.

4.5.2. Anaerobic digestion treatment system (ADTS)The anaerobic digestion treatment system (ADTS) is anotheradvanced method for PSWW treatment. The method alsoproduces biogas. The digestion and biogas production takeplace within one tank (batch-fed anaerobic co-digestionreactors). However, this process is a part of biochemical

Figure 11. A schematic diagram of EGSB reactor in PSWW treatment.

14 B. R. BAKER ET AL.

process which decomposed a complex organic compound inthe absence of oxygen by anaerobic microorganisms.[37,47,119]

Latifi et al.[119] optimized ADTS performance, the effective vol-ume of reactors (0.5–0.7 L) that were feed with wastewater, has27 g total volatile solids (TVS). The reactor was vacuumedusing vacuum pump to inject nitrogen (N2) gas at the upperreactor to create a new environment (anaerobic) and take outthe remaining air. The researchers installed circulation systemwith water bath to keep the reactor temperature at 34 �C. Aschematic diagram of reactor is introduced in Figure 10.According to the same author, ADTS treatment for slaughter-house wastewater was conducted under 50days of retentiontime at 34 �C. Also, inoculum-substrate ratio (ISR) of 4 and TSof 5% at a larger scale (20L). The production of methane andbiogas were recorded to be 0.402 and 0.574m3/kg, respectively,and the digester leads to 63% VS removal and 88% CODremoval. Christian et al.[120] reported on the high-strengthwastewater treatment. This anaerobic digestion with membranebioreactor has an effluent design of 475,000L/d with39,000mg/L COD, 18,000mg/L BOD, and 12,000mg/L TSSloadings. The anaerobic digestion with membrane bioreactorgiving COD and BOD removals efficiency of 99.4% and 99.9%at the concentrations of 210 and 20mg/L, respectively.

4.5.3. Expanded granular sludge blanket reactor (EGSBR)Due to the EGSBR recirculation stream which is known toincrease sludge expansion for improved efficiency, it wasrecorded that the COD removal achieved 67% for PSWWwithout a pretreatment process.[121] According to Basitereet al.[121] two-stage system of anaerobic digester EGSB joinedwith two bioreactors (anoxic and aerobic) was introduced totreat PSWW. The EGSB consisted of a cylindrical formed witha 1.2 L volume and heights of 0.22m and 0.06m. For solidsand biogas separation purpose, the gas–liquid separator wasinstalled at the top of the reactor column (Figure 11). To opti-mize EGSB performance, the velocity of up-flow reactor waskept at 1.1m/h. The reactor temperature was maintained at37 �C using water from a thermostatic circulating water bath.This gives high COD values of 2–6 g/L, and average BOD andFOG value of 2.4 g/L and 0.55 g/L, respectively. The CODremoval from the system was 40%, 57% and 55% at 0.5, 0.7and 1.0 g COD/L/day of OL rates. At high OLR (1.0 g COD/L.day), the COD removal from EGSB was recorded at 65%.Williams et al.[122] revealed the efficient removal of COD was

48% (min.) and 93% (max.) using response surface method-ology (RSM) to optimize EGSB reactor at OLR 1.01 g COD/L.day (min.), and 4.82 g COD/L/day (max).

4.5.4. Static granular bed reactor (SGBR)The aim of applied SGBR reactor in the PSWW treatment isto reduce the organic load. The SGBR scale consisted of acylinder reactor shaped made from polyvinyl chloride (PVC)with 1.53 L volume and the 0.071m diameter and 0.5867mheight. Other 5L containers were applied to store wastewaterprior to treatment. At the upper of the SGBR, a PVC pipe wasplaced to distribute the entire feed across the reactor. To pre-vent clogging underdrain pipes and granular sludge washout, a5mm diameter pea gravel was used as an underdrain. Also, agrit sieve (2mm) was placed at the bottom of the reactor tohold the pea gravel. Using peristaltic pump, the PSWW wasfed at the top of the reactor. The temperature of reactor rang-ing between 35 and 37 �C. Finally, a 0.50 L plastic bag wasused to collect biogas.[123] Basitere et al.[123] tested the effi-ciency of SGBR in treating PSWW with a range between 1223and 9695mg/L of COD, 2375mg/L of average BOD and554mg/L of average oil and grease (FOG). The system reducedaverage COD by 93%, TSS by 95% and FOG removal by 90%.Debik et al.[124] applied the SGBR system to treat PSWW and85% average COD reduction was observed at an OLR of1.64 kg COD/m3/day. The comparison between PSWW treat-ment technologies is presented in Table 6.

5. Conclusion

Biological treatment technologies are among the approachesfor PSWW treatment. The approach is mainly presented tosuccessfully remove the organic and nutrient materials fromwastewater without the addition of chemicals and cost. Thesuspended biomass is an important factor in selecting anappropriate biological treatment technique because most ofthe methods are used for the PSWW treatment. Which areeffective to remove the suspended solids, organic matter andnutrient loading from PSWW. The BPS is found to be oneof the most efficient treatment technologies. Based on thereview above, it can be concluded that:

� The literature lacks attempt to evaluate, select and extractoptimized features of PSWW treatment technologies to

Table 6. The comparison between PSWW treatment technologies.

PSWW treatment technologies

PWWT LAT

PWWT BPS

SB SBBCFDAF EC MS

AnTS AeTS

CSTR AFC AL ANSBR AS ASBR ASG AGBR IFAS

BOD5 O X X X O X O X X X X O O X X XCOD O X X X X X O X X X X O X X X XTN O X O X O X X O O O X O O O O XTP O X O X X O O O O O O O O X O XTSS X X X O X O X X O X O X X X X XO&G X X X O X O O O O O O O O O X OColor X X X X X O O O O O X X O O O O

X: efficient of removal; O: inefficient of removal.

JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY 15

develop an advanced PSWW treatment, for removal andmitigation methods. The classifiers need to be continu-ously supported with new and updated features toaddress new PSWW pollution threats.

� There is a dominant need to explore the practical andreal utility of PSWW treatment and a need to performmore large-scale field studies that can simulate heteroge-neous and scalable PSWW pollution.

� Research conducted on the removal of contaminantsfrom PSWW using swim-bed system and advance proc-essing system is lacking.

� Most of the reviewed methods are lacking in treatmentmechanisms against the recycling of PSWW.

� Various contaminants and their removal by biologicalprocessing system (BPS) exist based on variety of factorswhich include size of BPS, type of contaminants, initialpH, batch conditions, temperature, hardness, DO, andthe presence of natural organic compounds. So, a moredetailed work on these interactions is needed to obtainfurther insights. Besides, how to use the DO more effect-ively in BPS system is still a question.

� Studies on PSWW treatment processes are mostly carriedout at the lab scale. Most laboratory studies have eval-uated the performance of PSWW treatment technologiesin removing relatively high concentrations of contami-nants. However, conclusions drawn from the lab experi-ments may not reflect the performances at contaminatedsites. Thus, there is a need to perform more large-scalefield studies and to explore the practical utility of treat-ment technologies on commercial scale.

Funding

The authors would like to thanks to the Research Management Centre(RMC), UTHM for providing FRGs Grant (K184) (Modification ofBead Adsorbents with Ceramic Sanitary Ware Waste (CSWW) andChitosan for Laundry Greywater (LGW) Safe Disposal) as a financialsupport for this research project.

ORCID

Radin Mohamed https://orcid.org/0000-0002-2023-9196Adel Al-Gheethi http://orcid.org/0000-0001-7257-2954

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