Under the Residential Tenancy Act you have the right to quiet and safe enjoyment of the premises. You can issue a written notice to your landlord requesting him to rectify the situation
immediately or terminate the Lease. This might worsen your co-habitual relationship with your roommates, so that may not be the appropriate option, but you be the judge of that risk. If the Landlord threatens them to terminate their Lease and keep the deposit, they might smarten up.
Other option is to issue a notice to the Landlord terminating the tenancy for non-sanitary living conditions and request your damage deposit return in full. If he refuses, arm yourself with photographs and file a complaint with
RTDA.