Household water use and greywater management in Khulna city, Bangladesh.

While substantial progress has been made in improving water and sanitation services in low- and middle-income countries, aligned basic services such as greywater, stormwater, and solid waste management have progressed little in recent decades. Data was collected in Khulna city, Bangladesh via a household survey (n = 192) of low-income areas exploring domestic water use and greywater volumes, characteristics, and disposal practices. Most households (71%) use a piped water supply for domestic purposes, supplemented by seasonal rainwater harvesting (26%) and greywater use (13%). Of the total water used by households (mean: 594 L/household/day and equivalent to 116 L/person/day), approximately 58% becomes greywater through bathing, dishwashing, religious practices, handwashing, laundry, and mopping. Greywater produced ranges from 61-1274 L/household/day, with a mean of 345 L/household/day and equivalent to 78.4 L/person/day. Greywater characteristics vary depending on the activity, individual behaviours and any products used during cooking, bathing, or cleaning. After generation, households dispose greywater to open drains (67%), nearby waterbodies (17%) directly to the ground (9%), or decentralised wastewater treatment system (7%). Without services for greywater management, greywater disposal may have considerable public and environmental health implications, necessitating careful attention and oversight from service-providers and stakeholders beyond the household-level.

Genetic variation in wild and hatchery populations of giant freshwater prawn (Macrobrachium rosenbergii) revealed by randomly amplified polymorphic DNA markers.

Sustainable improvement and conservation of any genetic resource depend on the assessment of its intra- and inter-population genetic variation. In order to estimate genetic variation in both wild and hatchery populations of Macrobrachium rosenbergii, randomly amplified polymorphic DNA (RAPD) analysis was performed. Analyses of 51 polymorphic loci amplified from genomic DNA by three decamer random primers revealed different degrees of genetic variation in two wild (Bhairab and Rupsha rivers) and hatchery-derived gher (Gher-1 and Gher-2) populations. The proportion of polymorphic loci was found to be higher in wild populations (0.90 and 0.65 for the Bhairab and Rupsha populations, respectively) than the hatchery-derived gher populations (0.29 and 0.16 for Gher-1 and Gher-2, respectively). Likewise, the river populations contained higher levels of gene diversity (0.221 and 0.179 for Bhairab and Rupsha populations, respectively) than the gher populations (0.114 and 0.045 for Gher-1 and Gher-2, respectively). These results suggest reduction of genetic variation and heterozygosity in the hatchery-derived gher populations. Inter-population similarity indices and pairwise genetic distance values showed that variation between the wild or between the gher populations were lower than those between the wild and hatchery populations. On average, 14 loci exhibited significant deviation from homogeneity in wild vs hatchery population pairs, whereas 2 and 3 loci showed heterogeneity in Gher-1 vs Gher-2 and Bhairab vs Rupsha population pairs, respectively. A genetic distance-based UPGMA dendrogram segregated river populations from the gher populations. Our study, therefore, revealed substantial levels of genetic variation between wild and hatchery populations of M. rosenbergii.