Table 16 Maintenance of oxidation and filtration technologies

Modified Garnet home-made filter

Maintenance - Sand and chips contaminated with As to be washed and disposed of.

Positive - Users appreciated the quality and taste of the water, and its transparency because it was free of iron (Amin, 2010).

Acceptance satisfactory, particularly with plastic containers as opposed to earthen containers (Hoque et al., 2000).

Negative - Most of the women who operated the filters, faced difficulties reinstalling them. For the washing and drying of the filter materials and moving of the buckets, they needed assistance from other household members. The case studies also revealed that many household heads were not willing to buy the materials (Amin, 2010).

After three months, most of the filters were found to be dirty and without lids and the buckets for storing water were covered by a dirty cloth. Out of eight, five were under operational conditions. Three filters had changed filter bed materials and were treated according to the instructions, whereas two filters, the materials were only washed without changing them. The users of three filters had stopped operation of the filters after two to three months (Amin, 2010).

Two households did not replace the filter bed materials. They reused the materials after washing them, rinsed with Ca(ClO)₂ and dried them. For the remaining six households, the disposal of the spent filter materials was carried out in different ways. Two households threw the spent filters materials at the back of their houses on the land. One household used the filter bed materials in construction work and one household replaced the spent materials with new sand and brick chips in the shop for free. The other two households disposed of the spent materials on the cow dung stockpile near their house and covered them with cow dung (Amin, 2010).

Slow flow rates, not enough As free water and heavy to use (Hoque et al., 2004).

Sand filter

Maintenance – Sand is replaced and tanks cleaned with a brush every one to two months

Positive - Users of the community-based option found it technically effective. A keen interest was shown because it was less exposed to outside contaminants compared to the three-pitcher. Also employs indigenous technology (BRAC, 2000).

The visually observable removal of iron from the pumped water makes the effect of sand filters recognisable even to people who are not aware of the arsenic problem. Eighty-two percent of respondents with sand filters would decide again in favour of it. Of households without sand filters, 36% would decide in favour of it. Forgetting the maintenance does not seem to be a problem since a reduction in water flow and change in colour and taste act as natural reminders (Tobias and Berg, 2011).

Negative - Users have to wait until reservoir is full to use. High initial installation costs. Needs continuous monitoring for clogging and arsenic removal capacity. Chambers need to be covered properly to protect from insects which may put people off (BRAC, 2000).

Problems with space requirement, weight or immobility, and practical problems, such as pumping and filter repair. Other projects like building a new room, buying appliances where given a priority over sand filters. Respondents reported changing the sand in the filters every three to four months. This is near the recommended frequency of changing the sand every three months. However, 52% changed it less frequently (Tobias and Berg, 2011).

Home based filter (3 pitcher)

Maintenance - Unit to be washed every seven to ten days.

Ardasha filter

-

Passive sedimentation

Positive - High acceptance from users (Hoque et al., 2004).

SPACE AIRPs

Maintenance - This technology requires cleaning which Brennan and McBean (2011) state users are capable of doing.

AIRPs

Maintenance - Filtration media requires backwashing 2–3 times per week. No current methods of disposal for As contaminated sludge.

Positive - From a survey of 200 users, 100% were willing to use the system and willing to pay. Only 4% complained about the maintenance (Abdullah and Rumana, 2006).

Negative - The tubewells and the ARPs belonged to different manufacturers and the matching was often poor, leading to jammed valves, longer collection time, erupting water drenching user (Hossain et al., 2006).

Clogging of ARPS due to sand gushing. Another problem in running ARPs is clogging, which happens due to silvery colloidal sand coming in with water and choking the tubewell and filter media. The ARP manufacturers and the installing authority did not consider this before installation. Each ARP has a fixed media life and after that the media needs to be changed for consistent performance. It was observed that many ARPs required changing their media well before adsorptive capacity due to clogging (Hossain et al., 2006).

Only 30% of the 432 operational ARPs received regular backwashing, but only 10 out of 131 regularly backwashed ARPs were being backwashed twice a week, which is necessary for efficient performance (Hossain et al., 2006).

Domestic clay candle filter

-

Iron oxidising bacteria

Maintenance - May be operated for 4–7 months without cleaning. If cleaned but not maintained, authors estimate may operate for five to ten months.

Positive - One person found the operation and maintenance tedious, although this became easier following gradual modifications resulting in improved effluent flow and reduced cleaning frequency (Hassan et al., 2009).

Negative - Use of calcium hypochlorite on AIRUs with high As influent concentration caused an objectionable odour (Hassan et al., 2009).

A/IRU

Maintenance - Cleaning was performed by opening the gate valve at the bottom layer of the up flow roughing filter and flushing out settled sludge through backwashing by hydrostatic pressure.

Positive - From a survey of 200 users, 100% were willing to use the system and willing to pay. Only 4% complained about the maintenance (Abdullah and Rumana, 2006).

Negative - The tubewells and the ARPs belonged to different manufacturers and the matching was often poor, leading to jammed valves, longer collection time, erupting water drenching user (Hossain et al., 2006).

Iron removal ceramic filter

Maintenance - Users cleaned filter once a week with hot water and soft cloth or brush.

Positive - 80% users reported that the filter was easy to maintain and filtered water appeared clear, tasted better and odourless. Ninety percent used it for one year and were satisfied with it (Shafiquzzaman et al., 2011).

Asian Arsenic Network (AAN) Filter

Maintenance - Replacement of sand in second pitcher after two months.

Negative - Removal efficiency of As and flow rate decreased greatly after three month continuous operation (Delowar et al., 2006).

NIFSF

Maintenance - Package and storage (of bleach in particular which has a shelf life of two months).

Negative - As removal efficiency substantially decreased after two month continuous operation. Issue with proper packaging and storage particularly of bleaching powder having a very limited shelf life (only two months) (Delowar et al., 2006).