Printer Friendly

Evaluation of Plastic Household Biosand Filter (BSF) In Combination with Solar Disinfection (SODIS) For Water Treatment.

Byline: Ghulam Hussain, Sajjad Haydar, Abdul Jabbar Bari, Javed Anwar Aziz, Mehwish Anis and Zunaira Asif

Summary

Efficiency of a household plastic biosand filter (BSF) for the removal of turbidity and fecal contamination was evaluated. Water of river Ravi was used as influent. Water filtered through BSF was further treated using Solar Disinfection (SODIS). The study was conducted for raw water with low pollution level (total coliforms less than 500 MPN/100 ml) and high pollution level (total coliforms between 500-20,000 MPN/100 ml). The average value of turbidity removal by BSF was 94.5 % with 0.9 NTU as average turbidity of effluent. For raw water with low pollution level, the BSF was able to achieve a maximum of 2.2 log10 unit reduction (99.4 %) for total coliforms (39 MPN/100 mL in effluent) and 1.95 log10 unit reduction (98.5 %) for fecal coliforms (9 MPN/100 mL in effluent). While for raw water with high pollution level, the maximum removal of 1.5 log10 unit (97.5 %) for total coliforms (1430 MPN/100 mL in effluent) and 1.8 log10 units (98.4 %) for fecal coliforms (387 MPN/100 mL in effluent) was achieved in BSF.

To make the effluent fit for drinking it was further treated using SODIS, which rendered the BSF effluent fit for drinking with zero fecal coliforms count (for full sunny and partially cloudy conditions). Newly proposed plastic BSF could be a good replacement of already used concrete household BSF (used in more than 63 countries) being cheaper in cost and lighter in weight by 85% and 80%, respectively than the concrete BSF.

Keywords: Biosand filter, Solar disinfection, Household water treatment, Coliforms, Turbidity, Removal efficiency.

Introduction

Globally, more than 780 million people still use unsafe drinking water sources [1]. Poor sanitation, water quality and hygiene practices have many serious consequences. Water borne diseases, in addition to deaths, make people less productive due to illness. Health systems are overburdened and national economies suffer. Sustainable development in a country is not possible without access to safe water, proper sanitation facilities, and personal hygiene.

In Pakistan, access to an improved water source increased from 85% in 1990 to 92% in 2010 [1]. Despite this improved access to water sources, the water is not safe to drink. Estimates show that 88% of the functional water supply schemes in Pakistan are providing unsafe drinking water to the consumers. The studies revealed four major water quality problems in the country i.e. Bacteriological (69%), Arsenic (24%), Nitrate (14%) and Fluoride (5%) [2]. This shows that the most common water quality issue in Pakistan is microbial contamination.

The development of low cost water treatment facilities have always been the point of concern for researchers and engineers. Many water treatment technologies are in vogue both at community and household level. Although these technologies have increased the access, of a large population, to safe drinking water supplies, but still the ultimate goal is not yet achieved.

A large number of options for water treatment are available in the developed countries, where monetary resources, technical expertise, materials and energy are abundantly available. The situation, however, is very grave in the developing countries where a large population has no access to piped and safe water. Deprived people are consuming water either from wells, hand pumps, and water brought from distant surface water sources.

A centralized system of water treatment might not be feasible for many areas due to dispersed population and poor water supply infrastructures. Therefore, the use of household water treatment methods may be a feasible alternative in such situations [3]. Some examples of currently used household water treatment technologies like biosand filters, solar disinfection, ceramic filtration, and boiling are proven to be useful.

The household biosand filter (BSF), originally developed by David Manz is an attractive water treatment option in developing countries [4]. This filter is a scaled down form of conventional slow sand filter, modified for intermittent use. The most studied BSFs have been those having concrete fabrication. The BSF has a number of advantages like simple design, durable material, local fabrication and provision of adequate quantities of water for household use [5]. The filters have a manufacturing cost ranging from US $10 to $ 30 [6], and there are no other costs for consumables or maintenance. There have been published trials which suggest that the concrete BSF can reduce diarrheal disease by 50% or greater [7-10].

In spite of the advantages of concrete BSF for household use, certain challenges limit its access to many users all over the developing world. These include high cost for some of the poorest households and cumbersome transport beyond initial installation site due to their weight which is as much as 250 Kg [11]. In addition, the research results presented in Table-1 show that water after treatment in BSF still needs further purification to completely remove the bacterial contamination. Little work has so far been carried out to further improve the microbial quality of BSF treated water using a low cost household technology.

The present research is undertaken with an aim to address above issues. Therefore, a cheap and light weight plastic material was selected to give an alternate to the high cost and heavy concrete household BSF. Furthermore, additional treatment using Solar Water Disinfection (SODIS) was used to improve the microbial quality of BSF treated water and to evaluate whether it becomes fit for drinking purpose.

Experimental

Filter Setup

Instead of concrete, a plastic container was used in this research work to construct a household BSF. The total volume of the plastic container was 30 L (costing US$ 1.5). The filtration media was selected as per instructions provided by CAWST [6]. Sand of two sources; river Ravi and river Chenab, was sieved through different mesh screens to check their adequacy for use as filter media for BSF. Results of the sieve analysis are presented in Table-2. The suitability of sand from the above mentioned sources was evaluated on the basis of effective size and uniformity coefficient. These two parameters were calculated from the results of sand sieve analysis. A graph is plotted between sieve size (mm) and % weight passing. Effective size is D10 (i.e. size at 10 % weight passing) and Uniformity coefficient is D60/D10 (i.e. ratio of size at 60% and 10% weight passing).

Results are shown in Table-3. As shown in Table-3, Ravi sand was found most suitable (effective size = 0.14 mm, and uniformity coefficient = 2.15). It provided an initial flow rate of 36 liters/hour (L/hr). The recommended filtration rate for household BSF is also 36 L/hr [6]. The dimensions and media specifications for the plastic biosand filter are shown in Fig. 1.

The proposed plastic biosand filter consists of a plastic bucket. Filter media consist of sand layer of 15 cm depth. Sand layer was supported with gravel having a size range of 6-15 mm with a total depth of 5 cm. A sieved plastic basket was used as flow diffuser to protect biolayer from disturbance when water is poured. A PVC outlet pipe with tap as shown in Fig. 1 maintained a certain minimum water level (2 cm) above sand layer to sustain biological life in the top layer allowing the filter to operate intermittently. Filter also contained a lid to avoid external contamination.

Table-1: Summary of Contaminant Removal Efficiency by Concrete BSF (past studies).

Sr. No.###Contaminant/ Parameter###Average Removal Efficiency (%)###Study Place###Reference

###1###Fecal coliforms###96% (range 91.1 to 99.7%)###Laboratory###[15]

###99 %

###protozoan parasites, heterotrophic bacteria,

###2###83 %###Laboratory###[16]

###organic and inorganic chemicals

###50-90 %

###3###total coliforms###99.5 %###Laboratory###[17]

###94 %###Laboratory

###4###E. coli###[18]

###93%###Field

###5###fecal coliforms###99.5 %###Field###[4]

###6###fecal coliforms###93%###Field###[19]

###total coliforms,###98.6 %

###7###E. coli,###97.3 %###Field###[20]

###Turbidity###85 %

###8###E. coli###98.5 %###Field###[3]

###9###E. coli###87.9 %###Field###[21]

###10###E. coli###97 %###Field###[22]

###11###E. coli###83 %###Field###[7]

###12###E. coli###97 %###Field###[23]

###E. coli

###13###88-89 %###Field###[10]

###Total coliforms

###Bacteria###96 %

###14###Virus###71 %###Laboratory###[24]

###Turbidity###89 %

Table-2: Results of sand sieve analysis/experiment.

###RAVI SAND

###Sample No. 1###Sieve No.###Wt. Retained###% Retained###% Cumulative###% Passing

###Source:###3/4###-###-###-###-

###Ravi Sand###4###-###-###-###-

###10###-###-###-###100

###40###43.02###14.34###14.34###85.66

###Sample weight = 300 g

###100###220.83###73.61###87.95###12.05

###200###31.88###10.62###98.57###1.43

###CHENAB SAND

###Sample No. 2###Sieve No.###Wt. Retained###% Retained###% Cumulative###% Passing

###Source:###3/4###-###-###-###-

###Chenab Sand###4###-###-###-###-

###10###-###-###-###100

###40###22.82###7.6###7.6###92.4

###Sample weight = 300 g

###100###179.83###59.94###67.54###32.46

###200###91.07###30.35###97.89###2.11

Table-3: Results for effective size and uniformity coefficient derived from sieve analysis.

###Sample###Effective Size, D10###Uniformity Coefficient, U.C

###Ravi###0.14 mm###2.15

###Chenab###0.09 mm###2.55

###Criteria for BSF###0.1 to 0.25 mm

###1.5 to 2.5

###(CAWST, 2008)###(preferred 0.1 to 0.2 mm)

Table 4: Phasing of Experimental Work.

###Coliforms Range

###Phase###Dates###Influent water###Pollution Level

###(MPN/100 mL)

Phase-1 (8 Weeks)###13.01.12 to 02.03.12###River water diluted with tap water###0 500###Low

Phase-2 (8 Weeks)###09.03.12 to 04.05.12###Settled river water###500 20,000###High

After preparing the filter, initial flow rate was measured by filling the space above the sand bed (up to 10 cm depth) to its full capacity and noting the time to fill a graduated container by drawing water through the filter outlet. The initial flow rate at first filter run was measured to be 36 L/hr (equivalent to filtration/hydraulic loading rate of 12 m3/m2-d). Fig.2 shows a picture of the constructed biosand filter.

Sample Collection and Filter Dosing

Raw influent water used for the experiments was collected from river Ravi. Filter dosing was done with 20 L of water manually, twice a day, for about 16 weeks. A pause period of 12 to 24 hours was provided between each filter dosing. The purpose of pause period was to provide sufficient time for consumption of bacteria entrapped in the biolayer. The total duration of experimentation was divided into two Phases, each of eight weeks, as shown in Table-4.

For Phase-1, raw river water was diluted by mixing tap water to reduce the concentration of indicator organisms prior to filter dosing; this diluted water was termed as water with low pollution level (coliforms count less than 500 MPN/100 mL). In Phase-2, settled raw river water without any dilution was applied to the filter for a period of eight weeks. This raw water is termed as water with high pollution level (coliform count 500 20,000 MPN/100 mL). Settlement was done for 0.5 to 1 hr to reduce the turbidity of raw river water below 50 NTU [6]. The rationale for dividing the study into two phases was to evaluate the performance of filter for these two types of waters. These two phases helped to assess the performance of BSF and SODIS for two levels of microbial contamination normally encountered i.e. low levels found in shallow wells, hand pumps or other ground sources, and high levels usually observed in surface waters.

Raw and filtered water from both the Phases was examined for total and fecal coliform count, and turbidity on weekly basis. The flow rate of water through the filter was also measured with the same frequency.

SODIS Procedure

The results of previous studies presented in Table-1 show that BSF removes most of the suspended impurities. However, complete removal of bacteriological contamination is not possible with BSF alone. BSF could not produce water fit for drinking as per WHO guidelines which state that thermotolerant (fecal) coliforms should be zero [13]. Thus further treatment is required. SODIS was selected and used as post treatment technology in this study. SODIS technique is specially targeted to remove bacteriological contamination. This technique is cheap and can easily be practiced in developing countries by low income households. To evaluate SODIS as post treatment technology, filtrate of BSF was collected in sterile PET bottles and subjected to solar radiations. Solar disinfection (SODIS) was evaluated based on its efficacy for the removal of indicator organisms. The filtrate from BSF was treated through SODIS by the following procedure with a pictorial view in Fig. 3.

Water was collected in clean sterilized PET bottles.

Agitated well in contact with air (for about 2-3 min) to increase dissolved oxygen content.

Placed on the roof of Institute of Environmental Engineering and Research (IEER) for solar exposure.

Examined for total and fecal coliform counts after 2, 4, and 6 hours of solar exposure. Count was checked for three different durations to arrive at the minimum optimum time for SODIS.

The temperature of the water was also measured after 2, 4, and 6 hours of solar exposure.

Water Quality Analysis

Filtrate from the outlet of filter was collected in plastic containers for turbidity analysis, and in sterilized glass bottles for total and fecal coliforms analysis. Turbidity was measured by using Hach 2100 AN Turbidimeter". Multiple tube fermentation technique was used for total and fecal coliform count. All the tests were performed as per procedure laid down in Standard Methods for the Examination of Water and Wastewater" [14].

Water quality, after treatment with BSF and SODIS, was evaluated on the basis of WHO guidelines for drinking water i.e. Turbidity 5 NTU and Fecal Coliforms 0 /100mL [13].

Results and Discussion

Biosand Filter Performance

Performance of BSF was evaluated based on turbidity and indicator organisms' removal. In addition, flow rate, which is an important parameter of BSF operation, was also measured throughout the study period. The results of the study are presented in the following sections.

Flow Rate

The filter flow rate over the course of entire filter run (17 weeks) is presented in Fig 4. The Flow rate was measured when the water level in the filter was maximum, thus providing a constant head (10 cm) while measuring flow rate. Flow rate decreased considerably over time. The initial flow rate was about 30 L/Hr, and it declined to 18 L/Hr after 3 weeks of operation. Two possible reasons of reduced flow could be the development of biolayer (schmutzdecke) and high turbidity in the influent. But perhaps the most significant role was of the biolayer. Fluctuation of turbidity is shown in Fig. 5. It shows that turbidity kept varying with time. However, since the fluctuation of flow rate does not match with the turbidity fluctuation, therefore these two cannot be correlated.

After ripening, the magnitude of flow rate fluctuation reduced significantly. Nevertheless, the rate kept on reducing and hit 10 L/hr after a period of 17 weeks. At this point of time, a cleaning operation is required to restore the filtration rate.

Removal of Turbidity

The turbidity of raw water collected from river Ravi was in the range of 50 to 150 NTU. However, in both the phases, turbidity of influent water to filter was kept below 50 NTU, which is a pre-requisite for biosand filter [6]. Influent and effluent turbidity and the percent removal, for both the phases are presented in Fig. 5 and 6, respectively. Fig. 5 shows the measured values of turbidity for the influent and effluent water from the household BSF. It can be seen in the Fig that in spite of large variations in the turbidity of influent water (range: 8 38 NTU), the turbidity values of effluent were quite consistent (range 0.2 6 NTU), except for the first three weeks during which the filter ripening was taking place. In the third week, turbidity reduced to 1 NTU and thereafter remained lower than this value. The average value of effluent turbidity, over the study period, was 0.9 NTU which was less than the WHO guideline value of 5 NTU.

In Fig. 6, it can be observed that percentage removal for turbidity during the first two weeks varied from 66 % to 86 %. Filter ripening occurred during this period. From the third week, efficiency of the filter in removing turbidity improved significantly and lied in the range of 93 % to 99.4 %. This indicates that filter ripened after 3 weeks. The average value of percentage removal of turbidity, over the study period, was 94.5 %.

Removal of Coliforms

As discussed earlier, the filter run was divided into two phases. For Phase-1 (first eight weeks) filter was loaded with surface water of low pollution level. For the next eight weeks in Phase-2, the filter was loaded with water having high pollution level (see section experimental" for details).

PhaseI (water with low pollution level) Total and Fecal Coliforms Removal

Raw water collected from river Ravi was diluted with tap water and analyzed for total and fecal coliform counts. It was passed through the BSF and the filtrate was also examined for total and fecal coliforms count. Results of these experiments are presented in Table-5 and 6. Raw water analysis shows that total coliforms ranged from 150 to 420 MPN/100mL with an average value of 260 MPN/100mL. Fecal Coliforms in the raw water (influent) ranged from 17 MPN/100mL to 180 MPN/100mL with an average count of 81 MPN/100mL.

The analysis of filtrate revealed that for the first three weeks, removal of total coliforms was from 42 % to 80 %, whereas in fourth week of operation removal improved to 92.7 % (1.1 log10 reductions) which increased with time. It was deduced from these results that filter had ripened in about three to four weeks. Maximum removal was 99.4 % (2.2 log10 reductions) for total coliforms measured at eighth week of filter run. Similarly for fecal coliforms, removal was less in first three weeks (63 % to 93 %) and after ripening of filter, maximum percentage removal of fecal coliforms was 98.9 % (1.95 log10 reduction s) in the eighth week of filter run.

It can be deduced from Table-5 and 6 that Phase-1 water was not fit for drinking after BSF treatment as the fecal coliform count could not be reduced to zero. The coefficient of variation for influent shows less variation while for effluent the value is quite high that shows large fluctuation. It is due to the fact that filter performance at the initial stages was low and as it ripened, the performance was improved. This is true for both total and fecal coliforms removal.

Table-5: Removal of Total Coliforms by Plastic BSF.

###PHASE-1 (Low pollution level water)###PHASE-2 (High pollution level water)

Time

###Influent###Effluent###% age###Influent###Effluent###%age

(Weeks)###LRV###LRV

###(MPN/100mL) (MPN/100mL)###removal###MPN/100mL) (MPN/100mL)###removal

###1###320###170###46.9###0.3###16448###4025###75.5###0.6

###2###210###80###61.9###0.4###9562###1520###84.1###0.8

###3###170###34###80.0###0.7###11566###3621###68.7###0.5

###4###300###22###92.7###1.1###15000###1520###89.9###1.0

###5###150###4###97.3###1.6###6338###250###96.1###1.4

###6###420###4###99.0###2.0###5230###365###93.0###1.2

###7###200###2###99.0###2.0###1200###34###97.2###1.5

###8###315###2###99.4###2.2###2536###110###95.7###1.4

###Min###150###2###46.8###0.27###1200###34###68.69###0.50

###Max###420###170###99.4###2.20###16448###4025###97.17###1.55

###Avg.###260###39###84.5###1.29###8485###1430###87.51###1.05

Std Dev###92.68###58.97###20.0###0.77###5608###1593###10.54###0.39

###CV###35.6###151.2###23.7###59.7###66.1###111.4###12.0###37.1

Table-6: Removal of Fecal Coliforms by Plastic BSF.

###PHASE-1 (Low pollution level water)###PHASE-2 (High pollution level water)

Time

(Weeks)###Influent###Effluent###%age###Influent###Effluent###%age

###LRV###LRV

###(MPN/100mL) (MPN/100mL)###removal###(MPN/100mL) (MPN/100mL)###removal

###9###80###34###57.5###0.37###8050###1540###80.9###0.72

###10###70###26###62.9###0.43###6500###1050###83.8###0.79

###11###17###2###88.2###0.93###1235###265###78.5###0.67

###12###85###6###92.9###1.15###1230###120###90.2###1.01

###13###60###2###96.7###1.48###2590###70###97.3###1.57

###14###40###2###95.0###1.30###860###14###98.4###1.79

###15###120###2###98.3###1.78###268###6###97.8###1.65

###16###180###2###98.9###1.95###1540###35###97.7###1.64

###Min###17###2###57.5###0.37###268###6###78.5###0.67

###Max###180###34###98.9###1.95###8050###1540###98.3###1.79

###Avg.###81###9###86.3###1.17###2784###387###90.5###1.23

Std Dev###50.25###12.91###16.5###0.58###2877###581###8.39###0.48

###CV###62###143.4###19.1###49.6###103.3###150.1###9.3###39.0

Phase-2 (water with high pollution level) Total and Fecal Coliforms Removal

In Phase-2, filter was dosed with raw river water without any dilution (high pollution level). Prior to the application of this water to BSF, it was settled (for about 2 to 5 hours depending upon influent turbidity) to achieve a turbidity lesser than 50 NTU. Water was analyzed for total coliforms and fecal coliforms before and after BSF treatment. Results of analysis for total and fecal coliforms are presented in Table-5 and 6.

It can be seen in Table-5 that total coliforms concentration in the settled influent varied greatly from 1200 to 16,448 MPN/100 mL with an average value of 8485 MPN/100 mL. While, in the filtered water, total coliforms ranged from 34 to 4025 MPN/100 mL with an average value of 1430 MPN/100 mL.

It is evident from Table-5 that the removal of total coliforms varied in a range of 69 % (0.5 log10 reduction); at the start of filter run to 97.2 % (1.55 log10 reduction) in the 15th week of filter run. The average removal was 87.5 % (log10 reduction of 1.05). The mean concentration of total coliforms in the effluent was 34 MPN/100 mL. Similarly, fecal coliforms removal varied from 78.5 % (0.67 log10 reduction) to 98.3 % (1.79 log10 reduction). The average removal was 90.5 % (1.23 log10 reduction). The mean concentration of fecal coliforms in the effluent was 6 MPN/100 mL. It shows that Phase-2 water was not fit for drinking after BSF treatment. It can also be seen in Table-5 and 6 that the influent total and fecal coliforms count kept varying. The count in the treated water increased with high values of count in the influent and decreased with low count in the influent. However, the removal efficiency of the filter increased with the passage of time and got better at the end of filter run.

Therefore, it can be inferred that the filter efficiency improve with run, perhaps may be due to increase in the number o microorganism that prey on the total and fecal coliforms. Another reason may be increase in filtering/screening capacity due to blockage of larger pores with the passage of time.

Solar Disinfection of Biosand Filtrate

The results presented above show that BSF could not produce water fit for drinking as per WHO guidelines which state that fecal coliforms should be zero. Thus further treatment was required. For this purpose, filtrate of BSF was collected in sterile PET bottles and subjected to SODIS. Samples were analyzed after 1.5, 3, 4.5 and 6 hours of solar exposure for total and fecal coliform count. The results are discussed in the following sections.

Removal of Total Coliforms for BSF treated water

Removals of total coliforms by SODIS for the filtrate of BSF, for water with low and high level of pollution are presented in Table-7. For water with low level of pollution, it can be seen in the table that total coliforms reduced to zero, except for one sample, after 6 hours of exposure to sunlight. This sample was not exposed to proper sunlight due to cloudy conditions on that day. For water with high pollution levels, total coliform count reduced to zero except two samples. Reason of the presence of total coliforms in these two samples may be the cloudy atmosphere when these samples were subjected to SODIS. Thus 75 percent samples were free of total coliform count.

From Table-7, it is evident that the combined BSF and SODIS treatment is quite effective in removing total coliforms. A sunny day and 6 hours exposure appears to be the optimal conditions. However, cloudy conditions with 6 hours exposure could not result in zero count.

Table 7: Total Coliforms Removal in BSF and SODIS When Applied in Combination.

###Coliforms at BSF Turbidity after###Coliforms (MPN/100 mL) after

###Temp###Overall R.E

Date###Atmosphere###(MPN/100 mL)###Filtration###SODIS Exposure (Hrs)

###o###(%)

###C###Influent Effluent###(NTU)###1.5###3###4.5###6

###Less pollution level water (BSF treated)

13-01-12###18###Full Sunny###320###185###2###52###12###0###0###100.0

20-01-12###16###Full Sunny###210###109###1.3###25###1###0###0###100.0

27-01-12###18###Partially Cloudy###170###37###0.9###20###12###2###0###100.0

3/2/2012###17###Cloudy###300###23###0.4###15###8###4###4###98.7

10/2/2012###19###Full Sunny###150###3###0.3###0###0###0###0###100.0

17-02-12###18###Partially Cloudy###420###4###0###2###0###0###0###100.0

24-02-12###21###Partially Cloudy###200###3###0.3###1###1###0###0###100.0

2/3/2012###26###Partially Cloudy###315###1###0.5###0###0###0###0###100.0

###High pollution level water (BSF treated)

9/3/2012###23###Full Sunny###16448###4025###0.3###1050###420###75###0###100.0

16-03-12###26###Partially Cloudy###9562###1520###0###850###212###35###0###100.0

23-03-12###28###Full Sunny###11566###3621###0###960###254###90###0###100.0

30-03-12###32###Partially Cloudy###15000###1520###0###650###230###110###0###100.0

6/4/2012###34###Partially Cloudy###6338###250###0###360###124###23###0###100.0

13-04-12###32###Cloudy###5230###365###0###235###185###88###65###98.8

20-04-12###35###Cloudy###1200###560###1.5###400###254###75###85###92.9

4/5/2012###36###Full Sunny###2536###1200###1###300###125###80###0###100.0

Table-8: Fecal Coliforms Removal in BSF and SODIS When Applied in Combination.

###Coliforms at BSF###Turbidity after Coliforms (MPN/100 Ml) after

###Temp###Overall R.E

Date###o###Atmosphere###(MPN/100 mL)###Filtration###SODIS Exposure (Hrs)

###C###(%)

###Influent###Effluent###(NTU)###1.5###3###4.5###6

###Less pollution level water (BSF treated)

13-01-12###18###Full Sunny###79###35###2###12###2###0###0###100.0

20-01-12###16###Full Sunny###70###30###1.3###10###4###0###0###100.0

27-01-12###18###Partially Cloudy###17###1###0.9###1###0###0###0###100.0

3/2/2012###17###Cloudy###85###12###0.4###9###5###2###6###92.9

10/2/2012###19###Full Sunny###64###6###0.3###2###0###0###0###100.0

17-02-12###18###Partially Cloudy###45###3###0###2###0###0###0###100.0

24-02-12###21###Partially Cloudy###120###1###0.3###0###0###0###0###100.0

2/3/2012###26###Partially Cloudy###180###2###0.5###1###0###0###0###100.0

###High pollution level water (BSF treated)

9/3/2012###23###Full Sunny###8050###1540###0.3###256###120###42###0###100.0

16-03-12###26###Partially Cloudy###6500###1050###0###752###465###120###0###100.0

23-03-12###28###Full Sunny###1235###265###0###152###70###10###0###100.0

30-03-12###32###Partially Cloudy###1230###120###0###105###95###10###0###100.0

6/4/2012###34###Partially Cloudy###2590###75###0###45###12###12###0###100.0

13-04-12###32###Cloudy###860###15###0###12###5###4###6###99.3

20-04-12###35###Cloudy###268###120###1.5###85###25###14###6###97.8

4/5/2012###36###Full Sunny###1540###635###1###189###76###45###0###100.0

Removal of Fecal Coliforms for BSF treated water

Removals of fecal coliforms by combined BSF and SODIS treatment, for water with low and high level of pollution, are presented in Table-8. It is evident that for water with low pollution level, sunlight exposure of 4.5 hours is sufficient"after BSF treatment to reduce the count to zero. However, BSF treated water with high pollution level requires sunlight exposure of 6 hours to reduce the fecal coliform count to zero. Furthermore, it was also observed that cloudy condition can affect SODIS and required degree of treatment may not be achieved.

Comparison of Plastic BSF with Concrete BSF

As of June, 2012 more than 430,000 concrete BSF are in use, installed in more than 63 countries [12]. The cost and weight of newly proposed household plastic BSF has been compared with concrete BSF in Fig. 7. It can be seen in Fig. 7 that the cost of plastic biosand filter is US $ 3 which is only 15 percent of the average cost of concrete biosand filter i.e. US $ 20 [6]. Hence it is much more affordable for use for low income communities. Furthermore, plastic BSF is much easy to move around due its less weight as compared to concrete BSF. The weight of proposed plastic BSF is just 20 percent (50 Kg) of the weight of concrete BSF i.e. 250 Kg [11].

Conclusions

Following conclusions and recommendations can be drawn from this research work.

The initial efficiency of BSF for the removal of turbidity and bacteriological contamination is low. However, it improves with operation time and reaches its optimal value after about three weeks of operation when Schmutzdecke layer develops fully. The filtration rate reduced after three weeks however was sufficient to meet drinking water requirements of a household.

Average percentage removal of turbidity of household BSF was 94.5% with filtrate turbidity of less than 1 NTU

At its optimal operation, the average percentage removal of household BSF for total and fecal coliforms was 84.5% (1.29 log10 reduction) and 86.3% (1.17 log10 reduction) respectively for water with low pollution level. Average percentage removal of total and fecal coliforms was 87.5% (1.05 log10 reduction) and 90.5% (1.23 log10 reduction) respectively for water with high pollution level. However, the treated water could not qualify the WHO guidelines for drinking water quality.

BSF and SODIS, when applied in combination, demonstrated a maximum removal of 4.2 log reductions (100 %) for total and 3.9 log reductions (100 %) for fecal coliforms for full sunny and partially cloudy conditions. Thus a combined BSF-SODIS treatment could produce water fit for drinking purpose for the raw water used in this study. The optimal conditions for SODIS were exposure of 4.5 hours for water with low pollution level and 6 hours for water with high pollution level.

For full cloudy conditions, BSF-SODIS method was unable to remove the bacteriological contamination from water for the exposure duration used in this study.

The proposed plastic household BSF is cheaper as compared to the presently used concrete BSF. The cost for proposed plastic BSF is US $ 3 (PKR 300) while average costs of concrete BSF is US $ 20. In addition, it is also lighter with a weight of 50 Kg as compared to concrete BSF having a weight of 250 Kg; thus making it easily portable. The expected life of the filter depends on the quality of plastic used in its manufacturing and whether it is handled and operated carefully.

BSF in combination with SODIS is recommended for household level of water treatment for surface water as well as ground/shallow well waters. The complete treatment unit recommended for polluted surface water is shown below in Fig. 8.

References

1. JMP, WHO/UNICEF Joint Monitoring Program for Water Supply and Sanitation, Progress Report (2012).

2. PCRWR, National Water Quality Monitoring Program (NWQMP: 2002-06), Pakistan Council of Research in Water Resources Publication No.143-2010, (2010).

3. W. Duke and D. Baker, A Field Study of 107 Households. Victoria: University of Victoria, (2006).

4. D. Manz, B. Buzunis and C. Morales, Nicaragua Household Water Supply and Testing Project, (1993).

5. M. Sobsey, C. E. Stauber, L. M. Casanova, J. M. Brown and M. A. Elliott, Point of Use Household Drinking Water Filtration: A Practical, Effective Solution for Providing Sustained Access to Safe Drinking Water in the Developing World, Environ. Sci. Technol, 42, 4261 (2008).

6. CAWST, Biosand Filter Manual, Centre for Affordable Water and Sanitation Technologies, Canada (2008).

7. C. E. Stauber, G. M. Ortiz, D. P. Loomis, M. D. Sobsey, A Randomized Controlled Trial of the Concrete Biosand Filter and its Impact on Diarrheal Disease in Bonao, Dominican Republic, Am. J. Trop. Med. Hyg., 80, 286 (2009).

8. S. Tiwari, W. P. Schmidt, J. Darby, Z. G. Kariuki and M. W. Jenkins, Intermittent Slow Sand Filtration for Preventing Diarrhea among Children in Households Using Unimproved Water Sources: A Randomized Controlled Trial Trop Med Int Health, 14, 1374 (2009).

9. K. Liang, M. Sobsey and C. Stauber, Improving Household Water Quality; Use of Biosand Filters in Cambodia, Water and Sanitation Program, Cambodia (2010)

10. B. A. Aiken, C. E. Stauber, G. M. Ortiz and M. D. Sobsey, An Assessment of Continued Use and Health Impact of the Concrete Biosand Filter in Bonao, Dominican Republic Dominican Republic, Am. J. Trop. Med. Hyg., 85, (2011).

11. T. Clasen, World Health Organization: Geneva, Switzerland WHO/HSE/WSH/09.02; (2009).

12. CAWST, Biosand Filter, Centre for Affordable Water and Sanitation Technologies, Canada, (2012).

13. WHO, Guidelines for Drinking Water Quality: Fourth Edition, World Health Organization, (2011).

14. A. D. Eaton, L. S. Clesceri, A. E. Greenberg, M. A. H. Franson, American Public Health Association, American Water Works Association, and Water Environment Federation, Standard Methods For The Examination Of Water And Wastewater, American Public Health Association, Washington, DC, (1998).

15. B. J. Buzunis, M.Sc. Thesis, Intermittently Operated Slow Sand Filtration: A New Water Treatment Process, University of Calgary, Canada (1995).

16. G. Palmateer, D. Manz, and A. Jurkovic, Toxicant and Parasite Challenge of Manz Intermittent Slow Sand Filter, Environ. Toxicol, 14, 217 (1999).

17. T. L. Lee, M.Sc. Thesis, Biosand Household Water Filter Project in Nepal, Massachusetts Institute of Technology, Boston (2001).

18. C. E. Stauber, M. A. Elliott, F. Koksal, G. M. Ortiz, F. A. DiGiano and M. D. Sobsey, Characterization of the Biosand Filter for E. coli Reductions from Household Drinking Water Under Controlled Laboratory and Field Use Conditions, Wat. Sci. Tech, 54, 1 (2006).

19. N. Kaiser, K. Liang, M. Maertens and R. Snider, A Comprehensive Evaluation of the Samaritan's Purse Biosand Filter (BSF) Projects in Kenya, Mozambique, Cambodia, Vietnam, Honduras and Nicaragua: Samaritan's Purse Canada (2002).

20. M. Maertens and A. Buller, Kale Heywet Ethiopia Household Water and Sanitation Project Evaluation, Paper presented at the University of North Carolina Safe Drinking Water, Chapel Hill, North Carolina (2006).

21. P. Earwaker, M.Sc. Thesis, Evaluation of Household Biosand Filters in Ethiopia, Cranfield University, Silsoe (2006).

22. J. Vanderzwaag, M.Sc. Thesis, Use and Performance of BioSand Filters installed in Posoltega, Nicaragua: A Field Evaluation, University of British Columbia (2007).

23. J. C. Vanderzwaag, J. W. Atwater, K. H. Bartlett, and D. Baker, Field Evaluation of Long-Term Performance and Use of Biosand Filters in Posoltega, Nicaragua, Water Qual Res J Can, 44, 111 (2009).

24. M. W. Jenkins, S. K. Tiwari and J. Darby, Bacterial, Viral and Turbidity Removal by Intermittent Slow Sand Filtration for Household Use in Developing Countries: Experimental Investigation and Modeling, Water Res., 45 (2011).
COPYRIGHT 2015 Asianet-Pakistan
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2015 Gale, Cengage Learning. All rights reserved.

 
Article Details
Printer friendly Cite/link Email Feedback
Author:Hussain, Ghulam; Haydar, Sajjad; Bari, Abdul Jabbar; Aziz, Javed Anwar; Anis, Mehwish; Asif, Zunaira
Publication:Journal of the Chemical Society of Pakistan
Article Type:Report
Date:Apr 30, 2015
Words:5995
Previous Article:Tidal Flushing Characteristics of Municipal and Industrial Waste in the Karachi Coastal Waters and Simulation of Waste Field Dilution at Sewage...
Next Article:Preparation, Morphologies and Properties of Multiwalled Carbon Nanotubes-Filled PMMA/PVC Blends.
Topics:

Terms of use | Privacy policy | Copyright © 2018 Farlex, Inc. | Feedback | For webmasters