Field Testing And Performance Evaluation Of River Water Treatment Plants

Biological Process for River Quality Improvement Works.

Among the different approaches that have been proposed in these last decades, the technology known as Moving Bed Biofilm Reactor (MBBR) and Integrated Fixed Activated System (IFAS) as shown in Fig ure 0 1 is successfully applied in the clean-up of wastewaters from urban, industrial and agricultural uses. Currently in Malaysia MBBR and IFAS are customized to suit its application in river water treatment plant (RWTP) under River of Life (ROL) project (Mohiyaden et al., 2016). Currently RWTPs have been monitored by Departments of Irrigation and Drainage (DID) at Klang river and its tributaries. Each treatment work employs unique treatment process with the purpose to improve water quality from existing condition to acceptable quality for body contact recreational purpose (DID, 2012).

Several studies have produced estimates of biofilm growth and IFAS capabilities of removal toward certain contaminants in municipal and industrial wastewater (Æsøy et al., 1998; Regmi et al., 2011; Hoang et al., 2014), but there is still insufficient data for biofilm’s ability to reduce certain amount of pollutant removal for RWTP including turbidity levels.

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Site Description

A research site was constructed starting in the year 2013 for ROL Projects around Wilayah Persekutuan Kuala Lumpur and Selangor State. As shown in Fig. 2 , there are total seven (7) RWTPs with MBBR and IFAS based concept. There are seven RWTP selected for monitoring and testing since these RWTP are monitored by the Malaysian Department of Irrigation and Drainage for River of Life Project. Several types of biological carrier in six (6) different RWTPs will be tested for this study.

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For this study, several types of biomedia were applied in River Water Treatment Plant (RWTP) as a biological process at ROL Project. This study focuses on the evaluation of the biological performance in RWTP. These various removal rates will be evaluated in this study with different biomedia characteristic such as Surface Roughness, Porosity, Pore Size and Specific Surface Area as tabulated in Table 1 . Biofilm detachment at the biomedia will be tested in certified laboratory.

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Sampling Procedure

Sampling schedule differ from each RWTP depend on its design and numbers of available chamber and its operation as well as weather condition. MLVSS sampling are referred based on the Figure 3 .0 below. MLVSS will be tested in Fill Media and Bottle media as illustrated in Figure 1 . The location of the 6 selected RWTP is shown in Figure 2 . 3 samples will be taken in every month for duration 1 year for each RWTP. Overall, there are 180 MLVSS and 84 TVS and 58 turbidity testing samples will be tested for 1-year duration. Sample of selected sampling schedule are summarized based on Figure 4 .

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Water quality samples from Inlet and Outlet, MLVSS and TVS in the oxidation tank of the RWTP were collected as grab samples for once per month as shown in Fig 4. They were sampled into a plastic bottle with capacity of 2 litre and sent to certified laboratory for chemical testing as represented in Fig 3. Besides that, an in-situ water quality probe also installed at the bottom of oxidation tank for measuring the physical properties of the temperature, dissolved oxygen and sludge height to monitor the performance of each plant. Once a month influent wastewater, mixed liquor of the different compartments and effluent

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Analytical Method

MLVSS, TVS and Turbidity test have been conducted from grab water sample. The key compounds required to characterize samples were measured according to the Standard Methods (APHA, 2005).

Solid Test for Suspended and Attached growth system

Two parameters recorded to evaluate the biofilm formation in biomedia. The aim of this test is to determine the types of solids either total solids, total fixed solids or total volatile solids in the water samples. According to Bertino (2010) method, biofilm layer formation is measured using total volatile solid (TVS) parameter. To determine TVS, attached biomass fixed in biomass carriers, all seven sample of biomedia carriers were taken out of the reactor and kept in porcelain dishes or beakers with water.

All seven sample of biomedia without biofilm are initially identified and weighted. The biomedia was moved manually using knife and needle until the attached biomass on the carriers were slugged off from the carriers using recorded distilled water. The GFC Whatman’s 1.2 μm filter paper and porcelain dishes were weighted before filtration. Then the solution of biomass and mL water was filtered through a filter paper. The filter paper and porcelain dishes were then kept in the oven at 105 ºC at least for 1 hour followed by desiccation for 20 min and measured weight as “A”. The filter paper was again kept in a furnace at 550 ºC for 20 min followed by desiccation for 20 min and measured weight as “B”. The average biomass was calculated as the average TVS value of the acclimatized carriers. Total volatile solid is mostly organic matter. TVS were calculated as mention in Equation 1.

$$\mathrm{T}\mathrm{V}\mathrm{S}=\frac{\left[\mathrm{A}\mathrm{}\right]-\left[\mathrm{B}\right]}{\mathrm{w}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{}\mathrm{s}\mathrm{a}\mathrm{m}\mathrm{p}\mathrm{l}\mathrm{e}\mathrm{}\mathrm{v}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{m}\mathrm{e}\mathrm{}\times \mathrm{b}\mathrm{i}\mathrm{o}\mathrm{m}\mathrm{e}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{}\mathrm{s}\mathrm{a}\mathrm{m}\mathrm{p}\mathrm{l}\mathrm{e}\mathrm{}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}}\mathrm{}\mathrm{}\mathrm{}\mathrm{}\mathrm{}\mathrm{}\mathrm{}\mathrm{}\mathrm{}\mathrm{E}\mathrm{q}\mathrm{u}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{}\mathrm{1}$$

Where,

A = Weight of filter and porcelain dish + residue after oven 105°C

B = Weight of filter and porcelain dish + residue after ignition

Turbidity

Turbidity level is a standard parameter measured in the river. This paper will analyse the capability of RWTP to remove turbidity in the river water. Plus turbidity is often tested in many previous research for nutrient removal in many biological process (Boye, Falconer, & Akande, 2015; Deng et al., 2016; Zheng et al., 2011).

MLVSS Result

A set of data of MLVSS for nine (9) month monitoring as shown in Table 1 below.

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Figure 5 shows average MLVSS from November 2017 to July 2017. The highest value of MLVSS ever recorded is RWTP Sg Gisir with value 34.33 mg./L on Jun 2017. Second highest is RWTP Sg Kemensah with 31.00 mg/L on November 2016. Contrary to expectation, average MLVSS results are relatively very low compare to MLVSS content in any activated sludge system (Mannina, Capodici, Cosenza, Di Trapani, & Ekama, 2017). This may due to hybrid IFAS system technology that has been applied in RWTP and this might be biofilm attached growth would be more dominant.

Although these unsatisfactory MLVSS value outcomes differ from some published IFAS studies, there are several possible explanations for this result. Most previous experimental study did monitor suspended solid value despite of measuring attached biofilm on biological carrier surface to evaluate biomass in the reactor. Pure MBBR had MLVSS concentration in the bioreactor was similar to the influent value (Ahl, Leiknes, & Odegaard, 2006; Di Trapani, Mannina, Torregrossa, & Viviani, 2008; Leyva-Díaz et al., 2014). Suspended biomass concentration was relatively low and constant in total three sampling location for each RWTP, which indicate that biomass growth was homogenous throughout the IFAS biological tanks.

Turbidity Removal

The turbidity removal is shown as in figure 6 for 5 months monitoring respectively for all seven types of RWTP monitored.

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In the present study, the influent and effluent samples are collected from the RWTP location may exhibit large variations in the concentration of organic and inorganic matter leading to unstable results, as detected in the measurement during the initial observation period and the time required to reach steady state condition.

As indicated in the influent level of all RWTPs show a positive relationship between with TSS, meaning that a decrease in TSS concentration correlates with a decrease in turbidity levels. Thus, turbidity could provide a simple estimate of the TSS concentration in the river water despite not directly measuring of TSS in the water (Muhamad, Salim, Lau, Yusop, & Hadibarata, 2016). The efficiency of the RWTPs in reduction of turbidity is impressive. A percentage reduction in turbidity of over 90% could be achieved with an influent turbidity of 8.9 nephelometric turbidity unit (NTU). RWTP Sg Kemunsing shows the highest turbidity removal rate during June 2017 sampling and the lowest removal rate is at RWTP Sg Sering during Jun 2017 which as low as 9.8%. The removal efficiency ranking can be produced by calculating of mean pollutant removal. The average pollutant removal values were RWTP Kemunsing (56.15%) > RWTP Sg Belongkong (54.78%) > RWTP Sg Kemensah (48.92%) > RWTP Sg Gisir (38.68%) > RWTP Sg Klang (38.61%) > RWTP Sg Sering (29.80). This IFAS-RWTP can reduce turbidity to acceptable levels, and the effluent water can be achieved to NWQS Class II standard as initial target by the DID. However, this attached growth biological process suffers from such limitations as the excessive cost of equipment and biomedia and high aeration rate capacity. (Wilson et al., 2012).