Rubber trees (Hevea brasiliensis) are mainly cultivated in Southeast Asian countries especially Thailand, Indonesia, Vietnam, and Malaysia since the 19th century. These countries supply about 70 to 80% of the global natural rubber production. Furthermore, as second largest natural rubber producer worldwide, Indonesia supplied about 26% of natural rubber to the global market in 2013. Meanwhile, due to the rapid industrial and economic development, some changes in land usage occurred in middle 1980’s and therefore large plantation were converted for industrial, commercial, and residential uses. In addition, large quantities of wastewater are presently produced by rubber processing factories in Asia and Africa, this discharge to soil and water bodies poses a lot of environmental danger [1–5].
Moreover, processing of natural rubber consumes a large quantity of water, in addition to some chemicals. The considerable amount of wastewater generated along with effluents are toxic and equally have strong colors, low pH, high suspended solids, temperature, chemical oxygen demand (COD), and biological oxygen demand (BOD) . These characteristics have increased the importance of treating raw rubber processing wastewater before being disposed into water bodies. The liquid waste from this activity do not only contain high organic substances, but high nitrogen pollutants as well . These, liquid waste contains other components including organic matter especially sugar, protein, lipids, nitrogenous, and additional compounds specifically sulfates and heavy metals.
The conventional rubber industry wastewater (RIW) treatment facility needs a large processing area, due to time involved and odor factor. Furthermore, most factories have an open-type wastewater treatment systems due to the low operating costs and ease of maintenance . Therefore, the environment ought to be protected through recycling and therefore a combination of two or more advanced treatment wastewater processes has been proposed [8–10]. The processing of RIW is currently done using conventional methods especially coagulation and ozonation , aerobic and anaerobic bacteria , adsorption and membrane technology [12–15]. This method has been replaced by membrane-based processes especially ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) which is known to be highly effective for water reclamation without consuming much chemicals.
A few studies to reduce the contaminant parameters of the RIW have notably been performed by researchers. The integration of NF membrane and evaporation technologies to treat rubber wastewater show that the use of retentate from NF has improved feed water and evaporators capacity with 55% reduced energy cost . Meanwhile, application of aerobic granular sludge for RIW treatment was reported to have removal efficiencies of about 96.5% COD, 94.7% ammonia-nitrogen (AN) and 89.4% total nitrogen (TN) at the end of the granulation period . Previous study have examined the treatment of RIW using pilot-scale up flow anaerobic sludge blanket (UASB) and downflow hanging sponge system combined with a baffled reactor in addition to settling tanks . The results therefore indicated UASB reactors achieved a total removal efficiency of 39.0 to 72.2% for COD and 67.5 to 88.1% for BOD. In addition, the system proposed about 92% and 80% reduction of greenhouse gas emissions and hydraulic retention times respectively.
The application of direct contact membrane distillation in the RIW treated decreases total organic carbon (TOC), sulfate, color, turbidity, conductivity and TDS by almost 96% . Previous study on the use of palm oil mill effluent (POME) for water reuse when combined with UF and RO membranes showed turbidity and BOD5 were reduced by about 99% and 98.9%, respectively . The final permeates of RO were noticed to comply with standards for water reuse. In addition, the combination of UF and RO method was concluded to be a viable alternative with great potential for use in palm oil industries.
A recent study shown when the RIW treated by sand filtration, cartridge filtration, UF, NF and then RO membranes successively produce the permeate was much better than biological treatment. The removal efficiencies of BOD and COD in this process exceeded 99%, while TN and AN were leveled at 93% .
The adsorption method is equally a prevailing technique for removal of contaminants from liquid waste due to the simplicity and effectiveness in treatment of industrial effluents. The increased number of publications on adsorption of toxic compounds by adsorbents, is a sign of enhanced interest in synthesis of new low-cost adsorbents for water treatment [18–26].
CCR is a solid waste product from acetylene production and popularly used as a raw material for polyvinyl chloride (PVC) synthesis where 1.5–1.9 tons of CCR was obtained while manufacturing 1.0 ton of PVC. This by product is also released by welding processes and mainly comprises calcium hydroxide, a highly alkaline (pH > 12) substance ,.
Meanwhile, CFA is a particulate by-product generated from coal combustion in power plants and often used as a construction raw material  due to the residue’s chemical and mineralogical composition. The compound is a cheap and abundant aluminosilicate source for producing valuable pollutant adsorbents including zeolites, catalysts, photo-catalysts, and geo-polymers. Many studies have also identified these substances as efficient and cost-effective alternatives to remove aqueous and gaseous pollutants, as well as for mercury adsorption , radioactive-isotope and rare element separation , geo-polymer synthesis , acid mine drainage treatment , coking wastewater treatment , and crude oil purification (32). Furthermore, related research disclosed these CFA based materials were potential wastewater remediation adsorbents and membrane filters .
Bentonite is a volcanic ash clay comprising mainly montmorillonite (a smectite crystal with two tetrahedral silica sheets and a central alumina octahedral layer structure). The mineral may be used as a sorbent in waste water treatment with or without prior modification . These chemical alterations are possible due to the surface water molecules plus exchangeable cation interlayer configuration  and are applicable in heavy metal cationic exchange including copper, tin, cadmium, zinc, and iron removal .
Therefore, this study’s purpose is to combine these adsorbents with sand filter and a hybrid membrane UF/RO to decrease effluent COD, BOD, TSS, AN, TN, and turbidity levels as well as to increase pH and RIW quality.